Comet ATLAS (C/2019 Y4)

Comet ATLAS on March 28th. Credit: Tim Connolly of Plattsburgh, NY.
Comet ATLAS (C/2019 Y4), what are you doing? New data from astronomers around the world show that the once-promising comet is beginning to fade. For Karl Battams of the Naval Research Lab in Washington DC, it could be a classic case of "I told you so."

"Quoting myself from March 15th," says Battams, "'I wouldn't be surprised to see Comet ATLAS start to fade rapidly and possibly even disintegrate before reaching the sun.' I very much hope I'm wrong, but Comet Elenin did something similar several years ago, holding lots of promise and then just... fizzling."

Comment: Comet Elenin nucleus was fragmented by a Coronal Mass Ejection. Source

In recent months, Comet ATLAS galvanized astronomers as it fell toward the sun, skyrocketing in brightness like few comets before it. By late May 2020 it promised to rival Venus in the sunset sky. But recent developments belie that possibility.

Comet ATLAS (C/2019 Y4)

Images from the 0.6-m Ningbo Education Xinjiang Telescope show a possible fragmentation of ATLAS’s core
On April 6th, astronomers Quanzhi Ye of the University of Maryland) and Qicheng Zhang of Caltech reported new images of Comet ATLAS, in which the comet's core appears to be elongating-"as would be expected from a major disruption of the nucleus," they wrote in an Astronomical Telegram.

"It's possible that this is the beginning of the end," says Battams.

Recent measurements of the comet's position also point to trouble. Battams explains: "The comet's orbit is now being influenced by 'non-gravitational' forces. These forces are the result of gases lifting off the comet nucleus and causing the nucleus to move very slightly in the opposite direction-sort of like a jet engine. Most active comets experience this to some degree, but ATLAS's non-gravitational forces have kicked in very abruptly and are quite strong. This supports a narrative of a small nucleus being pushed very strongly by extreme outgassing, possibly along with fragmentation."

Comment: ...and strong electrical activity. Comets can 'go backwards', which is related to why meteors can 'change direction' and 'go real slow' in Earth's upper atmosphere.

"Finally, let's not forget that ATLAS is a fragment of a larger (unidentified) comet also related to the Great Comet of 1844," says Battams. "Fragmenting is a family trait for these guys."
Comet ATLAS (C/2019 Y4)
Is Comet ATLAS doomed? Not necessarily. "The frustrating thing about comets is we often don't know exactly what they're doing or why they're doing it. There's still a chance that Comet ATLAS is just 'taking a breather' before another outburst," says Battams. "But I wouldn't count on it...."

No matter what happens, amateur astronomers are encouraged to monitor developments. Submit your images here.

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