Astronomers Discover Ultra-Faint Milky Way Satellite in Gemini Constellation
Researchers have discovered a compact, ultra-faint satellite system in the Gemini constellation using data from the DECam survey and confirmed it with spectroscopic observations from Keck and Gemini telescopes. The system, named DELVE 8/Gemini I, is located approximately 120,000 light-years away and has properties that make it difficult to classify as either a dwarf galaxy or star cluster. The discovery demonstrates the capability of current surveys to detect increasingly faint systems and suggests similar objects will be found more frequently with upcoming astronomical surveys.
Astronomers have identified a previously unknown compact satellite orbiting the Milky Way in the constellation Gemini through cross-matching detections from independent search algorithms applied to DECam survey data. The system, designated DELVE 8/Gemini I, is exceptionally faint (absolute magnitude of -2.1) and compact, with a half-light radius of approximately 8.6 parsecs, located at a heliocentric distance of 120 kiloparsecs. Confirmation came through deeper imaging from Gemini/GMOS-N and medium-resolution spectroscopy from Keck/DEIMOS, which identified four member stars including two blue horizontal branch stars and established a mean radial velocity of -82.7 km/s. The system's physical properties place it in an ambiguous category that cannot be definitively classified as either a dwarf galaxy or star cluster based on morphology alone, though spectroscopic evidence suggests an ancient age with metallicity below -2.5 in iron content. This discovery exemplifies the sensitivity of modern astronomical surveys and indicates that similar ultra-faint, distant systems will become increasingly common as survey capabilities improve.
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- arXiv astro-phCenter
Discovery and Spectroscopic Characterization of a Distant, Compact Milky Way Satellite in Gemini
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