Webb Space Telescope spots asteroid belt around star 25 light-years away

New images from the James Webb Space Telescope (JWST) show Fomalhaut, a star approximately 25 light-years from Earth, has an asteroid belt that may be gravitationally shepherded by unseen planets.

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Fomalhaut is roughly 440 million years old making it a relatively young star (our Sun is about five billion years old). This means the system could still be in its planet-forming phase.

Orange dot star with orange ring of dust and debris against black
This 2017 image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows Fomalhaut (centre) encircled by its outer ring of dusty debris. Credit: ALMA (ESO/NAOJ/NRAO)/L. Matrà/M. A. MacGregor.

The system was already known to have a ring of debris around it. This debris disk of dust, pebbles and other remnants of collisions, was discovered in the early 1980s and is considered analogous to the Kuiper belt in our own solar system. The Kuiper belt is a doughnut-shaped ring of icy objects just beyond the orbit of Neptune between 30- and 55-times Earth’s orbit from the Sun.

Now, astronomers have used data from JWST’s Mid-Infrared Instrument to reveal a previously unknown, narrow intermediate belt analogous to the asteroid belt between Mars and Jupiter in our own solar system.

The new belt appears to be influenced by the gravitational fields of unseen planets. In 2008, the Hubble Space Telescope found a planet orbiting the star. But the new inner asteroid belt is misaligned compared to the outer debris disk, suggesting an active planetary system is shepherding the asteroid belt into shape.

Astronomers suggest that the intermediate belt may have been the origin of a previously known dust cloud produced by a collision.

Webb’s images also show a large dust cloud within the outer ring, potentially caused by another collision, which has been dubbed the “Great Dust Cloud.”

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Fomalhaut is the 18th brightest star in the night sky and sits in a region of the sky otherwise lacking in bright stars. The JWST’s highly sensitive instruments have revealed complex features in the star system previously unseen and shows a highly dynamic stellar system.

The study is published in Nature Astronomy.

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