According to a press release from the Lyon Observatory dated September 4, 2025, based on a scientific publication to which Elliot Lynch, researcher at CRAL (ENS de Lyon/CNRS/UCBL), contributed as part of an international team: "ALMA Reveals an Eccentricity Gradient in the Fomalhaut Debris Disk", published in The Astrophysical Journal on September 4, 2025.
While the unusual shape of the dust disk surrounding the star Fomalhaut has intrigued astronomers for many years, an international team including Elliott Lynch, researcher at the Lyon Astrophysics Research Center (ENS de Lyon/CNRS/Claude Bernard University Lyon 1), reports significant progress on the subject in a paper published on September 4, 2025, in The Astrophysical Journal . Using observations made with the ALMA telescope - an international astronomical facility - this research team, led by astronomers from the Harvard & Smithsonian Center for Astrophysics and Johns Hopkins University, shows that the asymmetry of this debris ring could be caused by the influence of a planet that has not yet been discovered.
Fomalhaut, one of the brightest stars in the night sky
Using the ALMA radio telescope¹ located in the Atacama Desert in Chile, astrophysicists have obtained the most detailed image yet of the dust disk surrounding Fomalhaut, one of our nearby stellar neighbors. This star, among the brightest in the night sky and one of the most studied, possesses a debris disk with an unusual morphology. Such disks are vast belts of dust and small rocky bodies, similar to the asteroid belt in our Solar System but on a much larger scale. The asymmetry of Fomalhaut’s disk has intrigued researchers for nearly twenty years.
A shape that varies with distance from the star
An international team, including the Lyon Astrophysics Research Center (ENS de Lyon, CNRS, UCBL), has published new results in the Astrophysical Journal. These findings demonstrate that Fomalhaut’s disk is not simply asymmetric, but that its eccentricity varies depending on the distance from the star. Unlike previous models, which assumed a uniform eccentricity, the new observations show that the disk becomes less eccentric as one moves farther from Fomalhaut.
1: Atacama Large Millimeter/submillimeter Array
In red: the dust disk around the star Fomalhaut (center) as seen by the ALMA radio telescope. Dashed: the possible orbit of a planet shaping its asymmetric morphology. © J. B. Lovell and J. Chittidi
Scientific contact: Elliott Lynch. Mail: elliot.lynch [at] ens-lyon.fr ( elliot[dot]lynch[at]ens-lyon[dot]fr )
Reference
LOVELL, Joshua Bennett ; LYNCH, Elliot ; CHITTIDI, Jay ; SEFILIAN, Antranik A. ; ANDREWS, Sean M. ; KENNEDY, Grant M. ; McGREGOR, Meredith ; WILNER, David ; WYATT, Mark C. ALMA reveals an Eccentricity Gradient in the Fomalhaut Debris Disk, The Astrophysical Journal , 2025, vol. 990, 2, p. 145.
[Article link: http s ://iops c’i e. i op.o r g/ a r e /10.3847/1538-4357/ a ]
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