text:   Protoplanetary Disks",8,"['Can we measure total protoplanetary disk mass without assuming a tracer-to-H2 ratio? Check out our new paper on the locations of planet formation where we derive total gaseous surface densities for 7 protoplanetary disks using dust lines! <LINK>', 'The disks in our sample have newly derived masses that are 9-27% of their host stellar mass, substantially larger than the minimum mass solar nebula! All are stable to gravitational collapse except for one which approaches the limit of Toomre-Q stability.', 'These masses are determined independent of an assumed dust opacity!', 'Check out how the new total surface densities compared to previously derived values and the minimum mass solar nebula! These are massive disks! https://t.co/d4PhLzwPsA', 'Our mass estimates are 2-15 times larger than estimates from integrated optically thin dust emission.  In these models, the disks formed with an initial dust mass that is a factor of ∼10 greater than is presently observed. More dust mass at early times!', 'Of the three disks in our sample with resolved CO line emission, the masses of HD 163296, AS 209, and TW Hya are roughly 3, 115, and 40 times more massive than estimates from CO respectively. More evidence that the CO story in disks is complicated!', 'Our method of determining surface density using dust lines is robust even if particles form as aggregates and is useful even in the presence of dust substructure caused by pressure traps. https://t.co/gmVGS7NNPx', 'The low Toomre-Q values observed in this sample indicate that at least some disks do not accrete efficiently. https://t.co/P9Vf2aj4jX']",19,05,1534