2023-05-09 13:16:12
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Fomalhaut — understand “the mouth of poissonpoisson » — is the brightest star in a small constellationconstellation visible from Earth, the Southern Fish. A starstar young person located only 25 light yearslight years of our planet. She is known to astronomersastronomers — even amateurs — because she is the one around orbitorbit Fomalhaut b, the first exoplanetexoplanet to have been photographed. It was by the télescope spatial Hubbletélescope spatial Hubblein 2008, before it simply came to… disappear!
Of new data returned by the James-Webb Space Telescope (JWST) seem to want to confirm that this exoplanet was in fact not really one. That the object captured by Hubble was more the remains of a collision between planets forming a cloudcloud of dust. A cloud which, on the new images studied by astronomers, “fading and expanding”.
It is precisely also the disks of debris that the researchers identified around Fomalhaut in the 1980s that led them to take a close interest in this star. Belts of dust formed by collisions, between bodies of the asteroid or comet type, this time. The Hubble Space Telescope and the Herschel Space Observatory, as well as theAtacama Large Millimeter/submillimeter Array (Alma), had already taken sharp images of the outermost belt. “These instruments have taught us a lot regarding how these records form and evolve”explains Schuyler Wolff, a researcher at the University of Arizona (United States), in a NASA communiqué.
But today it is the James-Webb space telescope which offers researchers the chance to observe the structure of the inner belts of Fomalhaut. Thanks to its ability to “Physically solve the thermal glow of the dust in these regions”. And what the JWST has just revealed to astronomers is that the dusty structures around Fomalhaut are much more complex and dynamic than the asteroid and dust belts — the Kuiper beltKuiper belt — found in our Solar systemSolar system.
A planetary system around Fomalhaut?
The researchers note the existence of three interlocking belts extending up to 23 billion kilometers from the star. The equivalent of 150 times the distance from our Earth to the Sun. With an outer belt that looks a lot like our Kuiper belt. Twice as wide, however. But what is really new is the description that astronomers give of the belt closest to the star and of a asteroid beltasteroid belt intermediate. The latter appears inclined at 23° with respect to the rest of what revolves around Fomalhaut.
“There is probably a really interesting planetary system around Fomalhaut”
“I think it’s not too much to say that there’s probably a really interesting planetary system around Fomalhaut. remarks George Rieke, the head of the Mid-Infrared Instrument(MiriMiri) from the James Webb Space Telescope. Because astronomers have long imagined that debris disks grow following planets form when small bodies like asteroids collide and pulverize their surfaces into huge clouds of dust, all sculpted by the gravitational forces produced by planets, as is the case in our solar system where JupiterJupiter circles the asteroid belt and where the inner edge of the Kuiper belt is shaped by Neptune while its outer edge might be carved by the infamous and ever-elusive Planet X.
Thanks to the JWST, the researchers were also able to observe a structure which they named “The Great Cloud of Dust”, potential evidence that a collision occurred in Fomalhaut’s outer ring between two protoplanetary bodies — but it might also be a distant object seen through the debris, new observations should help determine. Another collision than the one mentioned to explain the strange disappearance of Fomalhaut b. And another proof that the Fomalhaut system is potentially complex and active.
Exceptional image of a ring of dust around a star
As part of an extensive search program for clues to the existence of extrasolar planets, the Hubble Space Telescope has achieved a great feat by taking the most detailed picture ever obtained of a particularly narrow ring of dust around the Fomalhaut star. This image suggests that a currently invisible planet might deform it and thus betray its presence. Especially since computer simulationscomputer simulations confirm its existence due to disturbances affecting the star.
Article of Remy DecourtRemy Decourt published on 07/16/2005
Scientists confirm that they might even have seen the planet if it had been five times more massive than Jupiter. Further observations are planned this summer to complete the picture. (the ring is too big to stay in the field of the camera, which explains the missing part) and analyzes of colorscolors of the ring are also provided to determine its properties physiquesphysiques and its composition.
Some readily compare this ring to the Kuiper belt of the Solar System. This belt is made up of the remnants of the formation of the planets. These are blocks of mattermatter which are not agglomeratesagglomerates to other planetoids.
The choice of Fomalhaut (HD 216956) is not trivial. It is one of the nearest stars surrounded by a disk of dust and gazgaz. Above all, its position relative to the Earth allows Hubble to be well positioned to observe it, which is not the case, for example, of better known stars also surrounded by such a disc as beta-Pictoris and from Au Microscopy. They are presented under the edge, which makes their observation very difficult.
But observing Fomalhaut is not easy. The star is very bright and therefore hides the details of its disk structure. Hubble therefore used the coronographecoronographe of the ACS, which makes it possible to hide the light of a star and to see the devices which surround it. The image thus obtained has a sensitivity and a resolutionresolution high. In the case of Fomalhaut, the Hubble images have a resolution of regarding 0.5 UAUAi.e. 75 million km.
Fomalhaut is located near the SoleilSoleilonly 25 light-years away but it is twice as massive as our star and not very old, only 200 million years, one twentieth of the age of the Sun. It is the brightest star in the constellation Pisces.
If we refer to the Solar System, this period corresponds to the great bombardmenta period that lasted more than 700 million years following the formation of the Sun and where 14 million objects impacted the Earth and enriched it with different materials. This period is exciting because it marks the transition between the birth of the planets and their ‘final’ state. The Moon was bombarded by over 1 million objects which gave rise to the craters seen today. On Mars, the cometscomets brought large quantities of water and all the atmospheresatmospheres planets have been strongly modified by this episode. Note that there is no fossilfossil or index of this period on Earth which throughout its history has known many surface upheavals.
The Hubble image clearly shows a narrow ring, only 25 AU wide, starting at a distance of 133 AU from its star and stretching out to 159 AU. By comparison, the Kuiper Belt is 30 AU from the Sun and extends out to 50 AU from the Sun (well beyond the orbit of PlutonPluton). But while the star’s disk is analogous to the Kuiper Belt, its diameter is four times larger.
The edge of the cloud is very sharp, resembling the edge of a knife blade. It is basically sliced. It resembles the rings of Saturn, where we observe very fine structures maintained by small shepherd satellites. The ring does not appear centered on the star but on a spot of 2.25 billion km which seems to take the leading role. The laws of movementmovement of Kepler declare that objects describing elliptical orbits are always offset from the geometric center of the ellipse. In the present case, this offset implies a planet traversing a highly elliptical orbit which also sweeps up and absorbs the dust making up the disc, much like Neptune and the larger planets of our Solar System sucked up the debris forming the primitive dust disc that surrounded our Sun, leaving a distant ring of debris rocky (the Kuiper belt).
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