20 Ring Worlds

image credit: Credit: ALMA (ESO/NAOJ/NRAO), S. Andrews et al. In a team of 17 scientists lead by Sean Andrews, we carried out the Disk Substructures at High Spatial Resolution Project, or DSHARP in short. This consists of over 60 hours of ALMA observations for 20 planet forming disks designed to study the occurrence, forms, locations, sizes, and other properties of structures in the disk material and how they might be related to the planet formation process.

We found that rings are everywhere, while spirals and asymmetries are sometimes present but rare. The positions of the rings show no correlation with the stellar brightness, which basically rules out that condensation fronts are responsible for the rings. Together with the other recent ALMA result (see three baby planets detected) this seems to indicate the planets form abundantly and faster than expected. At the same time, these results also open new questions, for example: why do all rings seem to be equally transparent? When do these structures (or planets) form, are they already present in much younger disks? What to disks in other star forming regions, that are less massive look like? We still have so much to learn ... ćA; You can read more about this

Three baby planets detected

image credit: Credit: NRAO/AUI/NSF; S. Dagnello In Rich Teagues paper on HD163296 we used the ALMA observatory to hunt for baby planets in their natal environment, the planet forming disks. We use the Doppler effect to measure the gas rotation velocity with unprecedented precision of only a few meters per second. Keep in mind that the disk is about 300 light years away and rotates at speeds of a few kilometers per second! Planets forming inside those disks perturb the gas and cause it to rotate slightly faster or slower. The detected rotation curves are a perfect match to predictions from planet-disk interaction, as coauthor Jaehan Bae carries out. This is good evidence that indeed planets of about Jupiter mass have already formed in this particular disk around the young star HD163296. This is quite surprising, as astronomers have no idea how these massive planets formed so far away from their star (they are more than 80 times farther away from their star than the earth is from the sun). Next, we will apply this method to other disks to see if all the dust rings we see are caused by planets. You can read more about this