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Alfred Korzybski | Further reading | Further reading
Kodish, Bruce. 2011. Korzybski: A Biography. Pasadena, CA: Extensional Publishing. softcover, 978-09700664-28 hardcover.
Kodish, Bruce and Susan Presby Kodish. 2011. Drive Yourself Sane: Using the Uncommon Sense of General Semantics, Third Edition. Pasadena, CA: Extensional Publishing.
Alfred Korzybski, Manhood of Humanity, foreword by Edward Kasner, notes by M. Kendig, Institute of General Semantics, 1950, hardcover, 2nd edition, 391 pages, . (Copy of the first edition.)
Science and Sanity: An Introduction to Non-Aristotelian Systems and General Semantics, Alfred Korzybski, preface by Robert P. Pula, Institute of General Semantics, 1994, hardcover, 5th edition, . (Full text online.)
Alfred Korzybski, Collected Writings 1920-1950, Institute of General Semantics, 1990, hardcover,
Montagu, M. F. A. (1953). Time-binding and the concept of culture. The Scientific Monthly, Vol. 77, No. 3 (Sep., 1953), pp. 148–155.
Murray, E. (1950). In memoriam: Alfred H. Korzybski. Sociometry, Vol. 13, No. 1 (Feb., 1950), pp. 76–77. |
Alfred Korzybski | External links | External links
Alfred Korzybski and Gestalt Therapy Website
Australian General Semantics Society
Institute of General Semantics
Finding aid to Alfred Korzybski papers at Columbia University. Rare Book & Manuscript Library.
Category:1879 births
Category:1950 deaths
Category:Writers from Warsaw
Category:Clan Abdank
Category:Polish emigrants to the United States
Category:Polish engineers
Category:20th-century Polish philosophers
Category:Polish mathematicians
Category:Linguists from Poland
Category:General semantics
Category:People from Lakeville, Connecticut |
Alfred Korzybski | Table of Content | Short description, Early life and career, General semantics, "To be", Anecdotes, Influence, Publications, See also, References, Further reading, External links |
Asteroids (video game) | Short description | Asteroids is a multidirectional shooter video game developed and published by Atari for arcades. It was designed by Lyle Rains and Ed Logg. The player controls a single spaceship in an asteroid field which is periodically traversed by flying saucers. The object of the game is to shoot and destroy the asteroids and saucers, while not colliding with either, or being hit by the saucers' counter-fire. The game becomes more difficult as the number of asteroids increases.
Asteroids was conceived during a meeting between Logg and Rains, who decided to use hardware developed by Wendi Allen (then known as Howard Delman) previously used for Lunar Lander. Asteroids was based on an unfinished game titled Cosmos; its physics model, control scheme, and gameplay elements were derived from Spacewar!, Computer Space, and Space Invaders and refined through trial and error. The game is rendered on a vector display in a two-dimensional view that wraps around both screen axes.
Asteroids was one of the first major hits of the golden age of arcade games; the game sold 47,840 upright cabinets and 8,725 cocktail cabinets and proved both popular with players and influential with developers. In the 1980s it was ported to Atari's home systems, and the Atari VCS version sold over three million copies. The game was widely imitated, and it directly influenced Defender, Gravitar, and many other video games. |
Asteroids (video game) | Gameplay | Gameplay
thumb|left|A ship is surrounded by asteroids and a saucer.
The objective of Asteroids is to destroy asteroids and saucers. The player controls a triangular ship that can rotate left and right, fire shots straight forward, and thrust forward. Once the ship begins moving in a direction, it will continue in that direction for a time without player intervention unless the player applies thrust in a different direction. The ship eventually comes to a stop when not thrusting. The player can also send the ship into hyperspace, causing it to disappear and reappear in a random location on the screen, at the risk of self-destructing or appearing on top of an asteroid.
Each level starts with multiple large asteroids drifting across the screen. Objects wrap around screen edges; an asteroid that drifts off the top edge of the screen reappears at the bottom and continues moving in the same direction. As the player shoots asteroids, they break into smaller asteroids that move faster and are more difficult to hit. Smaller asteroids are also worth more points. Two flying saucers appear periodically on the screen; the "big saucer" shoots randomly and poorly, while the "small saucer" fires frequently at the ship. After reaching a score of 40,000, only the small saucer appears. As the player's score increases, the angle range of the shots from the small saucer diminishes until the saucer fires extremely accurately. Once the screen has been cleared of all asteroids and flying saucers, a new set of large asteroids appears, thus starting the next level. The game gets harder as the number of asteroids increases until after the score reaches a range between 40,000 and 60,000. The player starts with 3–5 lives upon game start and gains an extra life per 10,000 points. Play continues to the last ship lost, which ends the game. The machine "turns over" at 99,990 points, which is the maximum high score that can be achieved. |
Asteroids (video game) | Lurking exploit | Lurking exploit
In the original game design, saucers were supposed to begin shooting as soon as they appeared, but this was changed. Additionally, saucers can only aim at the player's ship on-screen; they are not capable of aiming across a screen boundary. These behaviors allow a "lurking" strategy, in which the player stays near the edge of the screen opposite the saucer. By keeping just one or two rocks in play, a player can shoot across the boundary and destroy saucers to accumulate points indefinitely with little risk of being destroyed. Arcade operators began to complain about losing revenue due to this exploit. In response, Atari issued a patched EPROM and, due to the impact of this exploit, Atari (and other companies) changed their development and testing policies to try to prevent future games from having such exploits. |
Asteroids (video game) | Development | Development
Asteroids was conceived by Lyle Rains and programmed by Ed Logg with collaborations from other Atari staff. Logg was impressed with the Atari Video Computer System (later called the Atari 2600), and he joined Atari's coin-op division to work on Dirt Bike, which was never released due to an unsuccessful field test. Paul Mancuso joined the development team as Asteroids technician and engineer Wendi Allen contributed to the hardware. During a meeting in April 1979, Rains discussed Planet Grab, a multiplayer arcade game later renamed to Cosmos. The unfinished game featured a giant, indestructible asteroid. Logg did play Cosmos and remembered shooting the indestructible asteroid to no effect. So Rains asked Logg: "Well, why don't we have a game where you shoot the rocks and blow them up?" In response, Logg described a similar concept where the player selectively shoots at rocks that break into smaller pieces. Thus combining the two-dimensional approach of Space War with Space Invaders addictive gameplay of "completion" and "eliminate all threats". Both agreed on the concept. |
Asteroids (video game) | Hardware | Hardware
Asteroids was implemented on hardware developed by Allen and is a vector game, in which the graphics are composed of lines drawn on a vector monitor. Rains initially wanted the game done in raster graphics, but Logg, experienced in vector graphics, suggested an XY monitor because the high image quality would permit precise aiming. The hardware is chiefly a MOS 6502 executing the game program, and QuadraScan, a high-resolution vector graphics processor developed by Atari and referred to as an "XY display system" and the "Digital Vector Generator (DVG)".Asteroids Flyer, 1979, Atari, Inc.
The original design concepts for QuadraScan came out of Cyan Engineering, Atari's off-campus research lab in Grass Valley, California, in 1978. Cyan gave it to Wendi Allen, who finished the design and first used it for Lunar Lander. Logg received Allen's modified board with five buttons, 13 sound effects, and additional RAM, and he used it to develop Asteroids. The size of the board was 4 by 4 inches, and it was "linked up" to a monitor. |
Asteroids (video game) | Implementation | Implementation
Logg modeled the player's ship, the five-button control scheme, and the game physics after Spacewar!, which he had played as a student at the University of California, Berkeley, but made several changes to improve playability. The ship was programmed into the hardware and rendered by the monitor, and it was configured to move with thrust and inertia. The hyperspace button was not placed near Logg's right thumb, which he was dissatisfied with, as he had a problem "tak[ing] his hand off the thrust button". Drawings of asteroids in various shapes were incorporated into the game. Logg copied the idea of a high score table with initials from Exidy's Star Fire.
The two saucers were formulated to be different from each other. A steadily decreasing timer shortens intervals between saucer attacks to keep the player from not shooting asteroids and saucers. A "heartbeat" soundtrack quickens as the game progresses. The game does not have a sound chip. Allen created a hardware circuit for 13 sound effects by hand which was wired onto the board.
A prototype of Asteroids was well received by several Atari staff and engineers, who "wander[ed] between labs, passing comment and stopping to play as they went". Logg was often asked when he would be leaving by employees eager to play the prototype, so he created a second prototype for staff to play. Atari tested the game in arcades in Sacramento, California, and also observed players during focus group sessions at Atari. Players used to Spacewar! struggled to maintain grip on the thrust button and requested a joystick; players accustomed to Space Invaders noted they get no break in the game. Logg and other engineers observed proceedings and documented comments in four pages. |
Asteroids (video game) | Quirks | Quirks
Asteroids slows down as the player gains 50–100 lives, because there is no limit to the number of lives displayed. The game's code continues trying to draw them even if they fall outside the boundaries of the screen. After more than 250 lives are collected, the game slows down enough that the watchdog timer thinks it has crashed and reboots the hardware.
There is limit of 26 asteroids. If there are already that many, shooting a large asteroid turns it into a single medium one, rather than two as per normal. Similarly, a medium asteroid turns into a single small one instead of splitting. |
Asteroids (video game) | Ports | Ports
Asteroids was released for the Atari VCS (later renamed Atari 2600) and Atari 8-bit computers in 1981. Programmers Brad Stewart and Bob Smith were unable to fit the Atari VCS port into a 4 KB cartridge. It became the first game for the console to use bank switching, a technique that increases ROM size from 4 KB to 8 KB. A port for the Atari 5200, identical to the Atari 8-bit version, was in development in 1982, but was not published.
An Atari 7800 version was published in 1986 with the official launch of the console. It includes cooperative play and colorful bitmapped graphics. |
Asteroids (video game) | Reception | Reception
Asteroids was immediately successful upon release. It displaced Space Invaders by popularity in the United States and became Atari's best selling arcade game of all time, with over 70,000 units sold. Atari earned an estimated $150 million in sales from the game, and arcade operators earned a further $500 million from coin drops. Atari had been in the process of manufacturing another vector game, Lunar Lander, but demand for Asteroids was so high "that several hundred Asteroids games were shipped in Lunar Lander cabinets". Asteroids was so popular that some video arcade operators had to install large boxes to hold the number of coins spent by players, and Atari assembly line workers that ignored other games they built played finished Asteroids machines awaiting shipping. It replaced Space Invaders at the top of the US RePlay amusement arcade charts in April 1980, though Space Invaders remained the top game at street locations. Asteroids went on to become the highest-grossing arcade video game of 1980 in the United States, dethroning Space Invaders. It shipped 70,000 arcade units worldwide in 1980, including over 60,000 sold in the United States that year, and grossed about worldwide ( adjusted for inflation) by 1980. The game remained at the top of the US RePlay charts through March 1981. The game did not perform as well overseas in Europe and Asia. It sold 30,000 arcade units overseas, for a total of 100,000 arcade units sold worldwide. Atari manufactured 76,312 units from its US and Ireland plants, including 21,394 Asteroids Deluxe units. It was a commercial failure in Japan when it released there in 1980, partly due to its complex controls and partly due to the Japanese market beginning to lose interest in space shoot 'em ups at the time.
Asteroids received positive reviews from video game critics and has been regarded as Logg's magnum opus. Richard A. Edwards reviewed the 1981 Asteroids home cartridge in The Space Gamer No. 46. Edwards commented that "this home cartridge is a virtual duplicate of the ever-popular Atari arcade game. [...] If blasting asteroids is the thing you want to do then this is the game, but at this price I can't wholeheartedly recommend it". Video Games Player magazine reviewed the Atari VCS version, rating the graphics and sound a B, while giving the game an overall B+ rating. Electronic Fun with Computers & Games magazine gave the Atari VCS version an A rating.
