Objects in your sky: Comets

by Dominic Ford

Below is a list of the brightest few comets that are visible at present.

You are welcome to reproduce the text below for non-profit purposes, providing you credit In-The-Sky.org.

Comet name Mag Constellation Separation
from Sun
Trend Absolute magnitude
last updated
Comet name Mag Constellation Separation
from Sun
Trend Absolute magnitude
last updated
C/2020 R4 (ATLAS)6.7Aquarius25°
Brightening
(peak at mag 6.3 on 13 Mar 2021)
2 Feb 2021
10P/Tempel11.3Capricornus24°
Brightening
(peak at mag 11.0 on 28 Mar 2021)
1 Apr 2018
C/2019 N1 (ATLAS)11.3Octans79°
Fading
(peak at mag 10.7 on 2 Jan 2021)
2 Feb 2021
C/2021 A2 (NEOWISE)12.4Auriga109°
Fading
(peak at mag 10.7 on 2 Feb 2021)
2 Feb 2021
C/2019 L3 (ATLAS)13.2Cassiopeia71°
Brightening
2 Feb 2021
C/2017 T2 (PANSTARRS)13.4Scorpius69°
Fading
2 Oct 2020
88P/Howell13.4Pisces30°
Fading
1 Apr 2018
C/2020 S3 (Erasmus)13.4Aquarius11°
Fading
5 Jan 2021
C/2020 M3 (ATLAS)13.5Auriga113°
Fading
2 Feb 2021
110P/Hartley14.1Pisces43°
Brightening
29 Feb 2012
398P/Boattini14.2Gemini123°
Fading
3 Feb 2021
4P/Faye14.3Aquarius16°
Brightening
14 Sep 2017
141P/Machholz14.4Orion95°
Fading
1 Apr 2018
246P/NEAT14.4Sagittarius61°
Brightening
(peak at mag 13.5 on 18 Jun 2021)
3 Jun 2020
15P/Finlay14.5Sagittarius53°
Brightening
(peak at mag 8.4 on 8 Jul 2021)
14 Sep 2017
C/2018 N2 (ASASSN)14.7Draco97°
Fading
2 Oct 2020
C/2017 K2 (PANSTARRS)14.7Lyra73°
Brightening
2 Feb 2021
67P/Churyumov-Gerasimenko14.8Capricornus25°
Brightening
1 Apr 2018
C/2018 F4 (PANSTARRS)15.2Cetus43°
Fading
2 Oct 2020
74P/Smirnova-Chernykh15.3Capricornus24°
Brightening
(peak at mag 14.6 on 6 Aug 2021)
29 Feb 2012
16P/Brooks15.4Aquarius16°
Brightening
(peak at mag 15.1 on 18 Apr 2021)
14 Sep 2017
58P/Jackson-Neujmin15.5Monoceros120°
Fading
2 Sep 2020
52P/Harrington-Abell15.7Pisces40°
Brightening
Unknown
22P/Kopff15.8Leo172°
Brightening
1 Apr 2018
117P/Helin-Roman-Alu15.9Virgo129°
Brightening
(peak at mag 15.2 on 19 May 2021)
16 Oct 2014

The position of each comet is calculated from orbital elements published by the Minor Planet Center (MPC).

The brightnesses of comets are estimated from magnitude parameters published by the BAA Comet Section, where these are available. These are computed from the observations they receive from amateur astronomers.

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.

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