In orbit of distant star
Researchers discover 30 tail stars
April 28, 2022, 4:50 p.m
Near the star Beta Pictoris, researchers are encountering dozens of exocomets. Using a special technique, they can prove their size for the first time. From this, the scientists derive parallels to the formation of our solar system.
A team of researchers from France, Brazil and the Netherlands has detected as many as 30 comets near the star Beta Pictoris, 63 light-years away, using the US space telescope TESS. For the first time, the astronomers were able to analyze the size distribution of the tail stars of another star. The exocomets, which are between 3 and 14 kilometers in size, show a distribution similar to that in our solar system – and should therefore have arisen in a similar way, write the scientists in the journal “Scientific Reports”.
Beta Pictoris is a young star still surrounded by a disk of gas and dust where planets may still be forming. Astronomers have discovered two large planets in the system so far – and also the traces of comets. ‘Comets have been detected passing in front of the star as seen from Earth for 30 years,’ explain Alain Lecavalier des Etangs of Sorbonne University in France and his colleagues.
The comets give themselves away because their tails of gas and dust on these transits swallow up starlight at certain wavelengths – and this absorption then shows up as dark lines in Beta Pictoris’ spectrum. The scientists have now used a different observation method: With NASA’s TESS (Transiting Exoplanet Survey Satellite) telescope, they have monitored the brightness of the star with high accuracy for 156 days.
Brightness allows conclusions to be drawn about size
TESS is used to search for planets near other stars: If such a planet passes in front of the star as seen from Earth, it weakens the starlight slightly and thus reveals itself. The transit of a comet with its large tail also leads to such an attenuation – albeit less. The researchers were able to identify a total of 30 such comet transits in the TESS data. Based on the strength of the weakening, they were also able to deduce the size of the comet.
This made it possible for the first time to determine the size distribution of comets near another star. “16 of the comets have a diameter of three to four kilometers – but only four are between six and eight kilometers and only one is between eight and ten kilometers in size,” the scientists report. Small comets are therefore much more common in Beta Pictoris than large ones. The distribution is thus similar to that in our solar system.
For the researchers, this is an indication that the formation and development of the comets at Beta Pictoris was similar to that in our planetary system. Such a distribution of the sizes occurs when the celestial bodies often collide with each other and break up – but sometimes also merge again to form larger bodies. This is an important finding for the astronomers, because comets probably brought a large part of the water into the inner solar system and thus also onto Earth. Such processes should therefore also take place in other planetary systems in a very similar way.