William Cassidy, writing for GameSpy's "Classic Gaming", noticed its innovations, including being one of the first video games to track initials and allow players to enter their initials for appearing in the top 10 high scores, and commented that "the vector graphics fit the futuristic outer space theme very well". In 1995, Flux magazine ranked the arcade version 11th on their "Top 100 Video Games". In 1996, Next Generation listed it as number 39 on their "Top 100 Games of All Time", particularly lauding the control dynamics which require "the constant juggling of speed, positioning, and direction". In 1999, Next Generation listed Asteroids as number 29 on their "Top 50 Games of All Time", commenting that "Asteroids was a classic the day it was released, and it has never lost any of its appeal". Asteroids was ranked fourth on Retro Gamers list of "Top 25 Arcade Games"; the Retro Gamer staff cited its simplicity and the lack of a proper ending as allowances of revisiting the game. In 2012, Asteroids was listed on Time All-Time 100 greatest video games list. Entertainment Weekly named Asteroids one of the top ten games for the Atari 2600 in 2013. It was added to the Museum of Modern Art's collection of video games. In 2021, The Guardian listed Asteroids as the second greatest video game of the 1970s, just below Galaxian (1979). By contrast, in March 1983 the Atari 8-bit port of Asteroids won sixth place in Softlines Dog of the Year awards "for badness in computer games", Atari division, based on reader submissions.
Usage of the names of Saturday Night Live characters "Mr. Bill" and "Sluggo" to refer to the saucers in an Esquire article about the game led to Logg receiving a cease and desist letter from a lawyer with the "Mr. Bill Trademark". |
Asteroids (video game) | Legacy | Legacy |
Asteroids (video game) | Arcade sequels | Arcade sequels
Released in 1981, Asteroids Deluxe was the first sequel to Asteroids. Dave Shepperd edited the code and made enhancements to the game without Logg's involvement. The onscreen objects are tinted blue, and hyperspace is replaced by a shield that depletes when used. The asteroids rotate, and new "killer satellite" enemies break into smaller ships that home in on the player's position. The arcade machine's monitor displays vector graphics overlaying a holographic backdrop. The game is more difficult than the original and enables saucers to shoot across the screen boundary, eliminating the lurking strategy for high scores in the original.
Space Duel, released in arcades in 1982, replaces the rocks with colorful geometric shapes and adds cooperative two-player gameplay.
1987's Blasteroids includes power-ups, ship morphing, branching levels, bosses, and the ability to dock ships in multiplayer for added firepower. Blasteroids uses raster graphics instead of vectors. |
Asteroids (video game) | Re-releases | Re-releases
The game is half of the Atari Lynx pairing Super Asteroids & Missile Command and included in the 1993 Microsoft Arcade compilation.
Activision published an enhanced version of Asteroids for the PlayStation (1998), Nintendo 64 (1999), Microsoft Windows (1998), Game Boy Color (1999), and Mac (2000). The Atari Flashback series of dedicated video game consoles have included both the 2600 and the arcade versions of Asteroids.
Asteroids Hyper 64 made the ship and asteroids 3D, and added new weapons and a multiplayer mode. It was developed by Syrox Developments and published by Crave Entertainment for the Nintendo 64.
A technical demo of Asteroids was developed by iThink for the Atari Jaguar but was never released. Unofficially referred to as Asteroids 2000, it was demonstrated at E-JagFest 2000. An updated version of the game was announced in 2018 for the Intellivision Amico.
Different versions of Asteroids were included in several Atari games compilations, such as Atari Anniversary Edition (2001) for the Dreamcast, PlayStation, and Microsoft Windows, Atari Anthology (2003) for both Xbox and PlayStation 2, Atari Greatest Hits Volume 1 (2010) for the Nintendo DS, Atari Collection 1 and 2 in 2020 for the Evercade, and Atari 50 (2022) for the Atari VCS, Nintendo Switch, PlayStation 4, PlayStation 5, Windows, Xbox One, and Xbox Series X/S.
Released in November 2007, the Xbox Live Arcade port of Asteroids has revamped HD graphics along with an added intense "throttle monkey" mode. The arcade and 2600 versions were made available through Microsofts Game Room service in 2010. Glu Mobile released an enhanced mobile phone port.
In 2005 Asteroids was released for the Game Boy Advance with Pong and Yars' Revenge also being included on the same package.
A remake, Asteroids: Recharged, was released in December 2021 for the Nintendo Switch, PlayStation 4, PlayStation 5, Windows, Xbox One, and Xbox Series X/S, developed by Adamvision Studios and SneakyBox and published by Atari.
In November 2024, Alan-1 Inc. released an official coin-op arcade version of Asteroids Recharged. The game won the first place in Best New Product of the category Games and Devices of the IAAPA 2024 Brass Ring Awards. |
Asteroids (video game) | Clones | Clones
Quality Software's Asteroids in Space (1980) was one of the best selling games for the Apple II and voted one of the most popular software titles of 1978–80 by Softalk magazine. In December 1981, Byte reviewed eight Asteroids clones for home computers. Three clones for the Apple II were reviewed together in the 1982 Creative Computing Software Buyers Guide: The Asteroid Field, Asteron, and Apple-Oids. In the last of these, the asteroids are in the shape of apples. Two independent clones, Asteroid for the Apple II and Fasteroids for TRS-80, were renamed to Planetoids and sold by Adventure International. Others clones include Acornsoft's Meteors, Moons of Jupiter for the VIC-20, MineStorm for the Vectrex, and Quicksilva's Meteor Storm for the ZX Spectrum which uses speech synthesis. A poorly implemented Asteroids clone for the VIC-20, published by Bug-Byte, motivated Jeff Minter to found Llamasoft.
The Intellivision game Meteor! was cancelled to avoid a lawsuit for being too similar to Asteroids and was reworked as Astrosmash. The game borrows elements from Asteroids and Space Invaders. |
Asteroids (video game) | Proposed film adaptation | Proposed film adaptation
In July 2009, Universal Pictures offered Roland Emmerich the option to direct the film adaptation of Asteroids, with Matt Lopez writing the script and Lorenzo di Bonaventura producing the film adaptation. Lopez and di Bonaventura were still attached to write and produce the film adaptation, respectively, but Emmerich passed on directing, while Evan Spiliotopoulos and F. Scott Frazier were hired to rewrite the screenplay. |
Asteroids (video game) | In other media | In other media
The game has made cameo appearances in a number of films and music videos. An Asteroids machine appears in the music video for 38 Special's song Caught Up in You, and one is also briefly seen in the movie Pee-Wee's Big Adventure. |
Asteroids (video game) | World records | World records
On February 6, 1982, Leo Daniels of Carolina Beach, North Carolina, set a world record score of 40,101,910 points. On November 13 of the same year, 15-year-old Scott Safran of Cherry Hill, New Jersey, set a new record at 41,336,440 points. In 1998, to congratulate Safran on his accomplishment, the Twin Galaxies Intergalactic Scoreboard searched for him for four years until 2002, when it was discovered that he had died in an accident in 1989. In a ceremony in Philadelphia on April 27, 2002, Walter Day of Twin Galaxies presented an award to the surviving members of Safran's family, commemorating his achievement. On April 5, 2010, John McAllister broke Safran's record with a high score of 41,838,740 in a 58-hour Internet livestream. |
Asteroids (video game) | References | References |
Asteroids (video game) | External links | External links
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Asteroids (video game) | Table of Content | Short description, Gameplay, Lurking exploit, Development, Hardware, Implementation, Quirks, Ports, Reception, Legacy, Arcade sequels, Re-releases, Clones, Proposed film adaptation, In other media, World records, References, External links |
Asparagales | Short description | Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,000 species, with members as varied as asparagus, orchids, yuccas, irises, onions, garlic, leeks, and other Alliums, daffodils, snowdrops, amaryllis, agaves, butcher's broom, Agapanthus, Solomon's seal, hyacinths, bluebells, spider plants, grasstrees, aloe, freesias, gladioli, crocuses, and saffron.
Most species of Asparagales are herbaceous perennials, although some are climbers and some are trees or shrubs. The order also contains many geophytes (bulbs, corms, and various kinds of tuber). The leaves of almost all species form a tight rosette, either at the base of the plant or at the end of the stem, but occasionally along the stem. The flowers are not particularly distinctive, being 'lily type', with six tepals and up to six stamina. One of the defining characteristics (synapomorphies) of the order is the presence of phytomelanin, a black pigment present in the seed coat, creating a dark crust. Phytomelanin is found in most families of the Asparagales (although not in Orchidaceae, thought to be the sister-group of the rest of the order).
The order Asparagales takes its name from the type family Asparagaceae and has only recently been recognized in classification systems. The order is clearly circumscribed on the basis of molecular phylogenetics, but it is difficult to define morphologically since its members are structurally diverse. The order was first put forward by Huber in 1977 and later taken up in the Dahlgren system of 1985 and then the Angiosperm Phylogeny Group systems. Before this, many of its families were assigned to the old order Liliales, which was redistributed over three orders, Liliales, Asparagales, and Dioscoreales, based on molecular phylogenetics. The boundaries of the Asparagales and of its families have undergone a series of changes in recent years; future research may lead to further changes and ultimately greater stability.
The order is thought to have first diverged from other related monocots some 120–130 million years ago (early in the Cretaceous period), although given the difficulty in classifying the families involved, estimates are likely to be uncertain.
From an economic point of view, the order Asparagales is second in importance within the monocots only to the order Poales (which includes grasses and cereals). Species are used as food and flavourings (e.g. onion, garlic, leek, asparagus, vanilla, saffron), in medicinal or cosmetic applications (Aloe), as cut flowers (e.g. freesia, gladiolus, iris, orchids), and as garden ornamentals (e.g. day lilies, lily of the valley, Agapanthus). |
Asparagales | Description | Description
thumb | Seeds of Hippeastrum with dark phytomelan-containing coat
thumb | Tree-like habit created by secondary thickening in Beaucarnea recurvata
Although most species in the order are herbaceous, some no more than 15 cm high, there are a number of climbers (e.g., some species of Asparagus), as well as several genera forming trees (e.g. Agave, Cordyline, Yucca, Dracaena, Aloidendron ), which can exceed 10 m in height. Succulent genera occur in several families (e.g. Aloe).
Almost all species have a tight cluster of leaves (a rosette), either at the base of the plant or at the end of a more-or-less woody stem as with Yucca. In some cases, the leaves are produced along the stem. The flowers are in the main not particularly distinctive, being of a general 'lily type', with six tepals, either free or fused from the base and up to six stamina. They are frequently clustered at the end of the plant stem.
The Asparagales are generally distinguished from the Liliales by the lack of markings on the tepals, the presence of septal nectaries in the ovaries, rather than the bases of the tepals or stamen filaments, and the presence of secondary growth. They are generally geophytes, but with linear leaves, and a lack of fine reticular venation.
The seeds characteristically have the external epidermis either obliterated (in most species bearing fleshy fruit), or if present, have a layer of black carbonaceous phytomelanin in species with dry fruits (nuts). The inner part of the seed coat is generally collapsed, in contrast to Liliales whose seeds have a well developed outer epidermis, lack phytomelanin, and usually display a cellular inner layer.
The orders which have been separated from the old Liliales are difficult to characterize. No single morphological character appears to be diagnostic of the order Asparagales.
The flowers of Asparagales are of a general type among the lilioid monocots. Compared to Liliales, they usually have plain tepals without markings in the form of dots. If nectaries are present, they are in the septa of the ovaries rather than at the base of the tepals or stamens.
Those species which have relatively large dry seeds have a dark, crust-like (crustose) outer layer containing the pigment phytomelan. However, some species with hairy seeds (e.g. Eriospermum, family Asparagaceae s.l.), berries (e.g. Maianthemum, family Asparagaceae s.l.), or highly reduced seeds (e.g. orchids) lack this dark pigment in their seed coats. Phytomelan is not unique to Asparagales (i.e. it is not a synapomorphy) but it is common within the order and rare outside it. The inner portion of the seed coat is usually completely collapsed. In contrast, the morphologically similar seeds of Liliales have no phytomelan, and usually retain a cellular structure in the inner portion of the seed coat.
