Discovery of 30 exocomets in a young planetary system

The star β Pictoris harbors a young planetary system of about 20 million years old. This planetary system is characterized by the presence of a gaseous and dusty debris disk, at least two massive planets, and many minor bodies. These were detected as early as 1987. For more than thirty years, exocomets transiting the star have been detected using spectroscopy, probing the gaseous part of the cometary comas and tails.

The star β Pictoris has fascinated astronomers because it enables them to observe a planetary system in the process of formation.

These were the first comets ever observed around a star other than the Sun.

An international research team headed by Alain Lecavelier des Etangs, CNRS researcher at the Institut d’Astrophysique de Paris (CNRS/Sorbonne Université), has discovered 30 such exocomets and determined the size of their nuclei, which vary between 3 and 14 kilometres in diameter.

Their findings were published in Scientific Reports on April 28, 2022. These findings are the outcome of 156 days of observation of the β Pictoris system using NASA’s Transiting Exoplanet Survey Satellite (TESS).

First-ever system detected outside our Solar System

The scientists were also able to estimate the size distribution of the objects, i.e., the proportion of small comets to large ones. This is the first time this distribution has been measured outside our Solar System, and it is strikingly similar to that of comets orbiting the Sun.

It shows that, just like the comets of the Solar System, the exocomets of β Pictoris were shaped by a series of collisions and breakups.

“The measured absorption depth distribution is the result of the distribution of several parameters for each individual comet, e.g., the orbital parameters, cometary activity, composition, size, etc.” Study mentions.

This work sheds new light on the origin and evolution of comets in planetary systems. Since a part of Earth’s water probably originated in comets, scientists are seeking to understand their impact on the characteristics of planets.

The observed distribution of exocomets in the young planetary system of β Pic is strikingly similar to the distribution observed in the Solar system.

Other upcoming observations, in particular with the Hubble and James Webb space telescopes, should enable scientists to find out more in the future.

Journal Reference

1. Alain Lecavelier des Etangs, Lucie Cros, Guillaume Hébrard, Eder Martioli, Marc Duquesnoy, Matthew A. Kenworthy, Flavien Kiefer, Sylvestre Lacour, Anne-Marie Lagrange, Nadège Meunier & Alfred Vidal-Madjar. Exocomets size distribution in the β Pictoris planetary system. Scientific Reports 12, 5855 (2022). DOI: 10.1038/s41598-022-09021-2