Not since Comet 46P/Wirtanen handed close to the Pleiades star cluster in December 2018 has a naked-eye comet graced the night time sky. That will quickly change. On December 28, 2019, astronomers with the automated Asteroid Terrestrial-impact Last Alert System (ATLAS) survey found a 20th-magnitude comet in Ursa Main that was subsequently named Comet ATLAS (C/2019 Y4).
As soon as an inexpensive orbit was decided, Comet ATLAS proved a detailed match to the Great Comet of 1844 (C/1844 Y1). Each have intervals round four,000 years, method inside zero.25 astronomical unit (a.u.), or 37.four million kilometers, of the Solar at perihelion, and are inclined 45° to the ecliptic. These and different orbital similarities have been robust sufficient to conclude that each objects have been fragments of a single, a lot bigger comet that broke aside about 5,000 years in the past. For all we all know there could also be further fragments en route for future appearances.
As a result of the Nice Comet reached 2nd magnitude and grew a 10° tail in January 1845 many people questioned if its sibling could be able to doing the identical. The reply is a certified “sure.” However one factor is for certain — the comet is brightening exponentially.
A Brightening Comet
Again on February 16th, Comet Atlas was a 14th-magnitude wisp 30″ throughout and barely brighter than the sky background by way of my 15-inch telescope. Three weeks afterward March sixth the coma had grown to about 5′ and grow to be extra compact with a magnitude of 11. By mid-March I snared it with a pair of 10×50 binoculars at magnitude 9 from a dark-sky website. Different observers have reported the same speedy uptick.
How Vivid Will Comet ATLAS Be?
Whereas a hundredfold improve in brightness in a month makes a comet lover’s coronary heart palpitate, it may additionally imply that the comet’s unstable ices are quickly vaporizing because it nears the Solar. As soon as these supplies are depleted some astronomers anticipate Comet ATLAS’s brightness curve to flatten out, a standard prevalence in comets which have not often or by no means come near the Solar earlier than. Lengthy-period comets that method inside 1 a.u. of our star have been identified to separate aside, disintegrate, and disappear. Comet ISON (C/2012 S1) gives a traditional instance. Shortly earlier than its November 2013 perihelion, the comet crumbled right into a cloud of mud and ice, dashing hopes for the spectacle so many people had anticipated.
In line with NASA’s JPL Horizons the comet may attain magnitude –5, exceeding Venus in brightness at perihelion on Might 31st. As a result of it would lie 13° southwest of the Solar at the moment, it could be potential to see the item in broad daylight with a correctly shielded telescope.
That prediction could also be overly optimistic nonetheless. In a March 19th discover from the Central Bureau for Astronomical Telegrams (CBAT), Director Daniel Inexperienced utilized a components based mostly on the habits of earlier long-period, Solar-hugging comets and derived a extra conservative peak magnitude of –zero.three.
It is excellent news both approach. In each predictions Comet ATLAS will attain naked-eye brightness in mid-Might earlier than it is misplaced within the photo voltaic glare. The JPL Horizons components predicts a peak magnitude between 1 and a pair of, whereas Inexperienced anticipates that quantity to be between 2 and three. Through the first half of Might the comet will seem low within the night sky at nightfall and early dusk because it tracks by way of Perseus. Binoculars ought to reveal a vivid, strongly condensed coma adopted by mud and fuel tails pointing away from the Solar. With slightly luck we’d even see the tail with out optical support.
After rounding the Solar, Comet ATLAS returns to view round June 15th at daybreak in Orion for Southern Hemisphere skywatchers. Initially glowing at magnitude three or four, the comet will fade shortly — assuming it survives a scorching perihelic encounter!
Methods to See Comet ATLAS
For now, observers within the Northern Hemisphere can observe the comet from Ursa Main by way of Camelopardalis with a 6-inch or bigger telescope. Whereas seen in binoculars the comet remains to be fairly diffuse and takes some effort to see. That ought to change quickly.
In a telescope, Comet ATLAS exhibits a big, diffuse coma with a small, extra compact knot on the middle dotted with a faint, starlike nucleus. You probably have a Swan band filter, which reinforces carbon emissions from gas-rich comets, you will discover that Comet ATLAS responds properly. I famous a definite improve within the comet’s distinction and visibility by way of the filter this month.
And what would comet-watching be with no picturesque “deep-sky drive-by” or two? Look ahead to Comet ATLAS to buzz inside a level of the galaxy NGC 2366 on April third and go immediately in entrance of the beautiful open cluster NGC 1545 in Perseus on Might 14th.
The comet stays a circumpolar object for a lot of the U.S. and Europe till about two weeks earlier than perihelion, when finest viewing will likely be in the course of the early night hours. If the comet is very dusty, we’ll probably see a extra spectacular tail as a substitute of a vivid, spiked fuzz ball. Be hopeful, however as at all times on the subject of these fragile objects, mood your expectations.
As Comet ATLAS approaches perihelion, I am going to replace with new maps and knowledge. I would love to listen to what you are seeing and encourage you to share your observations and ideas within the feedback part. All of us want some excellent news proper now given the havoc wrought by the coronavirus. Comets have historically been considered as bearers of malevolence all through a lot of human historical past. In a twist of irony this newest emissary from the distant depths of the photo voltaic system might supply a wanted dose of marvel.