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/3.75 Dream Aerospace Systems 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 31 May 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

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, bringing 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

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Observing the Summer Milky Way with Binoculars

Late summer is one of the best times of year to observe the full brilliance of our home galaxy, the Milky Way.

The Milky Way used to be visible on every clear, moonless night, everywhere in the world. Today, however, most people live in places where it's impossible to see the Milky Way because of overall light contamination caused by lights left on all night long. Seeing the Milky Way requires a special effort for most people, but it's well worth the effort. 

Milky Way with North America Nebula and Comet Hale-Bopp Image by Michael Petrasko, 

Muir Evenden and Tom Lucia

To see the Milky Way, you'll need to travel far from any city, to a rural area. Even in a rural farming country, there are still a lot of bright lighting fixtures that wipe out the night sky. I am fortunate to live in a dark area on Cape Cod where there are no street lights of any kind to hinder my view of our galaxy.

The clearest skies appear just after a cold front passes through. This time of the year in September, this happens more often. Even then, you need to spend some time under a dark sky before your eyes become fully adapted to the darkness. It takes about 15 to 20 minutes for human eyes to become fully sensitive to faint light.

What does the Milky Way look like? Not like any of the photographs you see online because those are made with cameras that accumulate light in ways the human eye cannot. What you will see is a faint, whitish glow, stretching in a huge arc from the southern to the northeastern horizon. It has a mottled effect, kind of like a fluffy cloud. There are brighter areas, especially down toward the core of the galaxy in the southern part of the sky. There are also darker patches, where nearby clouds of interstellar dust block the light from beyond.

Orion 9x63 Mini Giant Astronomy Binoculars

The most obvious of these dark nebulae is the Northern "Coal Sack", just below and to the right of the bright star Deneb in the constellation Cygnus. Just below Deneb is one of the brightest parts of the northern Milky Way, worth examining with binoculars. This is the North America Nebula, famous in pictures for its resemblance to the continent of North America. Under a very dark sky seeing with my 9x63 Orion astronomy binoculars, I am just able to see the "continent" feature.

One thing you won't see in the Milky Way, either in binoculars or with the naked eye, is any color. Images register the reddish glow of hydrogen gas, but the light is too faint to trigger the color receptors in the human eye, so all you'll see are shades of grey.

In the northern range of the Milky Way's arc, you'll see the constellations Cassiopeia and Perseus. When you look in that direction, you're looking outward from the spot within the disk of the Milky Way toward its outer edge, and the stars are far less dense than when you look inward toward Sagittarius.

On a clear dark night, it's easy to see the grand sweep of the Milky Way galaxy and discover all of the deep-sky treasures it possesses.

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