Five exocomets discovered around another star

Five exocomets discovered around another star

Science

A team of Ukrainian astronomers announces the discovery of five new exocomets around a nearby star. Their study could shed light on the history of our own solar system. Details of this work are published in the journal Astronomy & Astrophysics.

Put into orbit in April 2018, TESS (abbreviation of Transiting Exoplanet Survey Satellite) had the heavy responsibility of succeeding the Kepler telescope. Like its predecessor, TESS uses the transit method to carry out its mission. This approach consists in detecting weak and regular drops of stellar luminosity which generally testify to the repeated passage of planets between the observer (TESS) and the host star. However, this is not always the case.

Five new exocomets

In a study, astronomers from the National Academy of Sciences of Ukraine, Kyiv, analyzed several dips in brightness recorded in the spectrum of the star Beta Pictoris, about 65 light-years from Earth . According to their examination, these would be the work not of planets, but of comets. They would be five in number. The latter evolving around a star other than the Sun, astronomers therefore speak of exocomets.

The researchers were able to make the distinction here insofar as the transits of comets are steeper and more unbalanced than those of exoplanets, in part because of their long tails.

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This is not the first time that exocomets have been observed around this star. The first detection with TESS indeed took place in 2019. Previous studies have also deduced that Beta Pic actually offers two different groups of exocomets with different properties. However, the discovery of new objects of this type is always very interesting.

Indeed, within our system, which itself is full of comets, these objects are studied as relics of the past. They provide clues to the chemistry of the formation of the Earth and its neighboring planets. Comets are also believed to have played a key role in bringing life to our planet by delivering water and other essential compounds. So, if the history of our own Solar System is so dependent on comets, how could we hope to understand other planetary systems without knowing theirs?

A look back

The discovery is all the more interesting as Beta Pictoris is a much younger star than the Sun. It is indeed only ten to forty million years old (compared to 4.6 billion years for the Sun), which makes it a useful snapshot to better understand the youth of a planetary system. We also know that a giant planet eleven times larger than Jupiter and an enormous disc of dust nearly forty billion kilometers in diameter surround this young star.

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These discs, where the objects (planets, dwarf planets, comets, etc.) that will then revolve around Beta Pic are formed, are often chaotic and violent places. For this reason, comets can still approach their stars much more often, allowing their detection. Then, things tend to calm down and comets are very often relegated to the icy confines of their system.

So if there’s one takeaway from this discovery, it’s that exocomets definitely seem common, at least around a star like Beta Peak. Scientists therefore expect TESS to discover many more in the future. The James Webb Telescope, which is due to begin its first observations this summer, could also help astronomers.