Catch Comet R4 ATLAS as it Nears Earth – Universe Today

The approaching weeks are a good time to catch comet C/2020 R4 ATLAS… when you can.

Trying to do some springtime astronomy? With temperatures warming up within the northern hemisphere in April by means of Could, galaxy season is upon us. At nightfall, the world within the Bowl of Virgo asterism rising within the east is rife with clusters of that spill over into the adjoining constellations of Coma Berenices and Boötes…

However this Could, preserve a watch out for a fuzzball interloper that’s not a galaxy: Comet C/2020 R4 ATLAS.

Found on the evening of September 12th, 2020 by the prolific automated Asteroid Terrestrial Impact Last Alert System (ATLAS) sky survey based mostly in Haleakala (ALTAS-HKO) and Mauna Loa (ATLAS-MLO) Hawaii, R4 ATLAS has confirmed to be an over-achiever. The truth is, it was by no means initially to high +10th magnitude… till a shock outburst in late December 2020 shot it up 100-fold in brightness, from +18th to +13th magnitude. As of scripting this, it sits at about +8th magnitude ‘with a bullet,’ and will high out +7th magnitude this week. Clearly, it is a dynamic comet with tons happening… and another well-placed outburst this week may nudge it into bare eye territory.

The comet reached perihelion on its 957-year orbit on March 1st, 2021 at 1.029 Astronomical Items (AU)(95.7 miles/154 million kilometers) from the Solar. Had the comet dropped by in August, its passage versus the Earth would have been 4 instances nearer.

The trail of comet C/2020 R4 ATLAS by means of the inside photo voltaic system. NASA/JPL

This once-a-millennium orbit additionally signifies that the comet final popped by within the mid-11th century, proper round 1064 AD. Although R4 ATLAS—like most fainter of the pre-telescopic period—went unrecorded, one other well-known denizen of the photo voltaic system did make a historic look only a few years later: Comet 1/P Halley, in 1066 AD. Not solely was this apparition of essentially the most well-known of all comets captured for posterity on the Bayeux Tapestry, however its look was across the identical time because the demise of Harold II in the course of the Battle of Hastings and the ascendancy of William the Conqueror (a foul omen for Harold, however a very good one for William).

The Bayeux Tapestry, that includes Comet 1P Halley. Public Area.

The comet ends the month of April within the constellation of Hercules the Hero. Comet R4 ATLAS is now nicely positioned for remark, ending April into early Could excessive within the east within the ‘Spring Realm of the Galaxies’ away from the aircraft of the Milky Method and the ecliptic aircraft at nightfall, getting larger because the evening goes on. Late Could sees the comet excessive to the south at nightfall.

Comet C/2020 R4 ATLAS animation on 17th April

Right here’s a short record of ‘dates with celestial future’ for the comet, month by month:


23 – Passes nearest to the Earth, at 0.464 AU( 43.2 million miles/69.5 million kilometers) distant.

23 – Crosses into the constellation of Corona Borealis, the Northern Crown.

25 – Passes lower than one diploma from the +4th magnitude star Theta Coronae Borealis.

26 – Crosses into the constellation of Boötes the Herdsman.

27 – Reaches opposition, at 180 levels elongation from the Solar.

30 – Crosses into the constellation of Canes Venatici the Searching Canines.

The celestial path of Comet C/2020 R4 ATLAS, from April 20th by means of June 1st. Credit score: Starry Night time/Dave Dickinson


1 – Picture-Op: passes simply 5 levels from the +7th magnitude globular cluster Messier 3.

7 – Passes into the constellation Coma Berenices (Berenice’s Hair).

11-12 – Nicks the nook of the constellation Ursa Main (the Nice Bear).

13 – Crosses into the constellation Leo the Lion.


1- Could drop again down beneath +10th magnitude.

From there, Comet C/2020 R4 ATLAS heads again out of the inside photo voltaic system, in direction of a distant aphelion 193 AU (18 billion miles/29 billion kilometers) from the Solar in 2500 AD. That’s virtually 5 instances the distance from the Solar to Pluto. The comet received’t pay us a go to once more till out in 2978 AD.

The brightness mild curve of comet C/2020 R4 ATLAS. The black dots are based mostly on precise observations. Tailored from Seiichi Yoshida’s Weekly Information About Bright Comets.

Will R4 ATLAS brighten or fizzle? You simply by no means know with comets. Whereas +8th magnitude places R4 ATLAS in binocular territory, we’ve additionally bought the waxing Moon reaching Full on April 2 to cope with. Hunt for R4 Atlas the way in which you’ll a reasonably shiny globular cluster… sweep the suspect discipline with binoculars or a telescopic wide-field of view, till a fuzzy patch turns into obvious. Not like a globular cluster, nonetheless, a comet like R4 ATLAS will stubbornly refuse to resolve into particular person stars upon focusing in. This contrasting comparability was considered one of 18th century comet hunter Charles Messier’s legendary inspirations for drawing up his first catalog of deep-sky objects, as a means of marking the ‘false comets’ of the sky.

If skies are clear, be sure you take a look at Comet C/2020 R4 ATLAS, one of many first good comets of 2021.

Lead picture: Comet C/2020 R4 ATLAS from April 11th, 2021 courtesy of Michael Jäger.

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