Most monocots are unable to thicken their stems once they have formed, since they lack the cylindrical meristem present in other angiosperm groups. Asparagales have a method of secondary thickening which is otherwise only found in Dioscorea (in the monocot order Disoscoreales). In a process called 'anomalous secondary growth', they are able to create new vascular bundles around which thickening growth occurs. Agave, Yucca, Aloidendron, Dracaena, Nolina and Cordyline can become massive trees, albeit not of the height of the tallest dicots, and with less branching. Other genera in the order, such as Lomandra and Aphyllanthes, have the same type of secondary growth but confined to their underground stems.
Microsporogenesis (part of pollen formation) distinguishes some members of Asparagales from Liliales. Microsporogenesis involves a cell dividing twice (meiotically) to form four daughter cells. There are two kinds of microsporogenesis: successive and simultaneous (although intermediates exist). In successive microsporogenesis, walls are laid down separating the daughter cells after each division. In simultaneous microsporogenesis, there is no wall formation until all four cell nuclei are present. Liliales all have successive microsporogenesis, which is thought to be the primitive condition in monocots. It seems that when the Asparagales first diverged they developed simultaneous microsporogenesis, which the 'lower' Asparagales families retain. However, the 'core' Asparagales (see Phylogenetics ) have reverted to successive microsporogenesis.
The Asparagales appear to be unified by a mutation affecting their telomeres (a region of repetitive DNA at the end of a chromosome). The typical 'Arabidopsis-type' sequence of bases has been fully or partially replaced by other sequences, with the 'human-type' predominating.
Other apomorphic characters of the order according to Stevens are: the presence of chelidonic acid, anthers longer than wide, tapetal cells bi- to tetra-nuclear, tegmen not persistent, endosperm helobial, and loss of mitochondrial gene sdh3.
According to telomere sequence, at least two evolutionary switch-points happened within the order. The basal sequence is formed by TTTAGGG like in the majority of higher plants. Basal motif was changed to vertebrate-like TTAGGG and finally, the most divergent motif CTCGGTTATGGG appears in Allium. |
Asparagales | Taxonomy | Taxonomy
As circumscribed within the Angiosperm Phylogeny Group system Asparagales is the largest order within the monocotyledons, with 14 families, 1,122 genera and about 25,000–42,000 species, thus accounting for about 50% of all monocots and 10–15% of the flowering plants (angiosperms). The attribution of botanical authority for the name Asparagales belongs to Johann Heinrich Friedrich Link (1767–1851) who coined the word 'Asparaginae' in 1829 for a higher order taxon that included Asparagus although Adanson and Jussieau had also done so earlier (see History). Earlier circumscriptions of Asparagales attributed the name to Bromhead (1838), who had been the first to use the term 'Asparagales'. |
Asparagales | History | History |
Asparagales | Pre-Darwinian | Pre-Darwinian
The type genus, Asparagus, from which the name of the order is derived, was described by Carl Linnaeus in 1753, with ten species. He placed Asparagus within the Hexandria Monogynia (six stamens, one carpel) in his sexual classification in the Species Plantarum. The majority of taxa now considered to constitute Asparagales have historically been placed within the very large and diverse family, Liliaceae. The family Liliaceae was first described by Michel Adanson in 1763, and in his taxonomic scheme he created eight sections within it, including the Asparagi with Asparagus and three other genera. The system of organising genera into families is generally credited to Antoine Laurent de Jussieu who formally described both the Liliaceae and the type family of Asparagales, the Asparagaceae, as Lilia and Asparagi, respectively, in 1789. Jussieu established the hierarchical system of taxonomy (phylogeny), placing Asparagus and related genera within a division of Monocotyledons, a class (III) of Stamina Perigynia and 'order' Asparagi, divided into three subfamilies. The use of the term Ordo (order) at that time was closer to what we now understand as Family, rather than Order. In creating his scheme he used a modified form of Linnaeus' sexual classification but using the respective topography of stamens to carpels rather than just their numbers. While De Jussieu's Stamina Perigynia also included a number of 'orders' that would eventually form families within the Asparagales such as the Asphodeli (Asphodelaceae), Narcissi (Amaryllidaceae) and Irides (Iridaceae), the remainder are now allocated to other orders. Jussieu's Asparagi soon came to be referred to as Asparagacées in the French literature (Latin: Asparagaceae). Meanwhile, the 'Narcissi' had been renamed as the 'Amaryllidées' (Amaryllideae) in 1805, by Jean Henri Jaume Saint-Hilaire, using Amaryllis as the type species rather than Narcissus, and thus has the authority attribution for Amaryllidaceae. In 1810, Brown proposed that a subgroup of Liliaceae be distinguished on the basis of the position of the ovaries and be referred to as Amaryllideae and in 1813 de Candolle described Liliacées Juss. and Amaryllidées Brown as two quite separate families.
The literature on the organisation of genera into families and higher ranks became available in the English language with Samuel Frederick Gray's A natural arrangement of British plants (1821). Gray used a combination of Linnaeus' sexual classification and Jussieu's natural classification to group together a number of families having in common six equal stamens, a single style and a perianth that was simple and petaloid, but did not use formal names for these higher ranks. Within the grouping he separated families by the characteristics of their fruit and seed. He treated groups of genera with these characteristics as separate families, such as Amaryllideae, Liliaceae, Asphodeleae and Asparageae.
thumb|Amaryllidaceae: Narcisseae – Pancratium maritimum L. John Lindley, Vegetable Kingdom 1846
The circumscription of Asparagales has been a source of difficulty for many botanists from the time of John Lindley (1846), the other important British taxonomist of the early nineteenth century. In his first taxonomic work, An Introduction to the Natural System of Botany (1830) he partly followed Jussieu by describing a subclass he called Endogenae, or Monocotyledonous Plants (preserving de Candolle's Endogenæ phanerogamæ) divided into two tribes, the Petaloidea and Glumaceae. He divided the former, often referred to as petaloid monocots, into 32 orders, including the Liliaceae (defined narrowly), but also most of the families considered to make up the Asparagales today, including the Amaryllideae.
By 1846, in his final scheme Lindley had greatly expanded and refined the treatment of the monocots, introducing both an intermediate ranking (Alliances) and tribes within orders (i.e. families). Lindley placed the Liliaceae within the Liliales, but saw it as a paraphyletic ("catch-all") family, being all Liliales not included in the other orders, but hoped that the future would reveal some characteristic that would group them better. The order Liliales was very large and included almost all monocotyledons with colourful tepals and without starch in their endosperm (the lilioid monocots). The Liliales was difficult to divide into families because morphological characters were not present in patterns that clearly demarcated groups. This kept the Liliaceae separate from the Amaryllidaceae (Narcissales). Of these, Liliaceae was divided into eleven tribes (with 133 genera) and Amaryllidaceae into four tribes (with 68 genera), yet both contained many genera that would eventually segregate to each other's contemporary orders (Liliales and Asparagales respectively). The Liliaceae would be reduced to a small 'core' represented by the tribe Tulipae, while large groups such Scilleae and Asparagae would become part of Asparagales either as part of the Amaryllidaceae or as separate families. While of the Amaryllidaceae, the Agaveae would be part of Asparagaceae but the Alstroemeriae would become a family within the Liliales.
The number of known genera (and species) continued to grow and by the time of the next major British classification, that of the Bentham & Hooker system in 1883 (published in Latin) several of Lindley's other families had been absorbed into the Liliaceae. They used the term 'series' to indicate suprafamilial rank, with seven series of monocotyledons (including Glumaceae), but did not use Lindley's terms for these. However, they did place the Liliaceous and Amaryllidaceous genera into separate series. The Liliaceae were placed in series Coronariae, while the Amaryllideae were placed in series Epigynae. The Liliaceae now consisted of twenty tribes (including Tulipeae, Scilleae and Asparageae), and the Amaryllideae of five (including Agaveae and Alstroemerieae). An important addition to the treatment of the Liliaceae was the recognition of the Allieae as a distinct tribe that would eventually find its way to the Asparagales as the subfamily Allioideae of the Amaryllidaceae. |
Asparagales | Post-Darwinian | Post-Darwinian
The appearance of Charles Darwin's Origin of Species in 1859 changed the way that taxonomists considered plant classification, incorporating evolutionary information into their schemata. The Darwinian approach led to the concept of phylogeny (tree-like structure) in assembling classification systems, starting with Eichler. Eichler, having established a hierarchical system in which the flowering plants (angiosperms) were divided into monocotyledons and dicotyledons, further divided into former into seven orders. Within the Liliiflorae were seven families, including Liliaceae and Amaryllidaceae. Liliaceae included Allium and Ornithogalum (modern Allioideae) and Asparagus.
Engler, in his system developed Eichler's ideas into a much more elaborate scheme which he treated in a number of works including Die Natürlichen Pflanzenfamilien (Engler and Prantl 1888) and Syllabus der Pflanzenfamilien (1892–1924). In his treatment of Liliiflorae the Liliineae were a suborder which included both families Liliaceae and Amaryllidaceae. The Liliaceae had eight subfamilies and the Amaryllidaceae four. In this rearrangement of Liliaceae, with fewer subdivisions, the core Liliales were represented as subfamily Lilioideae (with Tulipae and Scilleae as tribes), the Asparagae were represented as Asparagoideae and the Allioideae was preserved, representing the alliaceous genera. Allieae, Agapantheae and Gilliesieae were the three tribes within this subfamily. In the Amaryllidaceae, there was little change from the Bentham & Hooker. A similar approach was adopted by Wettstein. |
Asparagales | Twentieth century | Twentieth century
thumb|Longitudinal section of Narcissus poeticus, R Wettstein Handbuch der Systematischen Botanik 1901–1924In the twentieth century the Wettstein system (1901–1935) placed many of the taxa in an order called 'Liliiflorae'. Next Johannes Paulus Lotsy (1911) proposed dividing the Liliiflorae into a number of smaller families including Asparagaceae. Then Herbert Huber (1969, 1977), following Lotsy's example, proposed that the Liliiflorae be split into four groups including the 'Asparagoid' Liliiflorae.
The widely used Cronquist system (1968–1988) used the very broadly defined order Liliales.
These various proposals to separate small groups of genera into more homogeneous families made little impact till that of Dahlgren (1985) incorporating new information including synapomorphy. Dahlgren developed Huber's ideas further and popularised them, with a major deconstruction of existing families into smaller units. They created a new order, calling it Asparagales. This was one of five orders within the superorder Liliiflorae. Where Cronquist saw one family, Dahlgren saw forty distributed over three orders (predominantly Liliales and Asparagales). Over the 1980s, in the context of a more general review of the classification of angiosperms, the Liliaceae were subjected to more intense scrutiny. By the end of that decade, the Royal Botanic Gardens at Kew, the British Museum of Natural History and the Edinburgh Botanical Gardens formed a committee to examine the possibility of separating the family at least for the organization of their herbaria. That committee finally recommended that 24 new families be created in the place of the original broad Liliaceae, largely by elevating subfamilies to the rank of separate families. |
Asparagales | Phylogenetics | Phylogenetics
The order Asparagales as currently circumscribed has only recently been recognized in classification systems, through the advent of phylogenetics. The 1990s saw considerable progress in plant phylogeny and phylogenetic theory, enabling a phylogenetic tree to be constructed for all of the flowering plants. The establishment of major new clades necessitated a departure from the older but widely used classifications such as Cronquist and Thorne based largely on morphology rather than genetic data. This complicated the discussion about plant evolution and necessitated a major restructuring. rbcL gene sequencing and cladistic analysis of monocots had redefined the Liliales in 1995.. from four morphological orders sensu Dahlgren. The largest clade representing the Liliaceae, all previously included in Liliales, but including both the Calochortaceae and Liliaceae sensu Tamura. This redefined family, that became referred to as core Liliales, but corresponded to the emerging circumscription of the Angiosperm Phylogeny Group (1998). |
Asparagales | Phylogeny and APG system | Phylogeny and APG system
The 2009 revision of the Angiosperm Phylogeny Group system, APG III, places the order in the clade monocots.
