Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have detected dust belts around Proxima Centauri, the star closest to our Sun. Full details of the discovery will be published in the Astrophysical Journal Letters (arXiv.org preprint).
This artist’s impression shows how the newly-discovered dust belts around Proxima Centauri may look. This sketch is not to scale — to make Proxima b clearly visible it has been shown further from the star and larger than it is in reality. Image credit: M. Kornmesser / ESO.
Proxima Centauri is a red dwarf star only 4.23 light-years away in the constellation Centaurus. It is not visible to the naked eye and lies near to the much brighter pair, Alpha Centauri AB.
The star is known to host at least one exoplanet — the Earth-mass world Proxima b — in a temperate orbit.
But there is more to this system than just a single planet.
The new ALMA observations reveal the glow coming from cold dust in a region between 1 to 4 AU (astronomical units).
This belt has a total mass of about one hundredth of the Earth’s mass is estimated to have a temperature of about minus 230 degrees Celsius (minus 382 degrees Fahrenheit), as cold as that of the Kuiper Belt in the outer Solar System.
“The dust around Proxima Centauri is important because, following the discovery of 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 lead author Dr. Guillem Anglada, from the Instituto de Astrofísica de Andalucía 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 millimeter across, up to asteroid-like bodies many kilometers in diameter.”
The ALMA data also hint at the presence of an extremely cold outer belt around Proxima Centauri.
According to the astronomers, the outer belt is approximately 30 AU from the star and has a temperature of about minus 263 degrees Celsius (minus 441 degrees Fahrenheit).
If confirmed, the nature of this 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 Proxima b, which orbits at just 0.05 AU from the 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,” Dr. Anglada said.
“Further study may also provide information that might point to the locations of as yet unidentified additional planets.”
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Guillem Anglada et al. 2017. ALMA Discovery of Dust Belts around Proxima Centauri. ApJL, in press; arXiv: 1711.00578
