JWST discovers debris disk

Newly imaged debris disk around M dwarf star Fomalhaut C. The right panel shows the outline of the debris disk detected in thermal emission. Adapted from Lawson et al. 2024 JWST has achieved another first: for the first time, the telescope has spotted light scattered by dust particles in the debris disk around the star Fomalhaut C. These observations expand our knowledge of planet formation processes around the smallest and most abundant star in the galaxy. Fleeting Phases While stars and planets form from collapsed clouds of gas and dust, emerging planetary systems go through a short-lived and poorly understood phase. The volatile debris disk phase lasts only 10 million years and is characterized by collisions between protoplanets that form a disk or ring of dust and debris. The study of debris disks is key to understanding the formation of planetary systems. Few debris disks have been observed around M dwarfs – the smallest, coolest and most common type of star in the Milky Way – and detailed observations of the few known M dwarf debris disks are scarce. Studies are divided on whether low-mass stars are less likely to host debris disks or whether these disks are simply harder to detect. Fortunately, JWST is able to detect these elusive disks, and recent observations have given researchers a new perspective on the disks surrounding M dwarf stars just 25 light-years away. Fomalhaut is a triple star system best known for its debris disk and the hotly debated planet candidate surrounding Fomalhaut A, the largest and most luminous star in the system. During observations with the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers had previously detected thermal emission from a debris disk surrounding the M dwarf star in the system, Fomalhaut C, but subsequent observations failed to detect the disk in scattered light. Scattered light observations provide researchers with valuable information about the size and composition of dust particles in the disk. Recently, a team led by Kelen Lawson (NASA Goddard Space Flight Center) pointed JWST at Fomalhaut C and eight other nearby M dwarf stars to search for planets around these stars. In JWST’s 3.56 and 4.44 micron filters (1 micron = 10-6 meters), the authors found a faint disk extending beyond the star. In the shorter wavelength filters, the outline of the disk matched the location of the debris disk previously observed with ALMA. In the longer wavelength filters, the disk extended slightly beyond the emission observed with ALMA. Challenging Observations Fomalhaut C is the smallest and coolest star whose disk has been discovered in scattered light. The new observations highlight JWST’s ability to detect debris disks around small, cool stars, as well as the inherent difficulty of observing these structures. Even under JWST’s watchful gaze, the star’s debris disk is only faintly visible, with background objects and noise obscuring the view. of the telescope. Difficult observation conditions made it difficult to analyze the disk’s properties. Difficulty in subtracting background light could be the cause of the disk’s unexplained red color. But the team was still able to look for planets. Lawson’s team ruled out the presence of a planet with a mass greater than Saturn orbiting at a distance of 10 astronomical units, and a planet with a mass greater than Jupiter orbiting its star at a distance of 5 astronomical units. Subsequent observations of Fomalhaut C may further improve our understanding of its debris disk, and future observations by JWST will certainly expand the small but important sample of debris disks surrounding the smallest stars.

source: https://doi.org/10.3847/2041-8213/ad4496