From the Dahlgren system of 1985 onwards, studies based mainly on morphology had identified the Asparagales as a distinct group, but had also included groups now located in Liliales, Pandanales and Zingiberales. Research in the 21st century has supported the monophyly of Asparagales, based on morphology, 18S rDNA, and other DNA sequences, although some phylogenetic reconstructions based on molecular data have suggested that Asparagales may be paraphyletic, with Orchidaceae separated from the rest. Within the monocots, Asparagales is the sister group of the commelinid clade.
This cladogram shows the placement of Asparagales within the orders of Lilianae sensu Chase & Reveal (monocots) based on molecular phylogenetic evidence. The lilioid monocot orders are bracketed, namely Petrosaviales, Dioscoreales, Pandanales, Liliales and Asparagales. These constitute a paraphyletic assemblage, that is groups with a common ancestor that do not include all direct descendants (in this case commelinids as the sister group to Asparagales); to form a clade, all the groups joined by thick lines would need to be included. While Acorales and Alismatales have been collectively referred to as "alismatid monocots" (basal or early branching monocots), the remaining clades (lilioid and commelinid monocots) have been referred to as the "core monocots". The relationship between the orders (with the exception of the two sister orders) is pectinate, that is diverging in succession from the line that leads to the commelinids. Numbers indicate crown group (most recent common ancestor of the sampled species of the clade of interest) divergence times in mya (million years ago). |
Asparagales | Subdivision | Subdivision
A phylogenetic tree for the Asparagales, generally to family level, but including groups which were recently and widely treated as families but which are now reduced to subfamily rank, is shown below.
The tree shown above can be divided into a basal paraphyletic group, the 'lower Asparagales (asparagoids)', from Orchidaceae to Asphodelaceae, and a well-supported monophyletic group of 'core Asparagales' (higher asparagoids), comprising the two largest families, Amaryllidaceae sensu lato and Asparagaceae sensu lato.
Two differences between these two groups (although with exceptions) are: the mode of microsporogenesis and the position of the ovary. The 'lower Asparagales' typically have simultaneous microsporogenesis (i.e. cell walls develop only after both meiotic divisions), which appears to be an apomorphy within the monocots, whereas the 'core Asparagales' have reverted to successive microsporogenesis (i.e. cell walls develop after each division). The 'lower Asparagales' typically have an inferior ovary, whereas the 'core Asparagales' have reverted to a superior ovary. A 2002 morphological study by Rudall treated possessing an inferior ovary as a synapomorphy of the Asparagales, stating that reversions to a superior ovary in the 'core Asparagales' could be associated with the presence of nectaries below the ovaries. However, Stevens notes that superior ovaries are distributed among the 'lower Asparagales' in such a way that it is not clear where to place the evolution of different ovary morphologies. The position of the ovary seems a much more flexible character (here and in other angiosperms) than previously thought. |
Asparagales | Changes to family structure in APG III | Changes to family structure in APG III
The APG III system when it was published in 2009, greatly expanded the families Xanthorrhoeaceae, Amaryllidaceae, and Asparagaceae. Thirteen of the families of the earlier APG II system were thereby reduced to subfamilies within these three families. The expanded Xanthorrhoeaceae is now called "Asphodelaceae". The APG II families (left) and their equivalent APG III subfamilies (right) are as follows:
Asphodelaceae
Hemerocallidaceae=Hemerocallidoideae
Xanthorrhoeaceae=Xanthorrhoeoideae
Asphodelaceae=AsphodeloideaeAmaryllidaceae
Agapanthaceae=Agapanthoideae
Alliaceae =Allioideae
Amaryllidaceae=AmaryllidoideaeAsparagaceae
Aphyllanthaceae = Aphyllanthoideae
Laxmanniaceae = Lomandroideae
Asparagaceae = Asparagoideae
Ruscaceae = Nolinoideae
Agavaceae = Agavoideae
Themidaceae = Brodiaeoideae
Hyacinthaceae = Scilloideae |
Asparagales | Structure of Asparagales | Structure of Asparagales |
Asparagales | Orchid clade | Orchid clade
Orchidaceae is possibly the largest family of all angiosperms (only Asteraceae might – or might not – be more speciose) and hence by far the largest in the order. The Dahlgren system recognized three families of orchids, but DNA sequence analysis later showed that these families are polyphyletic and so should be combined. Several studies suggest (with high bootstrap support) that Orchidaceae is the sister of the rest of the Asparagales. Other studies have placed the orchids differently in the phylogenetic tree, generally among the Boryaceae-Hypoxidaceae clade. The position of Orchidaceae shown above seems the best current hypothesis, but cannot be taken as confirmed.
Orchids have simultaneous microsporogenesis and inferior ovaries, two characters that are typical of the 'lower Asparagales'. However, their nectaries are rarely in the septa of the ovaries, and most orchids have dust-like seeds, atypical of the rest of the order. (Some members of Vanilloideae and Cypripedioideae have crustose seeds, probably associated with dispersal by birds and mammals that are attracted by fermenting fleshy fruit releasing fragrant compounds, e.g. vanilla.)
In terms of the number of species, Orchidaceae diversification is remarkable, with recent estimations suggesting that despite the old origin of the family dating back to the late cretaceous, modern orchid diversity originated mostly during the last 5 million years. However, although the other Asparagales may be less rich in species, they are more variable morphologically, including tree-like forms. |
Asparagales | Boryaceae to Hypoxidaceae | Boryaceae to Hypoxidaceae
The four families excluding Boryaceae form a well-supported clade in studies based on DNA sequence analysis. All four contain relatively few species, and it has been suggested that they be combined into one family under the name Hypoxidaceae sensu lato. The relationship between Boryaceae (which includes only two genera, Borya and Alania), and other Asparagales has remained unclear for a long time. The Boryaceae are mycorrhizal, but not in the same way as orchids. Morphological studies have suggested a close relationship between Boryaceae and Blandfordiaceae. There is relatively low support for the position of Boryaceae in the tree shown above. |
Asparagales | Ixioliriaceae to Xeronemataceae | Ixioliriaceae to Xeronemataceae
The relationship shown between Ixioliriaceae and Tecophilaeaceae is still unclear. Some studies have supported a clade of these two families, others have not. The position of Doryanthaceae has also varied, with support for the position shown above, but also support for other positions.
The clade from Iridaceae upwards appears to have stronger support. All have some genetic characteristics in common, having lost Arabidopsis-type telomeres. Iridaceae is distinctive among the Asparagales in the unique structure of the inflorescence (a rhipidium), the combination of an inferior ovary and three stamens, and the common occurrence of unifacial leaves whereas bifacial leaves are the norm in other Asparagales.
Members of the clade from Iridaceae upwards have infra-locular septal nectaries, which Rudall interpreted as a driver towards secondarily superior ovaries. |
Asparagales | Asphodelaceae + 'core Asparagales' | Asphodelaceae + 'core Asparagales'
The next node in the tree (Xanthorrhoeaceae sensu lato + the 'core Asparagales') has strong support. 'Anomalous' secondary thickening occurs among this clade, e.g. in Xanthorrhoea (family Asphodelaceae) and Dracaena (family Asparagaceae sensu lato), with species reaching tree-like proportions.
The 'core Asparagales', comprising Amaryllidaceae sensu lato and Asparagaceae sensu lato, are a strongly supported clade, as are clades for each of the families. Relationships within these broadly defined families appear less clear, particularly within the Asparagaceae sensu lato. Stevens notes that most of its subfamilies are difficult to recognize, and that significantly different divisions have been used in the past, so that the use of a broadly defined family to refer to the entire clade is justified. Thus the relationships among subfamilies shown above, based on APWeb , is somewhat uncertain. |
Asparagales | Evolution | Evolution
Several studies have attempted to date the evolution of the Asparagales, based on phylogenetic evidence. Earlier studies generally give younger dates than more recent studies, which have been preferred in the table below.
+ Approx. date inMillions of Years Ago Event 133-120 Origin of Asparagales, i.e. first divergence from other monocots 93 Split between Asphodelaceae and the 'core group' Asparagales 91–89 Origin of Alliodeae and Asparagoideae 47 Divergence of Agavoideae and Nolinoideae
A 2009 study suggests that the Asparagales have the highest diversification rate in the monocots, about the same as the order Poales, although in both orders the rate is little over half that of the eudicot order Lamiales, the clade with the highest rate. |
Asparagales | Comparison of family structures | Comparison of family structures
The taxonomic diversity of the monocotyledons is described in detail by Kubitzki. Up-to-date information on the Asparagales can be found on the Angiosperm Phylogeny Website.
The APG III system's family circumscriptions are being used as the basis of the Kew-hosted World Checklist of Selected Plant Families. With this circumscription, the order consists of 14 families (Dahlgren had 31) with approximately 1120 genera and 26000 species.
Order Asparagales Link
Family Amaryllidaceae J.St.-Hil. (including Agapanthaceae F.Voigt, Alliaceae Borkh.)The name 'Alliaceae' has also been used for the expanded family comprising the Alliaceae sensu stricto, Amaryllidaceae and Agapanthaceae (e.g. in the APG II system). 'Amaryllidaceae' is used as a conserved name in APG III.
Family Asparagaceae Juss. (including Agavaceae Dumort. [which includes Anemarrhenaceae, Anthericaceae, Behniaceae and Herreriaceae], Aphyllanthaceae Burnett, Hesperocallidaceae Traub, Hyacinthaceae Batsch ex Borkh., Laxmanniaceae Bubani, Ruscaceae M.Roem. [which includes Convallariaceae] and Themidaceae Salisb.)
Family Asteliaceae Dumort.
Family Blandfordiaceae R.Dahlgren & Clifford
Family Boryaceae M.W. Chase, Rudall & Conran
Family Doryanthaceae R.Dahlgren & Clifford
Family Hypoxidaceae R.Br.
Family Iridaceae Juss.
Family Ixioliriaceae Nakai
Family Lanariaceae R.Dahlgren & A.E.van Wyk
Family Orchidaceae Juss.
Family Tecophilaeaceae Leyb.
Family Xanthorrhoeaceae Dumort. (including Asphodelaceae Juss. and Hemerocallidaceae R.Br.), now Asphodelaceae Juss.
Family Xeronemataceae M.W.Chase, Rudall & M.F.Fay
The earlier 2003 version, APG II, allowed 'bracketed' families, i.e. families which could either be segregated from more comprehensive families or could be included in them. These are the families given under "including" in the list above. APG III does not allow bracketed families, requiring the use of the more comprehensive family; otherwise the circumscription of the Asparagales is unchanged. A separate paper accompanying the publication of the 2009 APG III system provided subfamilies to accommodate the families which were discontinued. The first APG system of 1998 contained some extra families, included in square brackets in the list above.
Two older systems which use the order Asparagales are the Dahlgren system and the Kubitzki system. The families included in the circumscriptions of the order in these two systems are shown in the first and second columns of the table below. The equivalent family in the modern APG III system (see below) is shown in the third column. Note that although these systems may use the same name for a family, the genera which it includes may be different, so the equivalence between systems is only approximate in some cases.
