NASA's Hubble watches comet ATLAS breakup into over two dozen pieces

The images of comet C/2019 Y4 (ATLAS) taken on April 20 and 23, 2020 by NASA's Hubble Space Telescope yielded new evidence about the breakup of the fragile comet.

Hubble identified about 30 fragments of the comet on April 20, and 25 pieces on April 23. All these fragments of comet ATLAS are enveloped in a sunlight-swept tail of cometary dust. "Their appearance changes substantially between the two days, so much so that it's quite difficult to connect the dots. I don't know whether this is because the individual pieces are flashing on and off as they reflect sunlight, acting like twinkling lights on a Christmas tree, or because different fragments appear on different days,"  said David Jewitt, professor of planetary science and astronomy at UCLA, Los Angeles. Jewitt is also the leader of one of two teams that photographed ATLAS comet with Hubble. 

New @NASAHubble images show comet ATLAS disintegrating, yielding new evidence that breakups are fairly common: https://t.co/MfdIAf5upv pic.twitter.com/cRsmzd2ylI — NASA (@NASA) April 29, 2020

"This is really exciting — both because such events are super cool to watch and because they do not happen very often. Most comets that fragment are too dim to see. Events at such scale only happen once or twice a decade," said the leader of a second Hubble observing team, Quanzhi Ye, of the University of Maryland, College Park.

The researchers remarked that the images captured by Hubble make it clear that comet fragmentation is a common thing. The crisp images captured by Hubble may yield new clues to the breakup as NASA's telescope distinguishes pieces as small as the size of a house. 

The researchers believe that the original nucleus spun itself into pieces because of the jet action of outgassing from sublimating ices and since such venting is probably not evenly dispersed across the comet, it enhances the breakup. "Further analysis of the Hubble data might be able to show whether or not this mechanism is responsible," said Jewitt. "Regardless, it's quite special to get a look with Hubble at this dying comet."

Comet C/2019 Y4 (ATLAS) was discovered on December 29, 2019, by the ATLAS (Asteroid Terrestrial-impact Last Alert System) robotic astronomical survey system based in Hawaii.