The formation of planets in a binary star system

Most stars form binary systems, in which two stars revolve around a common center. However, models of planet formation, which suggest that planets are born by the slow aggregation of ice and dust particles in the protoplanetary disks around the forming stars, usually consider only isolated stars, such as the Sun. Thus, it is still unknown how planets are born around double stars, in which the gravitational interaction between the two plays an essential role.

Using the Very Large Array (radio astronomical observatory in New Mexico) and the Atacama Large Millimeter/Submillimeter Array (the largest radio telescope in the world), a scientific group led by researchers from the CSIC has studied the binary star SVS 13, still in its embryonic phase, and has provided the best description available to date of a binary system in formation.

“Our results have revealed that each star has a disk of gas and dust around it and that, in addition, a larger disk is forming around both stars”points out Ana Karla Díaz-Rodríguez, leader of the work and researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC) and the ALMA Regional Center of the United Kingdom (UK-ARC).

“This disc shows a spiral structure that is feeding matter to the individual discs, and in all of them, planetary systems could form in the future”, points out the researcher. This is clear evidence of the presence of disks around both stars and of the existence of a common disk in a double system.

The two stars of the binary system SVS 13

The SVS 13 binary system, made up of two stellar embryos with a combined mass similar to that of the Sun, lies relatively close to us, about 980 light-years away in the Perseus molecular cloud. The two stars in the system are very close to each other, with a distance of only about ninety times that between the Earth and the Sun.

The work has made it possible to study the composition of the gas, dust and ionized matter in the system. In addition, almost thirty different molecules have been identified around both protostars, including thirteen complex organic molecules that are precursors of life (seven of them detected for the first time in this system). “This means that when planets begin to form around these two suns, the building blocks of life will be there.”indicates Ana Karla Díaz-Rodríguez.

In the scientific literature, SVS 13 has generated much debate, since some studies consider it to be extremely young and others to be in a somewhat later phase of formation. This new study, probably the most comprehensive of a binary star system in formation, not only sheds light on the nature of the two protostars and their environment, but also provides crucial parameters to test numerical simulations of the early stages of the formation of binary and multiple systems.

A decades-long investigation

The scientific group has used the observations of SVS 13 taken by the Very Large Array for thirty years, along with new data from Atacama Large Millimeter/Submillimeter Arrayand has followed the movement of both stars throughout this period, which has made it possible to infer their orbit, as well as the geometry and orientation of the system, together with several fundamental parameters, such as the mass of the protostars, that of the disks and its temperature.

“At the IAA we started studying this system twenty-five years ago. We were surprised when we discovered that SVS 13 was a binary in radio, because only one star appears in the visible. Normally, stellar embryos are detected in radio, but they only become visible at the end of the gestation process. It was very strange to discover a pair of twin stars where one seemed to have evolved much faster than the other. We designed several experiments to get more details and find out if in a case like this any of the stars could form planets. Now we have seen that they are both very young, and that they can both form planets.”indicates Guillem Anglada, a researcher at the Institute of Astrophysics of Andalusia (IAA-CSIC).

Font: CSIC, DICYT,

Reference article: https://www.dicyt.com/noticias/observan-el-beginning-of-the-gestation-of-planets-in-a-binary-system-of-stars