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

Comet C/2021 P4 (ATLAS) passes perihelion

Dominic Ford, Editor
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The sky at

Comet C/2021 P4 (ATLAS) will make its closest approach to the Sun on 30 July, at a distance of 1.08 AU.

From Fairfield on the day of perihelion it will not be readily observable since it will be very close to the Sun, at a separation of only 20° from it.

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The events that comprise the 2022 apparition of C/2021 P4 (ATLAS) are as follows:

Date Event
30 Jul 2022Comet C/2021 P4 (ATLAS) passes perihelion

The table below lists the times when C/2021 P4 (ATLAS) will be visible from Fairfield day-by-day through its apparition:

Date Constellation Comet visibility
09 Jul 2022CancerNot observable
11 Jul 2022CancerNot observable
13 Jul 2022CancerNot observable
15 Jul 2022LeoNot observable
17 Jul 2022LeoNot observable
19 Jul 2022LeoNot observable
21 Jul 2022LeoNot observable
23 Jul 2022LeoNot observable
25 Jul 2022LeoNot observable
27 Jul 2022LeoNot observable
29 Jul 2022LeoNot observable
31 Jul 2022LeoNot observable
02 Aug 2022LeoNot observable
04 Aug 2022LeoNot observable
06 Aug 2022LeoNot observable
08 Aug 2022LeoNot observable
10 Aug 2022SextansNot observable
12 Aug 2022SextansNot observable
14 Aug 2022SextansNot observable
16 Aug 2022SextansNot observable
18 Aug 2022SextansNot observable

A more detailed table of C/2021 P4 (ATLAS)'s position on each night is available here. A diagram of the orbit of C/2021 P4 (ATLAS) is available here.

Finder chart

The chart below shows the path of C/2021 P4 (ATLAS) 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 10 on 30 July 2022. This estimate is based on observations that the BAA has received from amateur astronomers, assuming that its current level of activity will remain constant.

You will probably require a telescope to see this comet. It is unlikely to be visible through bird-watching binoculars, and even less likely to be visible to the unaided eye.

The comet's position at perihelion will be:

Object Right Ascension Declination Constellation Magnitude
Comet C/2021 P4 (ATLAS) 09h59m30s 14°12'N Leo 10.3

The coordinates are given in J2000.0.

The sky on 30 Jul 2022

The sky on 30 July 2022
Twilight ends
Twilight begins

2-day old moon
Waxing Crescent


2 days old

Rise Culm. Set
Mercury 06:57 13:57 20:57
Venus 03:56 11:24 18:53
Moon 07:16 14:34 21:40
Mars 00:22 07:20 14:18
Jupiter 22:44 04:54 11:04
Saturn 20:55 02:03 07:11
All times shown in EDT.


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 Mar 2023.

Image credit

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






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