Astronomers have spotted an asteroid belt and an enormous dust cloud around one of the nearest and brightest stars in the night sky.
Known as Fomalhaut, the star lies 25 light years from Earth in the constellation of Piscis Austrinus, or the southern fish. Though best seen from the southern hemisphere, it can be viewed from a large part of the northern hemisphere, especially in the autumn. Its brightness and position mean it is still used for navigation.
Previous observations by the Hubble space telescope and other instruments showed the 440m-year-old Fomalhaut to be surrounded by dust and debris, but the images gave only a partial picture of the cosmic material circling the young star.
Now, high-resolution images from the James Webb space telescope have revealed the star’s surroundings in unprecedented detail. Beyond an extensive inner asteroid belt that swirls around the star is a second narrower ring of rock and rubble.
“What we see is the dust produced in collisions between planetesimals, which themselves are the long forgotten remnants of the formation of the planetary system itself,” said András Gáspár, lead author on the study at the University of Arizona.
Further out still from Fomalhaut is an outer ring of debris that resembles the solar system’s Kuiper belt, home to Pluto and the other dwarf planets, Eris, Haumea, and Makemake. It was in this outer ring that the astronomers spotted what they call the great dust cloud, which they suspect was produced when two space rocks more than 400 miles wide slammed into one another.
The scientists identified the new features in images taken by the mid-infrared instrument onboard the James Webb space telescope. The three nested belts and the gaps between them suggest that unseen planets are circling Fomalhaut and shaping the star system through their gravitational fields. “Planets as low in mass as Neptune are sufficient to carve the inner belts,” the authors write in Nature Astronomy.
