The star β Pictoris has fascinated astronomers for about thirty years because it allows them to observe a planetary system in full formation. It is composed of at least two young planets, but it also contains comets, detected since 1987. These were the first comets to be found around a star other than the Sun.
Today, the work of an international research team led by Alain Lecavelier des Etangs, CNRS researcher at the Paris Institute of Astrophysics (CNRS/Sorbonne University) [1]. The discovery of 30 of these exocomets and the determination of the size of their nuclei [2] have been made possible. It varies between 3 and 14 kilometers in diameter.
Scientists were also able to estimate the size distribution of these objects, that is to say the proportion of small comets compared to large ones. This is the first time that this distribution has been measured outside the Solar System, and it is surprisingly similar to that of comets in orbit around the Sun. It shows that β Pictoris exocomets, like Solar System comets, have been sculpted by cascades of collisions and fragmentations.
This work sheds new light on the origin and evolution of comets in planetary systems. Since comets are probably the origin of some of the water on Earth, scientists are trying to understand their impact on the physiognomy of planets.
Published in Scientific Reports on April 28, 2022, their results are the result of 156 days of observation of the system with Nasa’s Transiting Exoplanet Survey Satellite (TESS). Other observations to come will allow to know more, in particular with the Hubble or James Webb space telescopes.
[1] Also participating in this research were scientists from the Laboratoire d’études spatiales et d’instrumentation en astrophysique (Observatoire de Paris - PSL /CNRS/Sorbonne University/Université Paris Cité) and from the Institut de planétologie et d’astrophysique de Grenoble (CNRS/UGA)
[2] A comet is formed primarily by a rocky nucleus covered with dust and gas in a solid state. The tail, or hair, of the comet appears only temporarily, when the frozen gases are heated and pass to the gaseous state.