text: 153,29,1043036765680889856,776765039726460929,Carlo Felice Manara,"1/4 New paper based on @almaobs <LINK> @ESO VLT/X-Shooter #GaiaDR2 data: ""Why do protoplanetary disks appear not massive enough to form the known exoplanet population?"" <LINK> with A LOT of help from Alessandro Morbidelli and Tristan Guillot <LINK> 2/4 Take home: we do not have enough mass in disks at 1-3 Myr to explain exoplanetary systems, even when considering the mass in solids in disks vs the mass of solids in planets. This is now true for a large range of stellar masses covered both in disks and exoplanet surveys <LINK> 3/4 Possible solutions: 0) protoplanetary disk masses are underestimated (but I have reasons to believe this is not the case) 1) cores of planets have formed very rapidly (&lt;0.1-1 Myr) 2) disks are continuously replenished of fresh planet-forming material from the environment 4/4 I want to also point to (some of the) relevant references for the various points: 0) <LINK> <LINK> 1) <LINK> <LINK> <LINK> 2) <LINK> <LINK> P.S. the right link is <LINK>..... @exohugh Assuming at least 100% efficiency, which is not expected by models?",https://arxiv.org/abs/1809.07374,"When and how planets form in protoplanetary disks is still a topic of discussion. Exoplanet detection surveys and protoplanetary disk surveys are now providing results that allow us to have new insights. We collect the masses of confirmed exoplanets and compare their dependence with stellar mass with the same dependence for protoplanetary disk masses measured in ~1-3 Myr old star-forming regions. The latter are recalculated by us using the new estimates of their distances derived from Gaia DR2 parallaxes. We note that single and multiple exoplanetary systems form two different populations, probably pointing to a different formation mechanism for massive giant planets around very low mass stars. While expecting that the mass in exoplanetary systems is much lower than the measured disk masses, we instead find that exoplanetary systems masses are comparable or higher than the most massive disks. This same result is found also by converting the measured planet masses into heavy-element content (core masses for the giant planets and full masses for the super-Earth systems) and by comparing this value with the disk dust masses. Unless disk dust masses are heavily underestimated, this is a big conundrum. An extremely efficient recycling of dust particles in the disk cannot solve this conundrum. This implies that either the cores of planets have formed very rapidly (<0.1-1 Myr) and large amount of gas is expelled on the same timescales from the disk, or that disks are continuously replenished of fresh planet-forming material from the environment. These hypotheses can be tested by measuring disk masses in even younger targets and by better understanding if and how the disks are replenished by their surroundings. ","Why do protoplanetary disks appear not massive enough to form the known