Free Astronomy Magazine July-August 2018

46 JULY-AUGUST 2018 SPACE CHRONICLES T his SPHERE observation is the discovery of an edge- on disc around the star GSC 07396-00759, which is a mem- ber of a multiple star system included in the DARTTS-S sample. Oddly, this new disc appears to be more evolved than the gas-rich disc around the T Tauri star in the same system, although they are the same age. The disc ex- tends from the lower-left to the upper-right and the cen- tral grey region shows where the star was masked out. [ESO/E. Sissa et al.] Another new SPHERE obser- vation is the discovery of an edge-on disc around the star GSC 07396-00759, found by the SHINE (SpHere INfrared survey for Exoplanets) survey. This red star is a member of a multiple star system also in- cluded in the DARTTS-S sam- ple but, oddly, this new disc appears to be more evolved than the gas-rich disc around the T Tauri star in the same system, although they are the same age. This puzzling difference in the evolutionary timescales of discs around two stars of the same age is another reason why as- tronomers are keen to find out more about discs and their characteristics. Astronomers have used SPHERE to obtain many other impressive im- ages, as well as for other studies in- cluding the interaction of a planet with a disc, the orbital motions within a system, and the time evolu- tion of a disc. The new results from SPHERE, along with data from other telescopes such as ALMA, are revolutionising astronomers’ understanding of the environments around young stars and the complex mechanisms of planetary formation. nearby stars using direct imaging. But the instrument is also one of the best tools in existence to obtain im- ages of the discs around young stars — regions where planets may be forming. Studying such discs is criti- cal to investigating the link between disc properties and the formation and presence of planets. Many of the young stars shown here come from a new study of T Tauri stars, a class of stars that are very young (less than 10 million years old) and vary in brightness. The discs around these stars contain gas, dust, and planetesimals — the building blocks of planets and the progeni- tors of planetary systems. These im- ages also show what our own Solar System may have looked like in the early stages of its formation, more than four billion years ago. Most of the images presented were ob- tained as part of the DARTTS-S (Discs ARound T Tauri Stars with SPHERE) survey. The distances of the targets ranged from 230 to 550 light-years away from Earth. For comparison, the Milky Way is roughly 100000 light-years across, so these stars are, relatively speaking, very close to Earth. But even at this distance, it is very challenging to obtain good im- ages of the faint reflected light from discs, since they are outshone by the dazzling light of their parent stars. !