“James Webb Space Telescope Observes Complex Debris Belts Around Nearby Young Star Fomalhaut”

User rating: 5 / 5

Astronomers used NASA’s James Webb Space Telescope to image the warm dust around a nearby young star, Fomalhaut, to study in infrared light the first asteroid belt ever seen outside our solar system. But to their surprise, the dust structures are much more complex than the asteroids and Kuiper belts of our solar system.

In all, there are three nested belts that extend up to 23 billion kilometers from the star; that is 150 times the distance from the Earth to the Sun. The size of the outer belt is about twice the size of our solar system’s Kuiper belt, with small bodies and cold dust beyond Neptune. The inner belts, never seen before, were revealed for the first time by Webb.

The belts encircle the young hot star, visible to the unaided eye as the brightest star in the southern constellation Piscis Austrinus. The dust belts are the debris from collisions of larger bodies, analogous to asteroids and comets, and are often described as “debris disks.” “I would describe Fomalhaut as the archetype of debris disks found elsewhere in our galaxy because it has components similar to those found in our own planetary system,” said András Gáspár of the University of Arizona in Tucson and lead author of a new paper detailing these results. are described. “By looking at the patterns in these rings, we can actually do a little sketch of what a planetary system should look like — if we could actually get a picture deep enough to see the suspected 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 structure inside. The inner belts were first resolved by Webb in infrared light. “What Webb really excels at is that we can physically resolve the thermal glow of dust in those inner regions. So you can see inner belts that we could never see before,” said Schuyler Wolff, another member of the University team. from Arizona.

Hubble, ALMA and Webb are working together to get a comprehensive picture of the debris around a number of stars. “With Hubble and ALMA, we were able to image a number of Kuiper belt analogs and we learned a lot about how outer disks form and develop,” said Wolff. “But Webb should allow us to image a dozen asteroid belts elsewhere. We can learn as much about the inner warm regions of these disks as Hubble and ALMA have taught us about the colder outer regions.”

These belts are probably formed by the gravitational pull of unseen planets. Similarly, in our solar system, Jupiter holds the asteroid belt in check, the inner edge of the Kuiper belt is formed by Neptune, and the outer edge may be led by previously unseen celestial bodies. As Webb images more systems, we will learn more about the configurations of their planets.

The Fomalhaut dust ring was discovered in 1983 during observations from NASA’s Infrared Astronomical Satellite (IRAS). The existence of the ring has also been inferred from previous observations at longer wavelengths with 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: Where are the planets?” said George Rieke, another team member and US scientific chief for Webb’s Mid-Infrared Instrument (MIRI), which made these observations. “I think it’s not a big leap to say there’s probably a really interesting planetary system around the star.”

“We definitely didn’t expect the more complex structure with the second intermediate belt and then the wider asteroid belt,” Wolff added. “That structure is very exciting, because every time an astronomer sees a hole and rings in a disk, they say, ‘There could be a planet inside that is shaping the rings!'”

Webb has also imaged what Gáspár calls “the great dust cloud,” which may be evidence of an outer ring collision between two protoplanetary bodies. This is different from a suspected planet Hubble first spotted in the outer ring in 2008. Subsequent Hubble observations showed that the object had disappeared in 2014. A plausible interpretation is that this new feature, like the previous one, is an expanding cloud of very fine dust particles from two icy bodies that collided.

The idea of ​​a protoplanetary disk around a star dates back to the late 1700s, when astronomers Immanuel Kant and Pierre-Simon Laplace independently developed the theory that the sun and planets formed from a rotating cloud of gas that collapsed due to gravity and flatten. Debris disks form later, after the formation of planets and the dispersion of the primordial gas in the galaxies. They show that small bodies such as asteroids collide catastrophically, crushing their surfaces into huge clouds of dust and other debris. Observations of their dust provide unique clues to the structure of an exoplanetary system, down to Earth-sized planets and even asteroids, which are far too small to see in isolation.

The team’s results are published in the journal Nature Astronomy.

The James Webb Space Telescope is the world’s premier space science observatory. The Fomalhaut observations used the Mid-Infrared Instrument (MIRI), contributed by NASA and ESA (European Space Agency). The instrument was designed and built by a consortium of nationally funded European institutes (the MIRI European Consortium) and NASA’s Jet Propulsion Laboratory, in collaboration with the University of Arizona. Webb will solve mysteries in our solar system, look further into distant worlds around other stars, and investigate the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA and the Canadian Space Agency.

Bron: NASA