International team of astronomers explains the cause of the mysterious shape of the disk surrounding a young star

Two researchers from the Millenium Nucleus of Planet Formation participated in the study. The workwas carried out using numerical simulations.

A group of international astronomers, among which Nicolás Cuello, young researcher of the Millenium Nucleus of Planet Formation, and Jorge Cuadra, Associated researcher of the centre, stand out, concluded that the mysterious shape of the disk that surrounds the star HD142527, is caused by the influence of a secondary star. The research was published in the prestigious journal Monthly Notices of the Royal Astronomical Society.

The image shows the distribution of the gaseous disk around the binary stellar system in the center.

Protoplanetary disks are systems where planets form around young stars. Usually, they are modeled as axisymmmetric structures with a wheel shape. In other words, they are equal in all angular directions, with a star in the centre. However, various physical processes can operate inside the disk and break this symmetry. This can give rise to spirals, serpentines, shadows and bananas, as it is the case in this study.

“During these last years we have noticed that a great fraction of disks suffer from gravitational perturbations caused by planets and other stars. This means that we have to consider models that are more complex, with several stars and/or planets”, says Nicolás Cuello, second author of the study.

In the case of the disk around the binary system HD142527, the astronomers collected all the information obtained during the last 12 years from different telescopes (ALMA, VLT, ATCA). Cuello explains that there was a great variety of structures, and, in particular, a concentration of dust with a banana shape, which was difficult to explain and constituted one of the open questions in the field. They knew that there was a low-mass star hidden inside the central cavity of the disk, but its orbit around the central star was almost completely unknown to them.

“We thought about trying different types of orbits and get out of the classic paradigms a little bit”. We considered oval-shaped inclined orbits inside the cavity, instead of orbits on the plane of the disk, and we stumbled across the solution. The dynamical effects from the binary generated a big banana of dust in the disk, and therefore, the secondary star was responsible for it!”, comments Cuello, who is also a post-doctoral researcher at the Institute of Astrophysics, in Universidad Católica.

Future work

After this research, the authors are exploring other “exotic” disks, where there are also big central cavities and a lot of structure. “We are particularly interested in systems where the secondary star has not been detected yet. In other words, we are hunting stars that hide inside cavities of protoplanetary disks. It is likely that they are much more common than we thought, and that this has important implications for planetary formation”, ends Cuello.

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