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Cool Dust Discovered Around Proxima Centauri.

TANTALIZING OBSERVATIONS reveal a dusty ring and additional dust structures in the Proxima Centauri system--the one that hosts the nearest exoplanet to Earth (S&T: Dec. 2016, p. 10).

A team of astronomers led by Guillem Anglada (Institute of Astrophysics of Andaluda, Spain; not to be confused with Guillem Anglada-Escude, Proxima Cen b's discoverer) pointed the Atacama Large Millimeter/submillimeter Array (ALMA) at Proxima Centauri for more than 20 hours, revealing the presence of a dusty ring around the star. The planet Proxima Cen b circles its star at a distance of just 7V.2 million km, or 0.05 astronomical unit (for reference, Mercury orbits the Sun at 0.39 a.u.). The dusty ring lies well beyond that, extending from 1 to 4 a.u. The results will appear in Astrophysical Journal Letters.

Like our solar system's Kuiper Belt, the Proxima belt contains fine grains with similar average temperature and total mass. The Kuiper Belt might be debris leftover from planet formation, and the existence of a dusty belt around Proxima Centauri could mean more planets wander around this dim star.

In addition to the belt, the team notes hints of other dusty features. The most speculative of these, but also the most intriguing, is the possible discovery of an asymmetry in the dust belt, which could be due to a planet embedded within the dust. The team also found hints of a second, colder belt of dust about 30 a.u. from the star, as well as a possible shroud of warmer dust closer to the star (but still outside Proxima Cen b's orbit), at roughly 0.4 a.u. More observations are needed to confirm these additional features.

Caption: An artist visualizes the inner and outer dust belts around Proxima Centauri.

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Title Annotation:EXOPLANETS
Author:Bochanski, John
Publication:Sky & Telescope
Date:Jan 10, 2018
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