Astronomers observe an elusive second-generation disk around a dwarf star

Around these stars, the most common ones in our galaxies, it is rather common to find terrestrial planets. This research sheds light on the early stages of the evolution of circumstellar disks around such stars.

An international team of astronomers detected a circumstellar disk, which is thought to be a debris disk around a young low-mass star, something that is not very common. Johan Olofsson, associated researcher from the Millenium Nucleus of Planet Formation, participated in the study  as the second author.

The detection of disks around these red stars, known by astronomers as stars of spectral class M, is relevant because it allows the exploration of the possible link between their occurrence and the presence of terrestrial planets in the system, which are known to be common around M type stars.

“We do not know many debris disks (composed of Pluto-sized bodies, small dust grains, and devoid of gas) around M type stars, which is surprising, because we do know that these stars have gas-rich disks just after they have been formed. This is the reason why this work is interesting, because we can test the impact of stellar winds and other interactions of the central star with the disk itself, for instance.”, explains Olofsson, who is also a researcher from the Institute of Physics and Astronomy at Universidad de Valparaíso, and director of the Max Planck Tandem Group (agreement between the Max Plack Institute for Astronomy, in Heidelberg, Germany, and Universidad de Valparaíso).

The study was carried out using images obtained with SPHERE, an instrument installed at the Very Large Telescope (VLT), from ESO, in Chile. SPHERE allows to suppress the light from the central star, using a coronagraph, so that it is possible to get a better view (contrast) of the regions that surround them. Those observations were obtained as part of the large survey SHINE, dedicated to the search of exoplanets.

The central star, GSC 07396-00759, is part of a system of three stars. This multiple system is actually composed of a pair of two stars plus GSC 07396-00759, which orbits around those two stars but at a wide separation. Olofsson explains that the disk surrounding the central binary system is more massive and still has a lot of gas. “Both disks should have more or less the same age, since everything points out that they formed at the same time. This means that there had to be something different in the evolution of each disk.”, comments the astronomer.

The disk around GSC 07396-00759 is edge-on with respect to an observer on Earth (i.e., it is seen from the side). This orientation of the disk makes its detection more favorable despite its faintness, mostly because of the way the images are post-processed and combined altogether.

After this publication, Olofsson expects to do follow-up observations using ALMA. “Among other things, we want to have a better idea of the dust mass in the disk, and, potentially, to search for gas”, he says.

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Image: ESO/E. Sissa et al.

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