Exocomet swarm discovered around the young star Beta Pictoris

A French team has just discovered 30 exocomets around the young star Beta Pictoris. The discovery of these balls of ice and dust makes it possible to learn more about the formation of planets.

Artist’s rendering of exocomets orbiting the star Beta Pictoris © L.Calçada / ESO

The first exocomets were discovered in 1987. These are comets orbiting stars other than our sun. Beta Pictoris is particularly studied because it is a young star that is still in the process of formation. A few weeks ago, a team of Ukrainian astronomers confirmed the presence of eight exocomets around this star. In the journal Scientific Reports, an international team led by Alain Lecavelier des Étangs, CNRS researcher at the Institut d’Astrophysique de Paris, blew up the counter and announces having discovered 30 exocomets around the same star very shiny. A real breakthrough Achieved thanks to previous work of the scientist This result is not surprising, since the scientist was able to benefit from his work 25 years ago, when he predicted the theoretical variation of the star’s luminosity at the time of the passage of exocomets. A bird’s beak shape, although he prefers to say “in a rounded triangle”.

The data comes from NASA’s TESS space telescope. The spacecraft observed the beta star Pictoris for 156 days in a row. Thirty exocomets that make it possible to create statistics, explains Alain Cavelier of Les Etangs: “this makes it possible to obtain a distribution of these objects, ie to know how many small and how many large comets there are. The real scientific result is that we’ve got a distribution factor, and it’s exactly the one observed in our solar system“, explains the researcher enthusiastically. Apparently, his team found 10 times more small comets than large ones. This is the first time that the distribution has been measured in an extrasolar system.

Exocomets, remnants of planet formation

The size of the comet nuclei with a diameter of 3 to 14 km could be calculated from their dust tail. But more than size, distribution matters. It allows to confirm that these comets were formed thanks to a cascade of collisions that led to their fragmentation.

Comets are born at the same time as planets but are somehow Scrap from the manufacturing phase. “After all, it is the building blocks from which the planets were made. We can say that there is a bit of residue like when we build a cathedral of cut stones. There are still unused rocks and exocomets are those rock piles that were not used during planet formation. They are therefore a tracer of what was happening at the time of planet formation.” explains Alain Cavelier des Étangs.

Because Beta Pictoris is only 20 million years old, it’s a young star.”straight out of the maternity ward“, he adds. Seeing the state of these comets only at the end of the process is extremely interesting, in his opinion. All the more interesting because in our solar system the big question is still unresolved about the role of comets Did they contribute to the Enrich atmosphere with certain elements? Did they bring the water as we imagine? The investigation is ongoing and more observations are needed to move forward. Plato, the European Space Agency’s future telescope announced for 2026, is said to make it possible to traverse a course thanks to its precision. The recently launched James Webb telescope will also be used.

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