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| These images depict the dusty debris disk around AU Mic, a red dwarf star 32 light-years away in the constellation Microscopium. Utilizing Webb’s NIRCam equipped with a coronagraph, scientists studied the region near the star, with the star’s location marked in white and the blocked region shown by a dashed circle. |
In 2023,NASA’s James Webb Space Telescope has provided unprecedented insights into the inner workings of a dusty disk enveloping a nearby red dwarf star. Representing a breakthrough in astronomical observation, these findings offer valuable clues to the composition and dynamics of such stellar systems.
The star at the center of this discovery, AU Microscopii (AU Mic), resides a mere 32 light-years away in the constellation Microscopium. Despite its relative proximity, AU Mic presents a unique celestial laboratory due to its youthful age of approximately 23 million years. This age places it past the prime period of planet formation, a process typically completed within 10 million years. AU Mic boasts two confirmed planets, previously identified by other telescopes.
The dusty debris disk surrounding AU Mic is the residue of collisions between planetesimals—larger counterparts to the dust particles prevalent in our solar system, responsible for the phenomenon known as zodiacal light. Continuously replenished by ongoing collisions, this debris disk offers astronomers a rare glimpse into the recent evolutionary history of the AU Mic system.
Lead author Kellen Lawson of NASA’s Goddard Space Flight Center notes, “A debris disk is continuously replenished by collisions of planetesimals. By studying it, we get a unique window into the recent dynamical history of this system.”
Principal investigator Josh Schlieder adds, “This system is one of the very few examples of a young star, with known exoplanets, and a debris disk that is near enough and bright enough to study holistically using Webb’s uniquely powerful instruments.”
Utilizing Webb’s Near-Infrared Camera (NIRCam) equipped with a coronagraph, the research team was able to peer deeply into the inner regions of the AU Mic system, capturing images of the disk as close as 5 astronomical units from the star—equivalent to Jupiter’s orbit in our solar system.
The observations, conducted at wavelengths of 3.56 and 4.44 microns, revealed intriguing characteristics of the dusty disk. Notably, the disk appeared brighter at shorter, “bluer” wavelengths, indicating the prevalence of fine dust particles adept at scattering shorter wavelengths of light. This finding aligns with previous studies suggesting that AU Mic’s radiation pressure is insufficient to expel such fine dust from the disk.
While the detection of the debris disk marks a significant milestone, the team’s primary objective is to search for gas giant planets in wide orbits akin to Jupiter or Saturn. Such planets pose a considerable challenge to detect around distant stars using conventional methods like transit or radial velocity observations.
Lead author Lawson remarks, “This is the first time that we really have sensitivity to directly observe planets with wide orbits that are significantly lower in mass than Jupiter and Saturn. This really is new, uncharted territory in terms of direct imaging around low-mass stars.”
These groundbreaking findings, unveiled at the 241st meeting of the American Astronomical Society, represent a testament to Webb’s capabilities in unlocking the mysteries of our universe. The observations were conducted under Webb’s Guaranteed Time program 1184, promising further revelations as astronomers continue to explore the cosmos with unprecedented precision and clarity.