James Webb telescope makes unusual discovery – three asteroid belts around a star

The young and bright star Fomalhaut is 25 light-years from Earth – a stone’s throw away on a cosmic scale. As early as 1983, astronomers discovered a ring of dust around the star reminiscent of the Kuiper belt in our solar system. The Kuiper Belt extends beyond Neptune’s orbit and contains tens of thousands of objects more than 100 kilometers in diameter. A large portion of the comets that make their way to the inner solar system come from this region.

Now a US research team from the University of Arizona has once again targeted the hot dust ring around Fomalhaut, which is about twice as wide as the Kuiper belt – this time with the currently most powerful space telescope, the James Webb telescope. It should give them a more detailed view of the dust belt. And they got more than they bargained for: Images through the telescope’s powerful Mid-Infrared Instrument (Miri) revealed that Fomalhaut has not one but three asteroid belts.

This result, now published in the journal Nature Astronomy, came as a surprise, as the dust ring around Fomalhaut had already been studied with the Hubble and Herschel space telescopes and with the Atacama Large Millimeter/submillimeter Array (ALMA). in the Chilean Andes. Those telescopes had provided clear images of the outer asteroid belt, but neither had seen the star’s two inner dust rings.

“What really sets Webb apart is that we can physically resolve the thermal glow of dust in these inner regions. So you can see inner tubes that we couldn’t see before,” explains astronomer Schuyler Wolff, who is part of the research team, in a statement. statement of the European Space Agency ESA. “In total there are three nested bands that extend to a distance of 23 billion kilometers from the star – that is 150 times the distance from the Earth to the Sun,” writes ESA.

The discovery is sensational because the three asteroid belts were probably formed by the influence of several planets moving through the dust – invisible at first. This is indicated by the clearly recognizable gaps between the individual bands. “The asteroid belts around Fomalhaut are kind of a mystery: where are the planets?” explains astronomer Georg Rieke, co-author of the study. “I don’t think it’s far-fetched to say there’s probably a really interesting planetary system around the star.”

Schuyler Wolff agrees. “These structures are very exciting because every time an astronomer sees a hole and rings in a dust disk, he says, ‘There could be a planet hiding there and forming the rings.'”

The dust rings around Fomalhaut are not so-called protoplanetary disks, because they are often found around young stars, where the matter eventually clumps together to form planets and asteroids. However, Fomalhaut has already passed that stage – the dust rings discovered around the star are actually debris disks formed when smaller celestial objects, such as asteroids, collide and are pulverized in the process.

In the outer asteroid belt, the astronomers found another object that had previously gone unnoticed: it is a large cloud of dust that could be the result of a collision between two icy celestial bodies.

An object was already discovered in 2008, but it revolves around Fomalhaut within the dust ring. Initially, astronomers assumed it was a larger exoplanet called Fomalhaut b. However, the object has not been seen since 2014. Newer theories therefore assume that it is also a dust cloud created by the collision between two smaller bodies. Fomalhaut b has therefore been removed from the list of exoplanets again – and the star is currently officially planetless again.

The study’s lead author, András Gáspár of the University of Arizona, hopes for even more accurate images of the dust belts: “Looking at the patterns in these rings, we can make a small sketch of what a planetary system should look like. like — if we have a picture sharp enough to see the suspected planets.” (i.e)