+ Families included in Asparagales in three systems which use this order Dahlgren system Kubitzki system APG III system – Agapanthaceae Amaryllidaceae: Agapanthoideae Agavaceae Asparagaceae: Agavoideae Alliaceae Amaryllidaceae: Allioideae Amaryllidaceae Amaryllidaceae: Amaryllidoideae – Anemarrhenaceae Asparagaceae: Agavoideae Anthericaceae Asparagaceae: Agavoideae Aphyllanthaceae Asparagaceae: Aphyllanthoideae Asparagaceae Asparagaceae: Asparagoideae Asphodelaceae Asphodelaceae: Asphodeloideae Asteliaceae Asteliaceae – Behniaceae Asparagaceae: Agavoideae Blandfordiaceae Blandfordiaceae – Boryaceae Boryaceae Calectasiaceae — Not in Asparagales (family Dasypogonaceae, unplaced as to order, clade commelinids) Convallariaceae Asparagaceae: Nolinoideae Cyanastraceae – Tecophilaeaceae Dasypogonaceae – Not in Asparagales (family Dasypogonaceae, unplaced as to order, clade commelinids) Doryanthaceae Doryanthaceae Dracaenaceae Asparagaceae: Nolinoideae Eriospermaceae Asparagaceae: Nolinoideae Hemerocallidaceae Asphodelaceae: Hemerocallidoideae Herreriaceae Asparagaceae: Agavoideae Hostaceae Asparagaceae: Agavoideae Hyacinthaceae Asparagaceae: Scilloideae Hypoxidaceae Hypoxidaceae – Iridaceae Iridaceae Ixioliriaceae Ixioliriaceae – Johnsoniaceae Asphodelaceae: Hemerocallidoideae Lanariaceae Lanariaceae Luzuriagaceae – Not in Asparagales (family Alstroemeriaceae, order Liliales) – Lomandraceae Asparagaceae: Lomandroideae Nolinaceae Asparagaceae: Nolinoideae – Orchidaceae Orchidaceae Philesiaceae – Not in Asparagales (family Philesiaceae, order Liliales) Phormiaceae – Asphodelaceae: Hemerocallidoideae Ruscaceae Asparagaceae: Nolinoideae Tecophilaeaceae Tecophilaeaceae – Themidaceae Asparagaceae: Brodiaeoideae Xanthorrhoeaceae Asphodelaceae: Xanthorrhoeoideae |
Asparagales | Uses | Uses
The Asparagales include many important crop plants and ornamental plants. Crops include Allium, Asparagus and Vanilla, while ornamentals include irises, hyacinths and orchids. |
Asparagales | See also | See also
Taxonomy of Liliaceae |
Asparagales | Notes | Notes |
Asparagales | References | References |
Asparagales | Bibliography | Bibliography |
Asparagales | Books | Books
contents
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Asparagales | Chapters | Chapters
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Asparagales | Articles | Articles
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Asparagales | APG | APG
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Asparagales | Historical sources | Historical sources
digital edition by the University and State Library Düsseldorf
1st ed. 1901–1908; 2nd ed. 1910–1911; 3rd ed. 1923–1924; 4th ed. 1933–1935
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Asparagales | Websites | Websites
: Families included in the checklist
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Asparagales | Reference materials | Reference materials
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Asparagales | External links | External links
Biodiversity Heritage Library
Category:Angiosperm orders
Category:Extant Late Cretaceous first appearances |
Asparagales | Table of Content | Short description, Description, Taxonomy, History, Pre-Darwinian, Post-Darwinian, Twentieth century, Phylogenetics, Phylogeny and APG system, Subdivision, Changes to family structure in APG III, Structure of Asparagales, Orchid clade, Boryaceae to Hypoxidaceae, Ixioliriaceae to Xeronemataceae, Asphodelaceae + 'core Asparagales', Evolution, Comparison of family structures, Uses, See also, Notes, References, Bibliography, Books, Chapters, Articles, APG, Historical sources, Websites, Reference materials, External links |
Alismatales | Short description | thumb|220px|Snake lily (Dracunculus vulgaris) of family Araceae in Crete, Greece.
thumb|220px|Ottelia alismoides from family Hydrocharitaceae in Hyderabad, India.
The Alismatales (alismatids) are an order of flowering plants including about 4,500 species. Plants assigned to this order are mostly tropical or aquatic. Some grow in fresh water, some in marine habitats. Perhaps the most important food crop in the order is the taro plant, Colocasia esculenta. |
Alismatales | Description | Description
The Alismatales comprise herbaceous flowering plants of often aquatic and marshy habitats, and the only monocots known to have green embryos other than the Amaryllidaceae. They also include the only marine angiosperms growing completely submerged, the seagrasses. The flowers are usually arranged in inflorescences, and the mature seeds lack endosperm.
Both marine and freshwater forms include those with staminate flowers that detach from the parent plant and float to the surface. There they can pollinate carpellate flowers floating on the surface via long pedicels. In others, pollination occurs underwater, where pollen may form elongated strands, increasing chance of success. Most aquatic species have a totally submerged juvenile phase, and flowers are either floating or emerge above the water's surface. Vegetation may be totally submersed, have floating leaves, or protrude from the water. Collectively, they are commonly known as "water plantain". |
Alismatales | Taxonomy | Taxonomy
The Alismatales contain about 165 genera in 13 families, with a cosmopolitan distribution. Phylogenetically, they are basal monocots, diverging early in evolution relative to the lilioid and commelinid monocot lineages. Together with the Acorales, the Alismatales are referred to informally as the alismatid monocots. |
Alismatales | Early systems | Early systems
The Cronquist system (1981) places the Alismatales in subclass Alismatidae, class Liliopsida [= monocotyledons] and includes only three families as shown:
Alismataceae
Butomaceae
Limnocharitaceae
Cronquist's subclass Alismatidae conformed fairly closely to the order Alismatales as defined by APG, minus the Araceae.
The Dahlgren system places the Alismatales in the superorder Alismatanae in the subclass Liliidae [= monocotyledons] in the class Magnoliopsida [= angiosperms] with the following families included:
Alismataceae
Aponogetonaceae
Butomaceae
Hydrocharitaceae
Limnocharitaceae
In Tahktajan's classification (1997), the order Alismatales contains only the Alismataceae and Limnocharitaceae, making it equivalent to the Alismataceae as revised in APG-III. Other families included in the Alismatates as currently defined are here distributed among 10 additional orders, all of which are assigned, with the following exception, to the Subclass Alismatidae. Araceae in Tahktajan 1997 is assigned to the Arales and placed in the Subclass Aridae; Tofieldiaceae to the Melanthiales and placed in the Liliidae. |
Alismatales | Angiosperm Phylogeny Group | Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group system (APG) of 1998 and APG II (2003) assigned the Alismatales to the monocots, which may be thought of as an unranked clade containing the families listed below. The biggest departure from earlier systems (see below) is the inclusion of family Araceae. By its inclusion, the order has grown enormously in number of species. The family Araceae alone accounts for about a hundred genera, totaling over two thousand species. The rest of the families together contain only about five hundred species, many of which are in very small families.
The APG III system (2009) differs only in that the Limnocharitaceae are combined with the Alismataceae; it was also suggested that the genus Maundia (of the Juncaginaceae) could be separated into a monogeneric family, the Maundiaceae, but the authors noted that more study was necessary before the Maundiaceae could be recognized.
order Alismatales sensu APG III
family Alismataceae (including Limnocharitaceae)
family Aponogetonaceae
family Araceae
family Butomaceae
family Cymodoceaceae
family Hydrocharitaceae
family Juncaginaceae
family Posidoniaceae
family Potamogetonaceae
family Ruppiaceae
family Scheuchzeriaceae
family Tofieldiaceae
family Zosteraceae
In APG IV (2016), it was decided that evidence was sufficient to elevate Maundia to family level as the monogeneric Maundiaceae. The authors considered including a number of the smaller orders within the Juncaginaceae, but an online survey of botanists and other users found little support for this "lumping" approach. Consequently, the family structure for APG IV is:
family Alismataceae (including Limnocharitaceae)
family Aponogetonaceae
family Araceae
family Butomaceae
family Cymodoceaceae
family Hydrocharitaceae
family Juncaginaceae
family Maundiaceae
family Posidoniaceae
family Potamogetonaceae
family Ruppiaceae
family Scheuchzeriaceae
family Tofieldiaceae
family Zosteraceae |
Alismatales | Phylogeny | Phylogeny
Cladogram showing the orders of monocots (Lilianae sensu Chase & Reveal) based on molecular phylogenetic evidence: |
Alismatales | References | References |
Alismatales | Further reading | Further reading
B. C. J. du Mortier 1829. Analyse des Familles de Plantes : avec l'indication des principaux genres qui s'y rattachent. Imprimerie de J. Casterman, Tournay
W. S. Judd, C. S. Campbell, E. A. Kellogg, P. F. Stevens, M. J. Donoghue, 2002. Plant Systematics: A Phylogenetic Approach, 2nd edition. Sinauer Associates, Sunderland, Massachusetts .
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Alismatales | External links | External links
Category:Angiosperm orders |
Alismatales | Table of Content | Short description, Description, Taxonomy, Early systems, Angiosperm Phylogeny Group, Phylogeny, References, Further reading, External links |
Apiales | Short description | The Apiales are an order of flowering plants, included in the asterid group of dicotyledons. Well-known members of Apiales include carrots, celery, coriander, parsley, parsnips, poison hemlock, ginseng, ivies, and pittosporums.
Apiales consist of nine families, with the type family being the celery, carrot or parsley family, Apiaceae. |
Apiales | Taxonomy | Taxonomy
There are nine accepted families within the Apiales, though there is some slight variation and in particular, the Torriceliaceae may also be divided.
Apiaceae (carrot family)
Araliaceae (ginseng family)
Griseliniaceae
Myodocarpaceae
Pennantiaceae
Pittosporaceae
Torricelliaceae
The present understanding of the Apiales is fairly recent and is based upon comparison of DNA sequences by phylogenetic methods. The circumscriptions of some of the families have changed. In 2009, one of the subfamilies of Araliaceae was shown to be polyphyletic.
The order Apiales is placed within the asterid group of eudicots as circumscribed by the APG III system. Within the asterids, Apiales belongs to an unranked group called the campanulids, and within the campanulids, it belongs to a clade known in phylogenetic nomenclature as Apiidae. In 2010, a subclade of Apiidae named Dipsapiidae was defined to consist of the three orders: Apiales, Paracryphiales, and Dipsacales.
Under the Cronquist system, only the Apiaceae and Araliaceae were included here, and the restricted order was placed among the rosids rather than the asterids. The Pittosporaceae were placed within the Rosales, and many of the other forms within the family Cornaceae. Pennantia was in the family Icacinaceae. In the classification system of Dahlgren the families Apiaceae and Araliaceae were placed in the order Ariales, in the superorder Araliiflorae (also called Aralianae). |
Apiales | Gynoecia | Gynoecia
The largest and obviously closely related families of Apiales are Araliaceae, Myodocarpaceae and
Apiaceae, which resemble each other in the structure of their gynoecia. In this respect however, the Pittosporaceae is notably distinct from them.
Typical syncarpous gynoecia exhibit four vertical zones, determined by the extent of fusion of the carpels. In most plants, the synascidiate (i.e. "united bottle-shaped") and symplicate zones are fertile and bear the ovules. Each of the first three families possess mainly bi- or multilocular ovaries in a gynoecium with a long synascidiate, but very short symplicate zone, where the ovules are inserted at their transition, the so-called cross-zone (or "Querzone").
In gynoecia of the Pittosporaceae, the symplicate is much longer than the synascidiate zone, and the ovules are arranged along the first. Members of the latter family consequently have unilocular ovaries with a single cavity between adjacent carpels. |
Apiales | References | References
Category:Angiosperm orders
Category:Taxa named by Takenoshin Nakai |
Apiales | Table of Content | Short description, Taxonomy, Gynoecia, References |
Asterales | Short description | Asterales ( ) is an order of dicotyledonous flowering plants that includes the large family Asteraceae (or Compositae) known for composite flowers made of florets, and ten families related to the Asteraceae. While asterids in general are characterized by fused petals, composite flowers consisting of many florets create the false appearance of separate petals (as found in the rosids).
The order is cosmopolitan (plants found throughout most of the world including desert and frigid zones), and includes mostly herbaceous species, although a small number of trees (such as the Lobelia deckenii, the giant lobelia, and Dendrosenecio, giant groundsels) and shrubs are also present.
Asterales are organisms that seem to have evolved from one common ancestor. Asterales share characteristics on morphological and biochemical levels. Synapomorphies (a character that is shared by two or more groups through evolutionary development) include the presence in the plants of oligosaccharide inulin, a nutrient storage molecule used instead of starch; and unique stamen morphology. The stamens are usually found around the style, either aggregated densely or fused into a tube, probably an adaptation in association with the plunger (brush; or secondary) pollination that is common among the families of the order, wherein pollen is collected and stored on the length of the pistil. |
Asterales | Taxonomy | Taxonomy
The name and order Asterales is botanically venerable, dating back to at least 1926 in the Hutchinson system of plant taxonomy when it contained only five families, of which only two are retained in the APG III classification. Under the Cronquist system of taxonomic classification of flowering plants, Asteraceae was the only family in the group, but newer systems (such as APG II and APG III) have expanded it to 11. In the classification system of Rolf Dahlgren the Asterales were in the superorder Asteriflorae (also called Asteranae).
