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An international team of astronomers have employed the James Webb Space Telescope (JWST) to observe a nearby M-dwarf star known as TWA 20. As a result, they detected a large debris disk around this star. The finding was reported in a October 23 on the arXiv pre-print server.

Debris disks are collections of small bodies around stars, including asteroids, Kuiper belt objects, comets, and also micron-sized debris dust. Detection of new debris disks and their investigation could help us better understand the evolution of planetary systems, the composition of dust, comets, and planetesimals outside our solar system.

TWA 20 is a faint M dwarf of spectral type M3, located some 261.5 light years away from Earth. It is a young star with an estimated age of about 10 million years and its effective temperature is 3,560 K.

In June 2024, a group of astronomers led by Skyler Palatnick of the University of California, Santa Barbara, utilized JWST's near-infrared camera (NIRCam) to perform coronagraphic observations of TWA 20. The observational campaign yielded important insights into the star's surroundings.

"In this work, we report on the imaging discovery of a debris disk in scattered light around the TWA 20 host star. The images were obtained with JWST/NIRCam as part of the GO 4050 survey and processed using RDI [reference differential imaging] and MCRDI [model-constrained RDI]," the researchers explained.

The observations found that TWA 20 is surrounded by a debris disk with a radius of 64.7 AU and an inclination of 70.1 degrees. The position angle of the disk was measured to be -132.9 degrees and its peak brightness was established to be 0.1 MJy/sr.

The astronomers noted that the disk of TWA 20 is one of the six resolved M-dwarf debris disks that have been imaged in scattered light, and among these is one of two that show no measured infrared excess. Moreover, it is the third largest of the M-dwarf disks and orbits the third faintest host star.

Palatnick's team compared the properties of the newfound disk to other ones around M dwarfs. It turned out that it has a comparable radius and brightness to these disks.

By analyzing the JWST observations, the astronomers found no evidence of a companion object in the system. The collected data likely rule out a Jupiter mass perturber at separations wider than 48 AU.

Summing up the results, the authors of the paper underscored the capabilities of JWST when it comes to the identification of debris disks.

"The detection of this disk exemplifies the sensitivity of JWST to debris disks around low-luminosity host stars, which have historically been difficult to detect because these disks are cool and dim," the scientists conclude.

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