Dust belts around Proxima Centauri: Scientists

By PTI Published on Nov 06, 2017 12:49 PM IST

London: Scientists have detected dust belts around Proxima Centauri, a finding that indicates the presence of an elaborate planetary system hosted by the closest star to the solar system.

New observations by Atacama Large Millimeter Array (ALMA) Observatory in Chile revealed the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun.

The data also hints at the presence of an even cooler outer dust belt and may indicate the presence of a system of planets. These structures are similar to the much larger belts in the solar system and are also expected to be made from particles of rock and ice that failed to form planets.

Proxima Centauri is the closest star to the Sun. It is a faint red dwarf lying just four light-years away in the southern constellation of Centaurus. It is orbited by the Earth-sized temperate world Proxima b, discovered in 2016 and the closest exoplanet to the solar system.

However, there is more to this system than just a single planet. The new ALMA observations reveal emission from clouds of cold cosmic dust surrounding the star.

"The dust around Proxima is important because, following the discovery of the terrestrial planet Proxima b, it's the first indication of the presence of an elaborate planetary system, and not just a single planet, around the star closest to our Sun," said Guillem Anglada, from the Instituto de Astrofisica de Andaluc'a (CSIC) in Spain.

Dust belts are the remains of material that did not form into larger bodies such as planets. The particles of rock and ice in these belts vary in size from the tiniest dust grain, smaller than a millimetre across, up to asteroid-like bodies many kilometres in diameter.

Dust appears to lie in a belt that extends a few hundred million kilometres from Proxima Centauri and has a total mass of about one hundredth of the Earth's mass.

This belt is estimated to have a temperature of about minus 230 degrees Celsius, as cold as that of the Kuiper Belt in the outer solar system.

There are also hints in the ALMA data of another belt of even colder dust about ten times further out. If confirmed, the nature of an outer belt is intriguing, given its very cold environment far from a star that is cooler and fainter than the Sun.

Both belts are much further from Proxima Centauri than the planet Proxima b, which orbits at just four million kilometres from its parent star.

"This result suggests that Proxima Centauri may have a multiple planet system with a rich history of interactions that resulted in the formation of a dust belt," said Anglada, lead author of the study published in the Astrophysical Journal Letters.

Proxima Centauri's planetary system is also particularly interesting because there are plans for future direct exploration of the system with microprobes attached to laser- driven sails