Comet A1 Leonard to Brighten in December

Now’s the time to start out monitoring Comet C/2021 A1 Leonard, because it begins its crack of dawn dive sunward.

The times following New 12 months’s 2021 noticed a comet discovery with possible. At the night time of January 3rd, precisely twelve months to the day previous to perihelion, astronomer Gregory J. Leonard running on the Mount Lemmon Observatory close to Tucson Arizona found out the primary long-period comet of the 12 months, C/2021 A1 Leonard. Shining at magnitude +19 and 5 Astronomical Devices (AU) far-off (concerning the distance of Jupiter from the Solar) on the time of discovery, early indications hinted that comet A1 Leonard would possibly end up to be one thing particular, come the tip of 2021.

On an 80,000 12 months orbit inbound, Comet A1 Leonard is due for ejection from the sun gadget after its perihelion passage early subsequent 12 months. The comet reached aphelion 3,500 AU far-off within the Oort Cloud about 35,000 years in the past. The impending perihelion cross on January 3rd, 2022 can be 0.62 AU from the Solar, inside to the orbit of Venus.

The orbit of Comet A1 Leonard, set for its closest passage close to Earth.

Be mindful, A1 Leonard could also be a seasoned long-term customer to the internal sun gadget with a possible to over-perform because it nears the Solar. Present predictions have the comet attaining +4th magnitude, and it’ll flirt with bare eye brightness. The comet passes simply 0.233 AU (21.7 million miles or 34.9 million kilometers) from the Earth on December twelfth, any other plus.

Incessantly, dynamically new comets show off a burst of task as they means the internal sun gadget for the primary time, warmth up, and sublimate their outer layers. This will additionally faux out observers to start with, resulting in overly constructive predictions. All of us take into account the Nice Comet that wasn’t all through the 1973 passage of C/1973 E1 Kohoutek. A comet equivalent to A1 Leonard has survived a perihelion passage ahead of with out disintegrating… regardless that this one can be its ultimate.

Getting brighter… Comet A1 Leonard from November thirteenth. Credit score and copyright: Hisayoshi Kato.

Lately, A1 Leonard is situated top at crack of dawn for northern hemisphere observers within the constellation Canes Venatici, and starts the plunge sunward all through the primary part of the month. We in reality pass the aircraft of the comet’s orbit on December 8th, and the comet might show off a pointy ‘anti-tail’ spike sunward round this time.

Some other intriguing impact might also come into play all through the December apparition of Comet A1 Leonard. The the Solar-Earth-Comet phase-angle for the tail will sit down at more than 120 levels from December 9th to December 22nd, and achieve a most of 160 levels on December 14th simply after it passes closest to the Earth on December 12th. This units up stipulations ultimate for a imaginable surge in brightness, including the brightness of the tail to the coma of the comet itself.

Comet A1 Leonard from October thirtieth. Symbol credit score and copyright: Zlatko Orbanic.

It’s all the time tricky to grasp precisely what comets will do. The planet Venus in reality passes during the tail of Comet A1 Leonard on December nineteenth, in all probability making a Venusian meteor bathe within the procedure. Lately, most effective JAXA’s Akatsuki project in on-hand and energetic in orbit round Venus.

Sadly, the night time apparition for Comet A1 Leonard can be a bashful one after it flips from morning to the nightfall sky round December fifteenth. For northern hemisphere observers the comet remains low within the nightfall. Southern hemisphere audience will, then again, get a greater view because the comet fades, receding within the route of the constellation of Piscis Austrinus in early 2022.

The celestial trail of Comet A1 Leonard in December 2021. Credit score: Starry Night time

Listed here are some key celestial dates with future for Comet A1 Leonard (be aware ‘shut’ way inside a point, until differently indicated):


28-Crosses into Coma Berenices

The crack of dawn trail of the comet in early December. Credit score: Starry Night time.


1-Crosses into Canes Venatici

3-Photograph op: passes very close to the globular cluster Messier 3

4-Crosses into Boötes

6-Passes 4 levels from the brilliant big name Arcturus

8-Orbit edge-on as observed from Earth

9-Crosses into Serpens Caput

10-Crosses into Hercules

11-Crosses into Ophiuchus

12-Crosses the celestial equator southward, and passes 0.233 AU (34.9 million km) from the Earth, shifting part a point (the span of a Complete Moon) in step with hour.

13-Flips over from the morning to night time sky, and might best out at +4th magnitude.

14-Passes close to +3.3 magnitude big name Nu Ophiuchi, and into Serpens Cauda

14-Transits Messier 16, and passes 15 levels from the Solar.

15-Crosses the galactic aircraft southward

15-In brief crosses into Scutum, passes close to comet 252P LINEAR, passes 1.5 levels from Messier 17, and crosses into Sagittarius

16-Passes close to the celebs: +3.5 magnitude Xi^2 Sagittarii, +3.8 Omicron Sagittarii and +2.8 Albaldah, and crosses the ecliptic southward

17-Passes 5 levels from Venus

18-Passes simply 0.028 AU (4.2 million km) from Venus

21-Crosses into Microscopium

30-Passes into Piscis Austrinus

The nightfall view of Comet A1 Leonard for the ultimate part of December, as appear from South Africa. Credit score: Starry Night time.


3-Reaches perihelion at 0.62 AU from the Solar


1-Drops go into reverse under +10th magnitude

As you’ll be able to see, mid-December is a hectic one for Comet A1 Leonard, because it nears the bustling galactic aircraft.

The sunshine curve of Comet A1 Leonard, with observations (black dots) as opposed to perihelion (red line). Tailored from Seiichi Yoshida’s Weekly Knowledge About Vibrant Comets.

Binoculars are your best possible good friend with regards to sweeping up a comet: merely scan the suspect goal box, and search for the faint fuzzy that refuses to snap into focal point. At this degree, comets incessantly appear to be globular clusters that refuse to get to the bottom of into particular person stars. ‘If’ Comet A1 Leonard over-performs and breaks into bare eye territory, issues may get in reality fascinating. Like Comet F3 NEOWISE, A1 Leonard would then have the prospective to pose with foreground items within the crack of dawn, making for a in reality photogenic comet.

Plan on braving the morning December chilly to seize sight of Comet A1 Leonard at crack of dawn.

Lead symbol credit score: Comet A1 Leonard close to the galaxy NGC 4395 in mid-November. Credit score and copyright: Michael Jäger.

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