The order Asterales currently includes 11 families, the largest of which are the Asteraceae, with about 25,000 species, and the Campanulaceae (bellflowers), with about 2,000 species. The remaining families count together for less than 1500 species. The two large families are cosmopolitan, with many of their species found in the Northern Hemisphere, and the smaller families are usually confined to Australia and the adjacent areas, or sometimes South America.
Only the Asteraceae have composite flower heads; the other families do not, but share other characteristics such as storage of inulin that define the 11 families as more closely related to each other than to other plant families or orders such as the rosids.
The phylogenetic tree according to APG III for the Campanulid clade is as below. |
Asterales | Phylogeny | Phylogeny
Although most extant species of Asteraceae are herbaceous, the examination of the basal members in the family suggests that the common ancestor of the family was an arborescent plant, a tree or shrub, perhaps adapted to dry conditions, radiating from South America. Less can be said about the Asterales themselves with certainty, although since several families in Asterales contain trees, the ancestral member is most likely to have been a tree or shrub.
Because all clades are represented in the Southern Hemisphere but many not in the Northern Hemisphere, it is natural to conjecture that there is a common southern origin to them. Asterales belong to angiosperms or flowering plants, a clade that appeared about 140 million years ago. The Asterales order probably originated in the Cretaceous (145 – 66 Mya) on the supercontinent Gondwana which broke up from 184 – 80 Mya, forming the area that is now Australia, South America, Africa, India and Antarctica.
Asterales contain about 14% of eudicot diversity. From an analysis of relationships and diversities within the Asterales and with their superorders, estimates of the age of the beginning of the Asterales have been made, which range from 116 Mya to 82Mya. However few fossils have been found, of the Menyanthaceae-Asteraceae clade in the Oligocene, about 29 Mya.
Fossil evidence of the Asterales is rare and belongs to rather recent epochs, so the precise estimation of the order's age is quite difficult. An Oligocene (34 – 23 Mya) pollen is known for Asteraceae and Goodeniaceae, and seeds from Oligocene and Miocene (23 – 5.3 Mya) are known for Menyanthaceae and Campanulaceae respectively. According to molecular clock calculations, the lineage that led to Asterales split from other plants about 112 million years ago or 94 million years ago. |
Asterales | Biogeography | Biogeography
The core Asterales are Stylidiaceae (six genera), APA clade (Alseuosmiaceae, Phellinaceae and Argophyllaceae, together seven genera), MGCA clade (Menyanthaceae, Goodeniaceae, Calyceraceae, in total twenty genera), and Asteraceae (about sixteen hundred genera). Other Asterales are Rousseaceae (four genera), Campanulaceae (eighty-four genera) and Pentaphragmataceae (one genus).
All Asterales families are represented in the Southern Hemisphere; however, Asteraceae and Campanulaceae are cosmopolitan and Menyanthaceae nearly so. |
Asterales | Uses | Uses
The Asterales, by dint of being a super-set of the family Asteraceae, include some species grown for food, including the sunflower (Helianthus annuus), lettuce (Lactuca sativa) and chicory (Cichorium). Many are also used as spices and traditional medicines.
Asterales are common plants and have many known uses. For example, pyrethrum (derived from Old World members of the genus Chrysanthemum) is a natural insecticide with minimal environmental impact. Wormwood, derived from a genus that includes the sagebrush, is used as a source of flavoring for absinthe, a bitter classical liquor of European origin. |
Asterales | References | References |
Asterales | Further reading | Further reading
W. S. Judd, C. S. Campbell, E. A. Kellogg, P. F. Stevens, M. J. Donoghue (2002). Plant Systematics: A Phylogenetic Approach, 2nd edition. pp. 476–486 (Asterales). Sinauer Associates, Sunderland, Massachusetts. .
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Asterales | External links | External links
Category:Angiosperm orders |
Asterales | Table of Content | Short description, Taxonomy, Phylogeny, Biogeography, Uses, References, Further reading, External links |
Asteroid | Short description | An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type (carbonaceous), M-type (metallic), or S-type (silicaceous). The size and shape of asteroids vary significantly, ranging from small rubble piles under a kilometer across to Ceres, a dwarf planet almost 1000 km in diameter. A body is classified as a comet, not an asteroid, if it shows a coma (tail) when warmed by solar radiation, although recent observations suggest a continuum between these types of bodies.
Of the roughly one million known asteroids, the greatest number are located between the orbits of Mars and Jupiter, approximately 2 to 4 AU from the Sun, in a region known as the main asteroid belt. The total mass of all the asteroids combined is only 3% that of Earth's Moon. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun.
Asteroids have historically been observed from Earth. The first close-up observation of an asteroid was made by the Galileo spacecraft. Several dedicated missions to asteroids were subsequently launched by NASA and JAXA, with plans for other missions in progress. NASA's NEAR Shoemaker studied Eros, and Dawn observed Vesta and Ceres. JAXA's missions Hayabusa and Hayabusa2 studied and returned samples of Itokawa and Ryugu, respectively. OSIRIS-REx studied Bennu, collecting a sample in 2020 which was delivered back to Earth in 2023. NASA's Lucy, launched in 2021, is tasked with studying ten different asteroids, two from the main belt and eight Jupiter trojans. Psyche, launched October 2023, aims to study the metallic asteroid Psyche.
Near-Earth asteroids have the potential for catastrophic consequences if they strike Earth, with a notable example being the Chicxulub impact, widely thought to have induced the Cretaceous–Paleogene mass extinction. As an experiment to meet this danger, in September 2022 the Double Asteroid Redirection Test spacecraft successfully altered the orbit of the non-threatening asteroid Dimorphos by crashing into it. |
Asteroid | Terminology{{anchor | Terminology
In 2006, the International Astronomical Union (IAU) introduced the currently preferred broad term small Solar System body, defined as an object in the Solar System that is neither a planet, a dwarf planet, nor a natural satellite; this includes asteroids, comets, and more recently discovered classes. According to IAU, "the term 'minor planet' may still be used, but generally, 'Small Solar System Body' will be preferred."
Historically, the first discovered asteroid, Ceres, was at first considered a new planet. It was followed by the discovery of other similar bodies, which with the equipment of the time appeared to be points of light like stars, showing little or no planetary disc, though readily distinguishable from stars due to their apparent motions. This prompted the astronomer Sir William Herschel to propose the term asteroid, coined in Greek as ἀστεροειδής, or asteroeidēs, meaning 'star-like, star-shaped', and derived from the Ancient Greek astēr 'star, planet'. In the early second half of the 19th century, the terms asteroid and planet (not always qualified as "minor") were still used interchangeably.
Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than one meter across being called a meteoroid. The term asteroid, never officially defined, can be informally used to mean "an irregularly shaped rocky body orbiting the Sun that does not qualify as a planet or a dwarf planet under the IAU definitions". The main difference between an asteroid and a comet is that a comet shows a coma (tail) due to sublimation of its near-surface ices by solar radiation. A few objects were first classified as minor planets but later showed evidence of cometary activity. Conversely, some (perhaps all) comets are eventually depleted of their surface volatile ices and become asteroid-like. A further distinction is that comets typically have more eccentric orbits than most asteroids; highly eccentric asteroids are probably dormant or extinct comets.
The minor planets beyond Jupiter's orbit are sometimes also called "asteroids", especially in popular presentations. However, it is becoming increasingly common for the term asteroid to be restricted to minor planets of the inner Solar System. Therefore, this article will restrict itself for the most part to the classical asteroids: objects of the asteroid belt, Jupiter trojans, and near-Earth objects.
For almost two centuries after the discovery of Ceres in 1801, all known asteroids spent most of their time at or within the orbit of Jupiter, though a few, such as 944 Hidalgo, ventured farther for part of their orbit. Starting in 1977 with 2060 Chiron, astronomers discovered small bodies that permanently resided further out than Jupiter, now called centaurs. In 1992, 15760 Albion was discovered, the first object beyond the orbit of Neptune (other than Pluto); soon large numbers of similar objects were observed, now called trans-Neptunian object. Further out are Kuiper-belt objects, scattered-disc objects, and the much more distant Oort cloud, hypothesized to be the main reservoir of dormant comets. They inhabit the cold outer reaches of the Solar System where ices remain solid and comet-like bodies exhibit little cometary activity; if centaurs or trans-Neptunian objects were to venture close to the Sun, their volatile ices would sublimate, and traditional approaches would classify them as comets.
The Kuiper-belt bodies are called "objects" partly to avoid the need to classify them as asteroids or comets. They are thought to be predominantly comet-like in composition, though some may be more akin to asteroids. Most do not have the highly eccentric orbits associated with comets, and the ones so far discovered are larger than traditional comet nuclei. Other recent observations, such as the analysis of the cometary dust collected by the Stardust probe, are increasingly blurring the distinction between comets and asteroids, suggesting "a continuum between asteroids and comets" rather than a sharp dividing line.
In 2006, the IAU created the class of dwarf planets for the largest minor planets—those massive enough to have become ellipsoidal under their own gravity. Only the largest object in the asteroid belt has been placed in this category: Ceres, at about across. |
Asteroid | History of observations | History of observations
Despite their large numbers, asteroids are a relatively recent discovery, with the first one—Ceres—only being identified in 1801. Only one asteroid, 4 Vesta, which has a relatively reflective surface, is normally visible to the naked eye in dark skies when it is favorably positioned. Rarely, small asteroids passing close to Earth may be briefly visible to the naked eye. , the Minor Planet Center had data on 1,199,224 minor planets in the inner and outer Solar System, of which about 614,690 had enough information to be given numbered designations. |
Asteroid | Discovery of Ceres | Discovery of Ceres
In 1772, German astronomer Johann Elert Bode, citing Johann Daniel Titius, published a numerical procession known as the Titius–Bode law (now discredited). Except for an unexplained gap between Mars and Jupiter, Bode's formula seemed to predict the orbits of the known planets. He wrote the following explanation for the existence of a "missing planet":
This latter point seems in particular to follow from the astonishing relation which the known six planets observe in their distances from the Sun. Let the distance from the Sun to Saturn be taken as 100, then Mercury is separated by 4 such parts from the Sun. Venus is 4 + 3 = 7. The Earth 4 + 6 = 10. Mars 4 + 12 = 16. Now comes a gap in this so orderly progression. After Mars there follows a space of 4 + 24 = 28 parts, in which no planet has yet been seen. Can one believe that the Founder of the universe had left this space empty? Certainly not. From here we come to the distance of Jupiter by 4 + 48 = 52 parts, and finally to that of Saturn by 4 + 96 = 100 parts.
Bode's formula predicted another planet would be found with an orbital radius near 2.8 astronomical units (AU), or 420 million km, from the Sun. The Titius–Bode law got a boost with William Herschel's discovery of Uranus near the predicted distance for a planet beyond Saturn. In 1800, a group headed by Franz Xaver von Zach, editor of the German astronomical journal Monatliche Correspondenz (Monthly Correspondence), sent requests to 24 experienced astronomers (whom he dubbed the "celestial police"), asking that they combine their efforts and begin a methodical search for the expected planet. Although they did not discover Ceres, they later found the asteroids 2 Pallas, 3 Juno and 4 Vesta.
One of the astronomers selected for the search was Giuseppe Piazzi, a Catholic priest at the Academy of Palermo, Sicily. Before receiving his invitation to join the group, Piazzi discovered Ceres on 1 January 1801. He was searching for "the 87th [star] of the Catalogue of the Zodiacal stars of Mr la Caille", but found that "it was preceded by another". Instead of a star, Piazzi had found a moving star-like object, which he first thought was a comet:
The light was a little faint, and of the colour of Jupiter, but similar to many others which generally are reckoned of the eighth magnitude. Therefore I had no doubt of its being any other than a fixed star. [...] The evening of the third, my suspicion was converted into certainty, being assured it was not a fixed star. Nevertheless before I made it known, I waited till the evening of the fourth, when I had the satisfaction to see it had moved at the same rate as on the preceding days.
