New high-resolution images of the Fomalhaut A system from the NASA/ESA/CSA James Webb Space Telescope show three debris belts extending out to 23 billion km (14 billion miles) from the star. The scale of the outermost belt is roughly twice the scale of our Solar System’s Kuiper belt. The inner belts — which had never been seen before — were revealed by Webb for the first time.
This image, taken with Webb’s Mid-Infrared Instrument (MIRI), shows the dusty debris disk surrounding Fomalhaut A. Image credit: NASA / ESA / CSA / A. Gáspár, University of Arizona / A. Pagan, STScI.
The Fomalhaut star system contains three stars: Fomalhaut A, Fomalhaut B and Fomalhaut C.
The name Fomalhaut derives from the Arabic name for this star — Fum al Hut, meaning ‘the Fish’s Mouth.’
Fomalhaut A, the 18th brightest star visible in night sky, is located about 25 light-years away in the constellation of Piscis Austrinus.
This A-type star has been featured in science fiction novels by writers Isaac Asimov, Stanislaw Lem, Philip K. Dick, and Frank Herbert.
Also known as alpha Piscis Austrini and HD 216956, Fomalhaut A is 440 million years old, or about one-tenth the age of the Solar System.
The star is twice as massive as the Sun and 20 times brighter, and is surrounded by a ring of dust and debris.
“I would describe Fomalhaut A as the archetype of debris disks found elsewhere in our Galaxy, because it has components similar to those we have in our own planetary system,” said Dr. András Gáspár, an astronomer at the University of Arizona.
“By looking at the patterns in these rings, we can actually start to make a little sketch of what a planetary system ought to look like — if we could actually take a deep enough picture to see the suspected planets.”
Dr. Gáspár and colleagues analyzed images taken of the debris system around Fomalhaut A using Webb’s Mid-Infrared Instrument (MIRI).
The images show a previously known outer ring considered analogous to the Kuiper belt, as well as a previously unseen narrow intermediate belt that may be shepherded by the gravitational influence of unseen planets — suggesting the presence of a planet in the gap between the belts.
The newly-discovered intermediate belt is misaligned relative to the outer belt, and the astronomers suggest it may have been the origin of a previously known dust cloud generated by a collision.
The images also reveal a large dust cloud within the outer ring, which the researchers name the ‘great dust cloud’, potentially created by another collision.
The structures of the debris belts, their alignment, and evidence of collision events suggest that Fomalhaut A is surrounded by a dynamically active planetary system.
“The belts around Fomalhaut A are kind of a mystery novel: Where are the planets?” said Dr. George Rieke, an astronomer at the University of Arizona and U.S. science lead for Webb’s MIRI instrument.
“I think it’s not a very 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 broader asteroid belt,” said Dr. Schuyler Wolff, also from the University of Arizona.
“That structure is very exciting because any time an astronomer sees a gap and rings in a disk, they say, ‘There could be an embedded planet shaping the rings’.”
The findings appear in the journal Nature Astronomy.
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A. Gáspár et al. Spatially resolved imaging of the inner Fomalhaut disk using JWST/MIRI. Nat Astron, published online May 8, 2023; doi: 10.1038/s41550-023-01962-6
