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Similar to the Asteroid Belt and Kuiper Belt, astronomers using the ALMA Observatory in Chile – part of the European Southern Observatory – have found rings of cold dust orbiting the closest star to the Solar System, Proxima Centauri (or Proxima for short).

Proxima – a red dwarf star – is just over four lightyears away from the Sun in the constellation of Centaurus. In 2016, astronomers found an Earth-like planet called Proxima b orbiting the star. This new research might reveal clues to the existence of more planets.

ALMA, which stands for Atacama Large Millimeter/submillimeter Array, detected a glow coming from cold dust in the inner belt, thought to have a temperature of about -230 degrees Celsius; about as cold as the Kuiper Belt. Researchers using the ALMA data think they’ve also detected a feint glow from an outer, even colder belt. 

These belts are thought to be composed of ice and rock, and are located at distances of a few hundred million kilometres from Proxima and about ten times further out respectively. These vast rings contain particles as small as tiny dust grains of a few millimetres across, up to the size of asteroids, as large as a few kilometres in diameter. 

Guillem Anglada, from the Instituto de Astrofísica de Andalucía (CSIC) in Spain, is the lead author of the new study, he said: “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.”

This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope.

Dust belts, like the ones around the Sun, are thought to be the debris left over from the formation of a planetary system, so the ones around Proxima might be a clue to the existence of planets yet to be discovered.

Guillem went on to say: “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. Further study may also provide information that might point to the locations of as yet unidentified additional planets.”

There are plans afoot to send a microprobe to the Proxima system, propelled by laser-driven sails. Called the Starshot project, the mission will result in direct exploration of the planets and belts around our stellar neighbour. But to get there successfully, we’ll need to navigate through these giant belts, so we’ll need to find out as much as we can about the dust environment before we set off.

Pedro Amado, also from CSIC, added: “These first results show that ALMA can detect dust structures orbiting around Proxima. Further observations will give us a more detailed picture of Proxima’s planetary system. What we are seeing now is just the appetiser compared to what is coming!”