Piazzi observed Ceres a total of 24 times, the final time on 11 February 1801, when illness interrupted his work. He announced his discovery on 24 January 1801 in letters to only two fellow astronomers, his compatriot Barnaba Oriani of Milan and Bode in Berlin. He reported it as a comet but "since its movement is so slow and rather uniform, it has occurred to me several times that it might be something better than a comet". In April, Piazzi sent his complete observations to Oriani, Bode, and French astronomer Jérôme Lalande. The information was published in the September 1801 issue of the Monatliche Correspondenz.
By this time, the apparent position of Ceres had changed (mostly due to Earth's motion around the Sun), and was too close to the Sun's glare for other astronomers to confirm Piazzi's observations. Toward the end of the year, Ceres should have been visible again, but after such a long time it was difficult to predict its exact position. To recover Ceres, mathematician Carl Friedrich Gauss, then 24 years old, developed an efficient method of orbit determination. In a few weeks, he predicted the path of Ceres and sent his results to von Zach. On 31 December 1801, von Zach and fellow celestial policeman Heinrich W. M. Olbers found Ceres near the predicted position and thus recovered it. At 2.8 AU from the Sun, Ceres appeared to fit the Titius–Bode law almost perfectly; however, Neptune, once discovered in 1846, was 8 AU closer than predicted, leading most astronomers to conclude that the law was a coincidence. Piazzi named the newly discovered object Ceres Ferdinandea, "in honor of the patron goddess of Sicily and of King Ferdinand of Bourbon". |
Asteroid | Further search | Further search
thumb|left|Sizes of the first ten discovered asteroids, compared to the Moon
Three other asteroids (2 Pallas, 3 Juno, and 4 Vesta) were discovered by von Zach's group over the next few years, with Vesta found in 1807. No new asteroids were discovered until 1845. Amateur astronomer Karl Ludwig Hencke started his searches of new asteroids in 1830, and fifteen years later, while looking for Vesta, he found the asteroid later named 5 Astraea. It was the first new asteroid discovery in 38 years. Carl Friedrich Gauss was given the honor of naming the asteroid. After this, other astronomers joined; 15 asteroids were found by the end of 1851. In 1868, when James Craig Watson discovered the 100th asteroid, the French Academy of Sciences engraved the faces of Karl Theodor Robert Luther, John Russell Hind, and Hermann Goldschmidt, the three most successful asteroid-hunters at that time, on a commemorative medallion marking the event.
In 1891, Max Wolf pioneered the use of astrophotography to detect asteroids, which appeared as short streaks on long-exposure photographic plates. This dramatically increased the rate of detection compared with earlier visual methods: Wolf alone discovered 248 asteroids, beginning with 323 Brucia, whereas only slightly more than 300 had been discovered up to that point. It was known that there were many more, but most astronomers did not bother with them, some calling them "vermin of the skies", a phrase variously attributed to Eduard Suess and Edmund Weiss. Even a century later, only a few thousand asteroids were identified, numbered and named. |
Asteroid | 19th and 20th centuries | 19th and 20th centuries
thumb|Cumulative discoveries of just the near-Earth asteroids known by size, 1980–2024
In the past, asteroids were discovered by a four-step process. First, a region of the sky was photographed by a wide-field telescope or astrograph. Pairs of photographs were taken, typically one hour apart. Multiple pairs could be taken over a series of days. Second, the two films or plates of the same region were viewed under a stereoscope. A body in orbit around the Sun would move slightly between the pair of films. Under the stereoscope, the image of the body would seem to float slightly above the background of stars. Third, once a moving body was identified, its location would be measured precisely using a digitizing microscope. The location would be measured relative to known star locations.
These first three steps do not constitute asteroid discovery: the observer has only found an apparition, which gets a provisional designation, made up of the year of discovery, a letter representing the half-month of discovery, and finally a letter and a number indicating the discovery's sequential number (example: ). The last step is sending the locations and time of observations to the Minor Planet Center, where computer programs determine whether an apparition ties together earlier apparitions into a single orbit. If so, the object receives a catalogue number and the observer of the first apparition with a calculated orbit is declared the discoverer, and granted the honor of naming the object subject to the approval of the International Astronomical Union. |
Asteroid | Naming | Naming
thumb|right|2013 EC, shown here in radar images, has a provisional designation
By 1851, the Royal Astronomical Society decided that asteroids were being discovered at such a rapid rate that a different system was needed to categorize or name asteroids. In 1852, when de Gasparis discovered the twentieth asteroid, Benjamin Valz gave it a name and a number designating its rank among asteroid discoveries, 20 Massalia. Sometimes asteroids were discovered and not seen again. So, starting in 1892, new asteroids were listed by the year and a capital letter indicating the order in which the asteroid's orbit was calculated and registered within that specific year. For example, the first two asteroids discovered in 1892 were labeled 1892A and 1892B. However, there were not enough letters in the alphabet for all of the asteroids discovered in 1893, so 1893Z was followed by 1893AA. A number of variations of these methods were tried, including designations that included year plus a Greek letter in 1914. A simple chronological numbering system was established in 1925.
Currently all newly discovered asteroids receive a provisional designation (such as ) consisting of the year of discovery and an alphanumeric code indicating the half-month of discovery and the sequence within that half-month. Once an asteroid's orbit has been confirmed, it is given a number, and later may also be given a name (e.g. ). The formal naming convention uses parentheses around the number—e.g. (433) Eros—but dropping the parentheses is quite common. Informally, it is also common to drop the number altogether, or to drop it after the first mention when a name is repeated in running text. In addition, names can be proposed by the asteroid's discoverer, within guidelines established by the International Astronomical Union. |
Asteroid | Symbols | Symbols
The first asteroids to be discovered were assigned iconic symbols like the ones traditionally used to designate the planets. By 1852 there were two dozen asteroid symbols, which often occurred in multiple variants.
In 1851, after the fifteenth asteroid, Eunomia, had been discovered, Johann Franz Encke made a major change in the upcoming 1854 edition of the Berliner Astronomisches Jahrbuch (BAJ, Berlin Astronomical Yearbook). He introduced a disk (circle), a traditional symbol for a star, as the generic symbol for an asteroid. The circle was then numbered in order of discovery to indicate a specific asteroid. The numbered-circle convention was quickly adopted by astronomers, and the next asteroid to be discovered (16 Psyche, in 1852) was the first to be designated in that way at the time of its discovery. However, Psyche was given an iconic symbol as well, as were a few other asteroids discovered over the next few years. 20 Massalia was the first asteroid that was not assigned an iconic symbol, and no iconic symbols were created after the 1855 discovery of 37 Fides. |
Asteroid | Formation | Formation
Many asteroids are the shattered remnants of planetesimals, bodies within the young Sun's solar nebula that never grew large enough to become planets. It is thought that planetesimals in the asteroid belt evolved much like the rest of objects in the solar nebula until Jupiter neared its current mass, at which point excitation from orbital resonances with Jupiter ejected over 99% of planetesimals in the belt. Simulations and a discontinuity in spin rate and spectral properties suggest that asteroids larger than approximately in diameter accreted during that early era, whereas smaller bodies are fragments from collisions between asteroids during or after the Jovian disruption. Ceres and Vesta grew large enough to melt and differentiate, with heavy metallic elements sinking to the core, leaving rocky minerals in the crust.
In the Nice model, many Kuiper-belt objects are captured in the outer asteroid belt, at distances greater than 2.6 AU. Most were later ejected by Jupiter, but those that remained may be the D-type asteroids, and possibly include Ceres. |
Asteroid | Distribution within the Solar System | Distribution within the Solar System
thumb|A top view of asteroid group location in the inner solar system|350x350px
thumb|A map of planets and asteroid groups of the inner solar system. Distances from sun are to scale, object sizes are not.
Various dynamical groups of asteroids have been discovered orbiting in the inner Solar System. Their orbits are perturbed by the gravity of other bodies in the Solar System and by the Yarkovsky effect. Significant populations include: |
Asteroid | Asteroid belt | Asteroid belt
The majority of known asteroids orbit within the asteroid belt between the orbits of Mars and Jupiter, generally in relatively low-eccentricity (i.e. not very elongated) orbits. This belt is estimated to contain between 1.1 and 1.9 million asteroids larger than in diameter, and millions of smaller ones. These asteroids may be remnants of the protoplanetary disk, and in this region the accretion of planetesimals into planets during the formative period of the Solar System was prevented by large gravitational perturbations by Jupiter.
Contrary to popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that reaching an asteroid without aiming carefully would be improbable. Nonetheless, hundreds of thousands of asteroids are currently known, and the total number ranges in the millions or more, depending on the lower size cutoff. Over 200 asteroids are known to be larger than 100 km, and a survey in the infrared wavelengths has shown that the asteroid belt has between 700,000 and 1.7 million asteroids with a diameter of 1 km or more. The absolute magnitudes of most of the known asteroids are between 11 and 19, with the median at about 16.
The total mass of the asteroid belt is estimated to be kg, which is just 3% of the mass of the Moon; the mass of the Kuiper Belt and Scattered Disk is over 100 times as large. The four largest objects, Ceres, Vesta, Pallas, and Hygiea, account for maybe 62% of the belt's total mass, with 39% accounted for by Ceres alone. |
Asteroid | Trojans | Trojans
Trojans are populations that share an orbit with a larger planet or moon, but do not collide with it because they orbit in one of the two Lagrangian points of stability, and , which lie 60° ahead of and behind the larger body.
In the Solar System, most known trojans share the orbit of Jupiter. They are divided into the Greek camp at (ahead of Jupiter) and the Trojan camp at (trailing Jupiter). More than a million Jupiter trojans larger than one kilometer are thought to exist, of which more than 7,000 are currently catalogued. In other planetary orbits only nine Mars trojans, 28 Neptune trojans, two Uranus trojans, and two Earth trojans, have been found to date. A temporary Venus trojan is also known. Numerical orbital dynamics stability simulations indicate that Saturn and Uranus probably do not have any primordial trojans. |
Asteroid | Near-Earth asteroids | Near-Earth asteroids
Near-Earth asteroids, or NEAs, are asteroids that have orbits that pass close to that of Earth. Asteroids that actually cross Earth's orbital path are known as Earth-crossers. , a total of 28,772 near-Earth asteroids were known; 878 have a diameter of one kilometer or larger.
A small number of NEAs are extinct comets that have lost their volatile surface materials, although having a faint or intermittent comet-like tail does not necessarily result in a classification as a near-Earth comet, making the boundaries somewhat fuzzy. The rest of the near-Earth asteroids are driven out of the asteroid belt by gravitational interactions with Jupiter.
Many asteroids have natural satellites (minor-planet moons). , there were 85 NEAs known to have at least one moon, including three known to have two moons. The asteroid 3122 Florence, one of the largest potentially hazardous asteroids with a diameter of , has two moons measuring across, which were discovered by radar imaging during the asteroid's 2017 approach to Earth.
Near-Earth asteroids are divided into groups based on their semi-major axis (a), perihelion distance (q), and aphelion distance (Q):
The Atiras or Apoheles have orbits strictly inside Earth's orbit: an Atira asteroid's aphelion distance (Q) is smaller than Earth's perihelion distance (0.983 AU). That is, , which implies that the asteroid's semi-major axis is also less than 0.983 AU.
The Atens have a semi-major axis of less than 1 AU and cross Earth's orbit. Mathematically, and . (0.983 AU is Earth's perihelion distance.)
The Apollos have a semi-major axis of more than 1 AU and cross Earth's orbit. Mathematically, and . (1.017 AU is Earth's aphelion distance.)
