© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.

C/2021 A1 (Leonard) at perigee

Dominic Ford, Editor
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Comet C/2021 A1 (Leonard) will make its closest approach to the Earth, at a distance of 0.23 AU.

From Fairfield the 2021–2022 apparition of C/2021 A1 (Leonard) will progress as follows:

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12 Dec 2021 – C/2021 A1 (Leonard) at perigee
03 Jan 2022 – C/2021 A1 (Leonard) at perihelion
21 Nov 2021Canes VenaticiVisible from 02:29 until 05:36
Highest at 05:36, 56° above E horizon
23 Nov 2021Canes VenaticiVisible from 02:30 until 05:38
Highest at 05:38, 56° above E horizon
25 Nov 2021Canes VenaticiVisible from 02:30 until 05:40
Highest at 05:40, 56° above E horizon
27 Nov 2021Canes VenaticiVisible from 02:31 until 05:42
Highest at 05:42, 56° above E horizon
29 Nov 2021Coma BerenicesVisible from 02:35 until 05:44
Highest at 05:44, 55° above E horizon
01 Dec 2021Canes VenaticiVisible from 02:44 until 05:46
Highest at 05:46, 53° above E horizon
03 Dec 2021BootesVisible from 03:00 until 05:48
Highest at 05:48, 50° above E horizon
05 Dec 2021BootesVisible from 03:28 until 05:49
Highest at 05:49, 44° above E horizon
07 Dec 2021BootesVisible from 04:12 until 05:51
Highest at 05:51, 36° above E horizon
09 Dec 2021Serpens CaputVisible from 05:20 until 05:53
Highest at 05:53, 24° above E horizon
11 Dec 2021OphiuchusNot observable
13 Dec 2021OphiuchusNot observable
15 Dec 2021SagittariusNot observable
17 Dec 2021SagittariusNot observable
19 Dec 2021SagittariusNot observable
21 Dec 2021MicroscopiumNot observable
23 Dec 2021MicroscopiumNot observable
25 Dec 2021MicroscopiumNot observable
27 Dec 2021MicroscopiumNot observable
29 Dec 2021Piscis AustrinusNot observable
31 Dec 2021Piscis AustrinusNot observable

A more detailed table of C/2021 A1 (Leonard)'s position on each night is available here. A diagram of the orbit of C/2021 A1 (Leonard) is available here.

Finder chart

The chart below shows the path of C/2021 A1 (Leonard) over the course of its apparition, as calculated from the orbital elements published by the Minor Planet Center (MPC). It is available for download, either on dark background, in PNG, PDF or SVG formats, or on a light background, in PNG, PDF or SVG formats. It was produced using StarCharter.

Comet brightnesses

Comets are intrinsically highly unpredictable objects, since their brightness depends on the scattering of sunlight from dust particles in the comet's coma and tail. This dust is continually streaming away from the comet's nucleus, and its density at any particular time is governed by the rate of sublimation of the ice in the comet's nucleus, as it is heated by the Sun's rays. It also depends on the amount of dust that is mixed in with that ice. This is very difficult to predict in advance, and can be highly variable even between successive apparitions of the same comet.

In consequence, while the future positions of comets are usually known with a high degree of confidence, their future brightnesses are not. For most comets, we do not publish any magnitude estimates at all. For the few comets where we do make estimates, we generally prefer the BAA's magnitude parameters to those published by the Minor Planet Center, since they are typically updated more often.

Based on the magnitude parameters published for this comet by the BAA Comet Section, we estimate that it may be around mag 4 at perigee. This estimate is based on observations that the BAA has received from amateur astronomers, assuming that its current level of activity will remain constant.

The comet's position at perihelion will be:

Object Right Ascension Declination Constellation Magnitude
Comet C/2021 A1 (Leonard) 17h06m10s 1°28'S Ophiuchus 3.6

The coordinates are given in J2000.0.

The sky on 12 December 2021
Twilight ends
Twilight begins

8-day old moon
Waxing Gibbous


8 days old

Rise Culm. Set
Mercury 07:51 12:17 16:44
Venus 09:37 14:16 18:54
Moon 13:09 19:21 01:43
Mars 05:25 10:14 15:04
Jupiter 11:08 16:23 21:37
Saturn 10:20 15:15 20:10
All times shown in EST.


This event was automatically generated on the basis of orbital elements published by the Minor Planet Center (MPC) , and is updated whenever new elements become available. It was last updated on 20 Sep 2022.

Image credit

© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.






Color scheme