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Saturday, April 11, 2020

The Coming of Comet C/2019 Y4 ATLAS

One of the great things about staying at home - you just, might discover a comet! Ninety-four (94) new comets were discovered by Amateur Astronomers, last year.

The last, great comet that I saw was comet Hale-Bopp, in 1997. When I say, "Great" - I mean that it was so prominent in the sky that, if you were facing about 70-80 degrees away from it, it still caught your attention out of the corner of your eye. Now, THAT's, "Great"!

Another comet that I've always considered to be, "Great" - was comet Hyakutake (C/1996 B2). Most people don't remember that one - but, that's only because, it was so large, that it was difficult to see as a singular, intact object. The tail of the comet was so wide, and was positioned, directly overhead, that it looked more like a disintegrating, diffuse, airliner contrail - spanning nearly the entire sky, and with no, distinct "head".

Comet C/2019 Y4 ATLAS imaged on the 16" f/3.7 astrograph reflector, ATEO-1 on the evening of April 10, 2020, by Muir Evenden. Processing by Utkarsh Mishra and Michael Petrasko.
Comet C/2019 Y4 ATLAS imaged on the 16" f/3.7 astrograph reflector, ATEO-1 on the evening of April 10, 2020, by Muir Evenden. Processing by Utkarsh Mishra and Michael Petrasko.

But, enough about those "Great visitors" to the Inner Solar System - there just might be, another, looming presence in the night. Enter, comet C/2019 Y4 ATLAS, or, comet "ATLAS", for short!) ATLAS is a sort of, "Rip Van Winkle"; it's been "asleep", since about the year 3000 BC! The chart, here, shows the comet's expected positions in the sky, from, 20MAR, in Ursa Major - 28JUN, 2020 in Orion. Currently, it is "cat-napping", in the northern constellation, Camelopardalis. On 12MAY, the comet moves into the constellation Perseus, and on the 23rd, it will be at its closest to Earth. It will be at its closest to the sun on 31MAY 2000.

The dirty "snow-ball" - as we like to call these things - was discovered by one of the Asteroid Terrestrial-Impact Last Alert System's (ATLAS) 0.5 m (20 in) reflector telescopes, situated at the top of Mauna Loa, Hawaii. At the time of discovery, in December of 2019, it was 3 AU's from the sun, at magnitude 19.6. By the beginning of February, it brightened to magnitude 17, and then, to mag. 8, by the end of March of this year.

The predicted path of Comet C/2019 Y4 ATLAS thru June 18th, 2020. Graphic credit: www.cometwatch.co.uk
The predicted path of Comet C/2019 Y4 ATLAS thru June 18th, 2020. Graphic credit: www.cometwatch.co.uk

ATLAS has a very distinctive coloration; green/aqua, due to, diatomic carbon molecules, within its coma. Its orbital period was originally thought to be around 4,400 years. ATLAS, has some orbital characteristic similarities with the Great Comet of 1844 (C/1844 Y1), suggesting that this "new" (to us) comet might, actually, be a remnant fragment of the same parent body as C/1844 Y1. This apparition of ATLAS, was, initially, held to be, possibly a spectacular one - and, that may still be the case. However - recent observations have shown a decrease in magnitude, after having brightened to magnitude 8, as it crossed the orbit of Mars. It is currently at magnitude 8.9 - 9.2. This is not even naked, or, unaided-eye visibility. That's because the comet is fragmenting. It is still possible, that, the fragments will maintain enough structural integrity, to give the broken comet, higher scores - possibly, something along the lines of comet Shoemaker-Levy's plunge into the atmosphere of Jupiter, years ago! (We couldn't see that from the ground, but it was spectacular on a spacecraft video feed!).

Well, who knows?! When ATLAS is done, doing what it's going to do - it will head back out into the cosmic depths, on a 5,200 year-long loop, eventually, to bring it back around to the sun, once again. Along the way, it may even leave behind, a generous portion, of its disintegrating self in the form of a new meteor shower stream!

Dale Alan Bryant
Senior Contributing Science Writer

1 comment:

  1. Whenever a comet image is noted to have become oblong, as has recently been shown, it always means that the comment is beginning to fragment. But if this is the case, given the comet's proximity to the Sun, those fragments may remain intact long enough to give a Whopper of a display! on the other hand, comments are notoriously unpredictable, as has been shown throughout history. Personally, I will hope for the best.

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