James Webb shows rings of debris around star – 5/9/2023 – Science

There has been a lot of excitement over the past few decades about planets being detected orbiting various stars outside our solar system. But planets offer an incomplete picture of the complex structure that exists around stars, leaving out components like the belts of rocky and icy debris orbiting our Sun.

Scientists on Monday unveiled observations from the James Webb Space Telescope that show new details about such features around a luminous star called Fomalhaut in our own galaxy, the Milky Way. These observations of three dusty concentric rings of debris around Fomalhaut provide the most complete view to date of these structures outside our solar system.

Fomalhaut, one of the brightest stars in our night sky and the brightest in the southern constellation of Piscis Austrinus, is located 25 light years from Earth. A light year is the distance that light travels in one year, 9.5 trillion kilometers.

Astronomers first discovered a debris belt around Fomalhaut in 1983. Webb telescope observations revealed two other rings closer to the star — a bright inner one and a narrow, intermediate one.

These three belts appear to be populated by objects called planetesimals, some of which are believed to come together early in a star system’s history to form planets, while others remain as debris in the form of asteroids and comets.

“Much like our solar system, other planetary systems host disks of asteroids and comets — remnants of planetesimals from the epoch of planet formation — that continually reduce to micron-sized particles through collisional interactions,” said the astronomer Andras Gaspar, from the University of Arizona, lead author of the study published in the journal Nature Astronomy.

Fomalhaut is 16 times more luminous than the Sun and almost twice as massive. It’s about 440 million years old — less than a tenth the age of the Sun — but it’s probably about halfway through its lifespan.

The three nested belts extend as far as 23 billion km from Fomalhaut, about 150 times the distance from Earth to the Sun.

Although no planets have yet been discovered around Fomalhaut, researchers suspect that the belts were carved out by gravitational forces exerted by unseen planets. Our Solar system has two such belts — the main asteroid belt between the rocky planet Mars and the gas giant Jupiter, and the Kuiper belt, beyond the icy giant Neptune.

The gravitational influence of Jupiter, the largest planet in our Solar System, corners the main asteroid belt. The inner edge of the Kuiper belt, which is home to the dwarf planets Pluto and Eris, as well as other icy bodies of varying sizes, is shaped by the outermost planet, Neptune.

“The secondary gap we see in the system is a strong indication of the presence of an ice giant in the system,” said Gaspar.

The observations from Webb, which launched in 2021 and began collecting data last year, were made by its Mid-Infrared Instrument (MIRI).

“Almost all of the resolved debris disk images so far have been of the cold, outer regions analogous to the Solar System’s Kuiper belt,” such as the outer Fomalhaut belt, said astronomer and study co-author Schuyler Wolff of the University’s Steward Observatory. from Arizona.

MIRI will now be able to resolve relatively hotter belts of material analogous to our main asteroid belt, Wolff said.

Studying these debris belts offers insight into planetary beginnings.

“Planets form within the primordial disks that surround young stars. Understanding this formation process requires a thorough understanding of how these disks form and evolve,” said Wolff.

“There are many open questions about how dust from these disks coalesces to form planetary embryos, how planetary atmospheres form, etc. Debris disks are remnants of this planet-forming process, and their structure could provide valuable clues to the population.” of underlying planets and dynamic histories,” added Wolff.

^{Translated by Luiz Roberto M. Gonçalves}