2023-05-12 14:43:51
The James Webb Space Telescope reveals the planetary system of the star Fomalhaut in never-before-seen detail, including interlocking concentric dust rings. They are most likely sculpted by the gravitational forces produced by present but invisible planets.
In the vicinity of the Milky Way, 25 light-years from us, is the star Fomalhaut, in the constellation Pisces austral: this planetary system is seen by the James-Webb space telescope (JWST) in breathtaking detail, in mid-infrared.
Its concentric rings of dust are intertwined and sculpted by planets which are buried there but which remain invisible to the eye of the instrument. The mechanism that holds these circles in position is similar to that within our Solar System that causes Jupiter to hold the asteroid belt located between it, Mars and our planet Earth.
As for the Kuiper Belt, still in the Solar System, its inner edge is carved by the glacial giant Neptune; its outer edge might be framed by as yet unknown bodies located beyond this belt.
>> Solar System asteroids:
On the left, the inner Solar System with the asteroid belt located between Mars and Jupiter, as well as the Trojan asteroids, in the same orbit as Jupiter. On the right, the orbit of the outer planets and the most distant Kuiper belt objects. [Caltech – NASA]
Fomalhaut is sixteen times brighter than the Sun and almost twice as massive. It is regarding 440 million years old, less than a tenth the age of the Sun, but has probably reached half of its lifespan.
The three interlocking belts extend up to 23 billion kilometers from Fomalhaut, or regarding 150 times the Earth-Sun distance.
A planetary system model
Astronomers discovered Fomalhaut’s first disc in 1983, but there’s never been a sight more spectacular – or more eye-opening – than the one taken by the JWST. With this studypublished May 8 in the journal Nature Astronomy, highlights two new belts of rocky and icy debris orbiting the star, a complex framework.
“I would describe Fomalhaut as the archetypal debris disks found elsewhere in our galaxy, as its components are similar to those of our own planetary system,” according to the study’s lead author, András Gáspár, astronomer assistant at the Steward Observatory of the University of Arizona, quoted in a communiqué of the institution.
The Fomalhaut star system: the inner disk, the inner void, the intermediate belt, the outer void, the outer belt and the halo. On the right, a large dust cloud is highlighted, visible in two infrared wavelengths, 23 and 25.5 microns. [András Gáspár (University of Arizona), Alyssa Pagan (STScI) – NASA, ESA, CSA]“By observing the patterns of these rings, we can begin to make a small sketch of what a planetary system should look like – if we might actually take a picture deep enough to see the planets we suspect exist.” According to the astronomer, the secondary gap observed in the system is a strong indication of the presence of an ice giant.
Asteroids pulverized
These three belts seem to be populated by objects called planetesimals, some of which are believed to come together early in the history of a star system to form planets, while others remain in the state of debris, such as the asteroids and comets.
It is following the formation of the planets, once the primordial gas has dispersed, that the discs of debris are formed. When small bodies like asteroids collide, their surfaces are pulverized into huge clouds of dust and other debris.
Observing them provides unique clues to the structure of an exoplanetary system, down to Earth-sized planets and even asteroids, which are far too small to observe individually.
“Like our Solar System, other planetary systems are home to discs of asteroids and comets – remnants of planetesimals from the time of planet formation – which are continually shrinking into particles the size of a micron through collisional interactions,” explains András Gáspár.
>> Read also: A NASA probe will fly over a relic of the beginnings of the Solar System
Better understand the birth of the planets
The study of these belts of debris allows us to better understand the birth of planets: “They form in the primordial disks that surround young stars. To understand this process of formation, we must fully understand how these disks form and evolve” , notes Schuyler Wolff, co-author of the study, working in the same place as his colleague.
“Many questions remain unanswered: how the dusts of these discs come together to form planetary embryos, how planetary atmospheres are formed, etc. The debris discs are remnants of this process of planet formation and their structure can provide valuable clues to underlying planetary population and dynamic histories.”
Stephanie Jaquet and Archyde.com
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