Astronomers discover 30 exocomets “strikingly similar” to space rocks near Earth

"This is the first time that a size distribution was measured in an extrasolar planetary system."
Chris Young
An artist's impression of the exocomets.ESO/L. Calçada

An international team of researchers discovered 30 exocomets and determined the size of their nuclei in a world first, a press statement reveals.

The prefix 'Exo' used before comets denotes the fact that these particular space rocks were found outside of our solar system — much in the same way the 5,000 and counting exoplanets found by NASA are planets that do not orbit our Sun.

"This is the first time that we have an estimate of the size of [any] exocomets' nuclei and the first time that a size distribution was measured in an extrasolar planetary system," Alain Lecavelier des Etangs, CNRS researcher at the Institut d'Astrophysique de Paris and head of a new study on the subject told IE in an interview.

"Moreover, we found that the exocomet size distribution in the β Pictoris planetary system is strikingly similar to the one in our solar system," he explained.

The first-ever size distribution measurement of exocomets

The new batch of exocomets was discovered orbiting the star system β Pictoris, or Beta Pictoris, which astronomers have observed for more than three decades due in large part to the fact it contains a planetary system that is in the process of formation. In 1987, the first-ever exocomets were detected in the star system, located some 63.4 light-years away from Earth.

The new study, headed by Lecavelier des Etangs and published in Scientific Reports, outlines the discovery of 30 new exocomets and also provides the most detailed analysis yet of the interstellar space rocks. Looking at observation data collected over 156 days by NASA's Transiting Exoplanet Survey Satellite (TESS) the team used photometry to take new, high-precision readings.

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"Up until recently, observations of β Pictoris were made only using spectroscopy, probing the gaseous cloud surrounding the cometary nuclei," Lecavelier des Etangs said. "Using high precision photometry, we could probe the dust tail of the comets, as we predicted more than 20 years ago (in 1999). That's why we decided to [focus on] the observations of Beta Pictoris obtained by the NASA TESS observatory from 2018 to 2021." 

The team was able to determine the size of these exocomets' nuclei, showing that they varied between 3 and 14 kilometers in diameter. They were also able to measure the size distribution of the exocomets, a first for comet measurements outside of our solar system.

The researchers explain that the size distribution is very similar to what would be expected within our solar system, showing that the exocomets were very likely shaped by a series of collisions and breakups. "The observed distribution corresponds precisely to the distribution expected in the case of a population of objects that results from a cascade of collisions and fragmentation," as seen nearer Earth, Lecavelier des Etangs explained to IE.

Exocomets provide window into our own solar system

Recent research shows that asteroids and comets may have played a substantial role in the development of life on Earth. This week, scientists announced they had discovered the last two missing nucleobases of DNA within meteorite samples, suggesting that life may have been assisted by space rocks. Last year, an analysis of JAXA's Hayabusa-1 asteroid sample from 2010 highlighted the presence of water and organic matter.

So the new analysis of exocomets could help to sheds new light on the role comets play in the evolution of planetary systems and even in the development of life. If exocomets are so similar to the ones we find in our solar system, could they play a similar role in distant exoplanets?

In the future, new observations from the likes of Hubble and NASA's recently-launched James Webb Space Telescope could provide new insight into the role of the space rocks in a relatively new planetary system.

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