The NASA/ESA Hubble House Telescope has provided astronomers with the sharpest view but of the breakup of Comet C/2019 Y4 (ATLAS). The telescope resolved around 30 fragments of the fragile comet on 20 April and 25 pieces on 23 April.
The comet was first observed in December 2019 by the ATLAS (Asteroid Terrestrial-impact Last Alert System) robotic astronomical survey system in Hawaii, USA. It brightened rapidly until mid-March, and a few astronomers initially anticipated that it might be seen to the naked eye in May to turn into one of the most spectacular comets seen within the last two decades. Nonetheless, the comet abruptly started to get dimmer, leading astronomers to speculate that the icy core could also be fragmenting, and even disintegrating. ATLAS’s fragmentation was confirmed by amateur astronomer Jose de Queiroz, who photographed around three pieces of the comet on 11 April.
The Hubble Space Telescope’s new observations of the comet’s breakup on 20 and 23 April revealed that the damaged fragments are all enveloped in a sunlight-swept tail of cometary mud. These pictures present further proof that comet fragmentation might be frequent and might even be the dominant mechanism by which the stable, icy nuclei of comets die.
Because comet fragmentation happens shortly and unpredictably, reliable observations are rare. Subsequently, astronomers remain largely uncertain about the reason for fragmentation.