Figure: three belts of debris and dust around Fomalhaut. The two inner belts were first seen by the James Webb Telescope. Image source: NASA, ESA, CSA, A. Gáspár, A. Pagan.
In one of the brightest stars in the southern sky, the star Fomalhaut, the James Webb Telescope found two inner belts of debris and dust, in addition to the long-known outer belt. This may indicate that it has a complex planetary system. The results of the observations are published as a preprint.
The constellation of the Southern Pisces Fomalhaut is located relatively close to the solar system – at a distance of 25 light years. It is a relatively young star several hundred million years old. Back in the 1980s, astronomers noticed a ring-shaped formation around it, apparently consisting of asteroids, comets, debris and dust. This ring, probably analogous to the solar system's Kuiper belt, lies at a distance from Fomalhaut about twice the size of the Kuiper belt. (The Kuiper belt is a multitude of small bodies in the solar system beyond the orbit of Neptune up to a distance of 55 astronomical units from the Sun.) At one time it seemed to astronomers that they were observing something like a planet near Fomalhaut, but this discovery was subsequently not confirmed: “ planet" turned out to be , apparently, a cloud of dust from the collision of bodies in orbit around the star.
Now the James Webb Telescope, thanks to its work in the longer infrared range, has made it possible to observe two other belts of debris and dust around Fomalhaut: the disk immediately surrounding the star and the intermediate ring (located between the disk and the outer ring). They were not visible in previous images of the vicinity of Fomalhaut, which were made by the Hubble telescope and ground-based observatories. Belts of debris and dust were heated enough by the star so that their thermal radiation was picked up by James Webb. The belts are attributed to the so-called residual disk of the star: it is assumed that the debris and dust are formed by the collisions of small bodies, such as asteroids or comets, left over from the formation of the planetary system. Dust settles on the star over time, so more and more collisions between debris must occur in order to maintain the dust cloud in a stable state. By the way, "James Webb" directly discerned the consequences of one of the major impacts in the outer belt – it looks like a round cloud of dust.
Fomalhaut's "space construction debris" belts are more complex than the asteroid belt or the Kuiper belt in the solar system. The complex structure of the residual Fomalhaut disk suggests that the star may have an interesting planetary system. Planets can move along the edges of the belts, which “clear” the debris from their orbit. The mystery remains that so far these planets have not been detected by observation.
The authors of the discovery call the Fomalhaut residual disk "the archetype of the residual disk in our galaxy." These remnant disks are made up of the same components found in our solar system. Therefore, the study of a young planetary system at this stage of its evolution will help us understand how the solar system could have been arranged at an early stage of development.