The Amors have orbits strictly outside Earth's orbit: an Amor asteroid's perihelion distance (q) is greater than Earth's aphelion distance (1.017 AU). Amor asteroids are also near-earth objects so . In summary, . (This implies that the asteroid's semi-major axis (a) is also larger than 1.017 AU.) Some Amor asteroid orbits cross the orbit of Mars. |
Asteroid | Martian moons | Martian moons
It is unclear whether Martian moons Phobos and Deimos are captured asteroids or were formed due to impact event on Mars.Burns, Joseph A. (1992). "Contradictory Clues as to the Origin of the Martian Moons" in Mars, H. H. Kieffer et al., eds., Tucson: University of Arizona Press, Tucson Phobos and Deimos both have much in common with carbonaceous C-type asteroids, with spectra, albedo, and density very similar to those of C- or D-type asteroids. Based on their similarity, one hypothesis is that both moons may be captured main-belt asteroids.Landis, Geoffrey A.; "Origin of Martian Moons from Binary Asteroid Dissociation", American Association for the Advancement of Science Annual Meeting; Boston, MA, 2001, abstract Both moons have very circular orbits which lie almost exactly in Mars's equatorial plane, and hence a capture origin requires a mechanism for circularizing the initially highly eccentric orbit, and adjusting its inclination into the equatorial plane, most probably by a combination of atmospheric drag and tidal forces, although it is not clear whether sufficient time was available for this to occur for Deimos. Capture also requires dissipation of energy. The current Martian atmosphere is too thin to capture a Phobos-sized object by atmospheric braking. Geoffrey A. Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated under tidal forces.
Phobos could be a second-generation Solar System object that coalesced in orbit after Mars formed, rather than forming concurrently out of the same birth cloud as Mars.
Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal.Craddock, Robert A.; (1994); "The Origin of Phobos and Deimos", Abstracts of the 25th Annual Lunar and Planetary Science Conference, held in Houston, TX, 14–18 March 1994, p. 293 The high porosity of the interior of Phobos (based on the density of 1.88 g/cm3, voids are estimated to comprise 25 to 35 percent of Phobos's volume) is inconsistent with an asteroidal origin. Observations of Phobos in the thermal infrared suggest a composition containing mainly phyllosilicates, which are well known from the surface of Mars. The spectra are distinct from those of all classes of chondrite meteorites, again pointing away from an asteroidal origin. Both sets of findings support an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's moon. |
Asteroid | Characteristics | Characteristics |
Asteroid | Size distribution | Size distribution
thumb|The asteroids of the Solar System, categorized by size and number|300x300px
Asteroids vary greatly in size, from almost for the largest down to rocks just 1 meter across, below which an object is classified as a meteoroid. The three largest are very much like miniature planets: they are roughly spherical, have at least partly differentiated interiors, and are thought to be surviving protoplanets. The vast majority, however, are much smaller and are irregularly shaped; they are thought to be either battered planetesimals or fragments of larger bodies.
The dwarf planet Ceres is by far the largest asteroid, with a diameter of . The next largest are 4 Vesta and 2 Pallas, both with diameters of just over . Vesta is the brightest of the four main-belt asteroids that can, on occasion, be visible to the naked eye. On some rare occasions, a near-Earth asteroid may briefly become visible without technical aid; see 99942 Apophis.
The mass of all the objects of the asteroid belt, lying between the orbits of Mars and Jupiter, is estimated to be , ≈ 3.25% of the mass of the Moon. Of this, Ceres comprises , about 40% of the total. Adding in the next three most massive objects, Vesta (11%), Pallas (8.5%), and Hygiea (3–4%), brings this figure up to a bit over 60%, whereas the next seven most-massive asteroids bring the total up to 70%. The number of asteroids increases rapidly as their individual masses decrease.
The number of asteroids decreases markedly with increasing size. Although the size distribution generally follows a power law, there are 'bumps' at about and , where more asteroids than expected from such a curve are found. Most asteroids larger than approximately 120 km in diameter are primordial (surviving from the accretion epoch), whereas most smaller asteroids are products of fragmentation of primordial asteroids. The primordial population of the main belt was probably 200 times what it is today. |
Asteroid | Largest asteroids | Largest asteroids
Three largest objects in the asteroid belt, Ceres, Vesta, and Pallas, are intact protoplanets that share many characteristics common to planets, and are atypical compared to the majority of irregularly shaped asteroids. The fourth-largest asteroid, Hygiea, appears nearly spherical although it may have an undifferentiated interior, like the majority of asteroids. The four largest asteroids constitute half the mass of the asteroid belt.
Ceres is the only asteroid that appears to have a plastic shape under its own gravity and hence the only one that is a dwarf planet. It has a much higher absolute magnitude than the other asteroids, of around 3.32, and may possess a surface layer of ice. Like the planets, Ceres is differentiated: it has a crust, a mantle and a core. No meteorites from Ceres have been found on Earth.
Vesta, too, has a differentiated interior, though it formed inside the Solar System's frost line, and so is devoid of water; its composition is mainly of basaltic rock with minerals such as olivine. Aside from the large crater at its southern pole, Rheasilvia, Vesta also has an ellipsoidal shape. Vesta is the parent body of the Vestian family and other V-type asteroids, and is the source of the HED meteorites, which constitute 5% of all meteorites on Earth.
Pallas is unusual in that, like Uranus, it rotates on its side, with its axis of rotation tilted at high angles to its orbital plane. Its composition is similar to that of Ceres: high in carbon and silicon, and perhaps partially differentiated. Pallas is the parent body of the Palladian family of asteroids.
Hygiea is the largest carbonaceous asteroid and, unlike the other largest asteroids, lies relatively close to the plane of the ecliptic. It is the largest member and presumed parent body of the Hygiean family of asteroids. Because there is no sufficiently large crater on the surface to be the source of that family, as there is on Vesta, it is thought that Hygiea may have been completely disrupted in the collision that formed the Hygiean family and recoalesced after losing a bit less than 2% of its mass. Observations taken with the Very Large Telescope's SPHERE imager in 2017 and 2018, revealed that Hygiea has a nearly spherical shape, which is consistent both with it being in hydrostatic equilibrium, or formerly being in hydrostatic equilibrium, or with being disrupted and recoalescing.
Internal differentiation of large asteroids is possibly related to their lack of natural satellites, as satellites of main belt asteroids are mostly believed to form from collisional disruption, creating a rubble pile structure.
+ Attributes of largest asteroidsNameOrbitalradius(AU)Orbitalperiod(years)Inclinationto eclipticOrbitaleccentricity Diameter(km) Diameter(% of Moon) Mass( kg) Mass(% of Ceres) Density(g/cm3) Rotationperiod(hr) Ceres 2.77 4.60 10.6° 0.079 964×964×892(mean 939.4) 27% 938 100% 2.16±0.01 9.07 Vesta 2.36 3.63 7.1° 0.089 573×557×446(mean 525.4) 15% 259 28% 3.46 ± 0.04 5.34 Pallas 2.77 4.62 34.8° 0.231 550×516×476(mean 511±4) 15% 204±3 21% 2.92±0.08 7.81 Hygiea 3.14 5.56 3.8° 0.117 450×430×424(mean 433±8) 12% 87±7 9% 2.06±0.20 13.8 |
Asteroid | Rotation | Rotation
Measurements of the rotation rates of large asteroids in the asteroid belt show that there is an upper limit. Very few asteroids with a diameter larger than 100 meters have a rotation period less than 2.2 hours. For asteroids rotating faster than approximately this rate, the inertial force at the surface is greater than the gravitational force, so any loose surface material would be flung out. However, a solid object should be able to rotate much more rapidly. This suggests that most asteroids with a diameter over 100 meters are rubble piles formed through the accumulation of debris after collisions between asteroids. |
Asteroid | Color | Color
Asteroids become darker and redder with age due to space weathering. However evidence suggests most of the color change occurs rapidly, in the first hundred thousand years, limiting the usefulness of spectral measurement for determining the age of asteroids. |
Asteroid | Surface features | Surface features
thumb|Cratered terrain on 4 Vesta
Except for the "big four" (Ceres, Pallas, Vesta, and Hygiea), asteroids are likely to be broadly similar in appearance, if irregular in shape. 253 Mathilde is a rubble pile saturated with craters with diameters the size of the asteroid's radius. Earth-based observations of 511 Davida, one of the largest asteroids after the big four, reveal a similarly angular profile, suggesting it is also saturated with radius-size craters. Medium-sized asteroids such as Mathilde and 243 Ida, that have been observed up close, also reveal a deep regolith covering the surface. Of the big four, Pallas and Hygiea are practically unknown. Vesta has compression fractures encircling a radius-size crater at its south pole but is otherwise a spheroid.
Dawn spacecraft revealed that Ceres has a heavily cratered surface, but with fewer large craters than expected. Models based on the formation of the current asteroid belt had suggested Ceres should possess 10 to 15 craters larger than in diameter. The largest confirmed crater on Ceres, Kerwan Basin, is across. The most likely reason for this is viscous relaxation of the crust slowly flattening out larger impacts. |
Asteroid | Composition | Composition
Asteroids are classified by their characteristic emission spectra, with the majority falling into three main groups: C-type, M-type, and S-type. These describe carbonaceous (carbon-rich), metallic, and silicaceous (stony) compositions, respectively. The physical composition of asteroids is varied and in most cases poorly understood. Ceres appears to be composed of a rocky core covered by an icy mantle; Vesta is thought to have a nickel-iron core, olivine mantle, and basaltic crust. Thought to be the largest undifferentiated asteroid, 10 Hygiea seems to have a uniformly primitive composition of carbonaceous chondrite, but it may actually be a differentiated asteroid that was globally disrupted by an impact and then reassembled. Other asteroids appear to be the remnant cores or mantles of proto-planets, high in rock and metal. Most small asteroids are believed to be piles of rubble held together loosely by gravity, although the largest are probably solid. Some asteroids have moons or are co-orbiting binaries: rubble piles, moons, binaries, and scattered asteroid families are thought to be the results of collisions that disrupted a parent asteroid, or possibly a planet.
In the main asteroid belt, there appear to be two primary populations of asteroid: a dark, volatile-rich population, consisting of the C-type and P-type asteroids, with albedos less than 0.10 and densities under , and a dense, volatile-poor population, consisting of the S-type and M-type asteroids, with albedos over 0.15 and densities greater than 2.7. Within these populations, larger asteroids are denser, presumably due to compression. There appears to be minimal macro-porosity (interstitial vacuum) in the score of asteroids with masses greater than .P. Vernazza et al. (2021) VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis. Astronomy & Astrophysics 54, A56
Composition is calculated from three primary sources: albedo, surface spectrum, and density. The last can only be determined accurately by observing the orbits of moons the asteroid might have. So far, every asteroid with moons has turned out to be a rubble pile, a loose conglomeration of rock and metal that may be half empty space by volume. The investigated asteroids are as large as 280 km in diameter, and include 121 Hermione (268×186×183 km), and 87 Sylvia (384×262×232 km). Few asteroids are larger than 87 Sylvia, none of them have moons. The fact that such large asteroids as Sylvia may be rubble piles, presumably due to disruptive impacts, has important consequences for the formation of the Solar System: computer simulations of collisions involving solid bodies show them destroying each other as often as merging, but colliding rubble piles are more likely to merge. This means that the cores of the planets could have formed relatively quickly. |
Asteroid | Water | Water
Scientists hypothesize that some of the first water brought to Earth was delivered by asteroid impacts after the collision that produced the Moon. In 2009, the presence of water ice was confirmed on the surface of 24 Themis using NASA's Infrared Telescope Facility. The surface of the asteroid appears completely covered in ice. As this ice layer is sublimating, it may be getting replenished by a reservoir of ice under the surface. Organic compounds were also detected on the surface. The presence of ice on 24 Themis makes the initial theory plausible.
In October 2013, water was detected on an extrasolar body for the first time, on an asteroid orbiting the white dwarf GD 61. On 22 January 2014, European Space Agency (ESA) scientists reported the detection, for the first definitive time, of water vapor on Ceres, the largest object in the asteroid belt. The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes". According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids."
Findings have shown that solar winds can react with the oxygen in the upper layer of the asteroids and create water. It has been estimated that "every cubic metre of irradiated rock could contain up to 20 litres"; study was conducted using an atom probe tomography, numbers are given for the Itokawa S-type asteroid.
Acfer 049, a meteorite discovered in Algeria in 1990, was shown in 2019 to have an ultraporous lithology (UPL): porous texture that could be formed by removal of ice that filled these pores, this suggests that UPL "represent fossils of primordial ice". |
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