A disk of debris in a nearby star revealed like never before

A disk of debris in a nearby star revealed like never before

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These two images correspond to the dusty debris disk around AU Mic, a red dwarf star located 32 light-years away in the southern constellation of Microscopium. – NASA, ESA, CSA, AND K. LAWSON


The James Webb Space Telescope has obtained images of the inner workings of a dusty disk surrounding a nearby red dwarf star.

These observations represent the first time that an image of the hitherto known disk has been obtained at these infrared wavelengths. They also provide clues about the composition of the record.

The star system in question, AU Microscopii or AU Mic, lies 32 light-years away, in the southern constellation of Microscopium. It is approximately 23 million years old, which means that the formation of planets has finished, since that process usually lasts less than 10 million years. The star has two known planets, discovered by other telescopes.

The dusty debris disk that remains is the result of collisions between leftover planetesimals, a more massive equivalent of our solar system’s dust. which creates a phenomenon known as zodiacal light.

“A debris disk is continually replenished by planetesimal collisions. By studying it, we get a unique window into the recent dynamical history of this system,” he says. it’s a statement Kellen Lawson of NASA’s Goddard Space Flight Center, lead author of the study and a member of the research team that studied AU Mic.

“This system is one of the few examples of a young star, with known exoplanets and a debris disk that is close enough to and is bright enough to study holistically using Webb’s exceptionally powerful instrumentssaid Josh Schlieder of NASA’s Goddard Space Flight Center, principal investigator for the observing program and co-author of the study.

The team used Webb’s Near Infrared Camera (NIRCam) to study AU Mic. With the help of NIRCam’s coronagraph, which blocks the intense light from the central star, they were able to study the region very close to the star. The NIRCam images allowed the researchers to track the disk as close to the star as 5 astronomical units, the equivalent of Jupiter’s orbit in our solar system.

“Our first look at the data far exceeded our expectations. It was more detailed than we expected. It was brighter than we expected. We detected the disk closer than we expected. We hope that as we go deeper, there will be more surprises that we had not anticipated.“Schlieder stated.

The observing program obtained images at wavelengths of 3.56 and 4.44 microns. The team found that the disk was brighter at the shorter wavelength, or “bluer,” which probably means that it contains a large amount of fine dust that is more efficient at scattering shorter wavelengths than light. light. This finding agrees with the results of previous studies, according to which the radiation pressure of AU Mic -unlike that of more massive stars- it would not be strong enough to eject fine dust from the disc.

Although detecting the disk is important, the team’s ultimate goal is to search for giant planets in wide, Jupiter-like orbits, Saturn or the ice giants of our solar system. These types of worlds are very difficult to detect around distant stars using the transit or radial velocity methods.

“This is the first time that we have sensitivity to directly observe planets with wide orbits and significantly lower masses than Jupiter and Saturn. This is really new and unexplored territory in terms of direct imaging around low-mass stars,” he explained. Lawson.

These results were presented at the 241st meeting of the American Astronomical Society (AAS).

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