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Astronomers used NASA’s James Webb Space Telescope to image the warm dust around a nearby young star, Fomalhaut, in order to study the first asteroid belt seen outside our solar system in infrared light. But to their surprise, the dusty structures are much more complex than the Kuiper and Kuiper dust belts in our solar system. Overall, there are three overlapping belts that extend up to 14 billion miles (23 billion km) from the star; This is a distance of 150 times the distance between the Earth and the Sun. The outer belt is about twice the size of our solar system’s Kuiper belt, made up of small bodies and cold dust beyond Neptune. The inner girdles – never before seen – were revealed by Webb for the first time.
The belts surround the hot young star, which is visible to the naked eye as the brightest star in the southern constellation Piscis Austrinus. Dusty belts are debris from the collision of larger bodies, similar to asteroids and comets, and are often described as “debris discs”. “I would characterize Fomalhaut as the archetype of debris disks found elsewhere in our galaxy, because they contain similar components to those found in our planetary system,” said András Gáspár of the University of Arizona in Tucson and lead author of the new paper. describing these results. “By looking at the patterns in these rings, we can actually begin to draw a small outline of what a planetary system should look like — if we can actually take a picture deep enough to see the suspect planets.”
The Hubble Space Telescope and Herschel Space Observatory, as well as the Atacama Large Millimeter/Submillimeter Array (ALMA), have previously captured sharp images of the outer belt. However, none of them found any internal structure of it. The inner belts were first resolved by Webb in infrared light. “Webb really excels in our ability to physically resolve the heat glow from the dust in those inner regions. So you can see the inner belts that we haven’t been able to see before,” said Schuyler Wolf, another member of the university team. Arizona.
Hubble, ALMA and Webb are uniting labels to compile a comprehensive view of debris disks around a number of stars. “Using Hubble and ALMA, we’ve been able to image a range of Kuiper belt isotopes, and we’ve learned a lot about how outer disks form and evolve,” said Wolf. “But we need Webb to allow us to image a dozen or so asteroid belts elsewhere. We can learn as much about the warm inner regions of these disks as Hubble and ALMA have taught us about the cooler outer regions.”
These belts are likely sculpted by the gravitational forces produced by the unseen planets. Likewise, within our solar system, the asteroid belt is surrounded by Jupiter, the inner edge of the Kuiper belt is carved by Neptune, and the outer edge can be grazed by bodies as yet unseen. As Webb pictures more systems, we’ll learn about the configurations of their planets.
Fomalhaut’s dust ring was discovered in 1983 in observations made by NASA’s Infrared Astronomy Satellite (IRAS). The ring’s existence has also been inferred from earlier, longer-wavelength observations using submillimeter telescopes on Mauna Kea, Hawaii, NASA’s Spitzer Space Telescope, and Caltech’s Submillimeter Observatory.
“The belts around Fomalhaut are a kind of mystery novel: Where are the planets?” said George Rick, another team member and US science lead for the Webb Medium Infrared Instrument (MIRI), who made the observations. “I think it’s not too big of a leap to say that there is likely to be a really interesting planetary system around the star.”
“We certainly didn’t expect the more complex structure with the second intermediate belt and then the wider asteroid belt,” Wolf added. “This structure is so exciting because anytime an astronomer sees a gap and rings in a disk, they say, ‘There could be an embedded planet that makes up the rings!'”
Webb also imaged what Gáspár calls the “great dust cloud,” which may be evidence of a collision in the outer ring between two protoplanetary bodies. This is a different feature from a suspected planet first seen within the outer ring by Hubble in 2008. Subsequent Hubble observations showed that by 2014 the object had disappeared. A plausible explanation is that, like the previous one, this newly discovered feature is an expanding cloud of very fine dust particles from two icy bodies colliding with each other.
The idea of a protoplanetary disk around a star dates back to the late 18th century when astronomers Immanuel Kant and Pierre Simon Laplace developed a theory that the sun and planets formed from a rotating gas cloud that collapsed and flattened due to gravity. Debris disks develop later, after the formation of planets and the diffusion of primordial gas into the systems. They showed that small bodies like asteroids collide catastrophically and their surfaces shatter into huge clouds of dust and other debris. Observations of its dust provide unique clues to the structure of the exoplanet system, which range from Earth-sized planets to even asteroids, which are much smaller than seen individually.
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