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

Comet C/2023 A3 (Tsuchinshan-ATLAS) passes perihelion

Dominic Ford, Editor
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Comet C/2023 A3 (Tsuchinshan-ATLAS) will make its closest approach to the Sun on 27 September, at a distance of 0.39 AU.

From Washington on the day of perihelion it will not be observable – it will reach its highest point in the sky during daytime and will be no higher than 7° above the horizon at dawn.

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The events that comprise the 2024 apparition of C/2023 A3 (Tsuchinshan-ATLAS) are as follows:

Date Event
27 Sep 2024Comet C/2023 A3 (Tsuchinshan-ATLAS) passes perihelion
12 Oct 2024Comet C/2023 A3 (Tsuchinshan-ATLAS) passes perigee

The table below lists the times when C/2023 A3 (Tsuchinshan-ATLAS) will be visible from Washington day-by-day through its apparition:

Date Constellation Comet visibility
06 Sep 2024SextansNot observable
08 Sep 2024SextansNot observable
10 Sep 2024SextansNot observable
12 Sep 2024SextansNot observable
14 Sep 2024SextansNot observable
16 Sep 2024SextansNot observable
18 Sep 2024SextansNot observable
20 Sep 2024SextansNot observable
22 Sep 2024SextansNot observable
24 Sep 2024SextansNot observable
26 Sep 2024SextansNot observable
28 Sep 2024LeoNot observable
30 Sep 2024LeoNot observable
02 Oct 2024LeoNot observable
04 Oct 2024VirgoNot observable
06 Oct 2024VirgoNot observable
08 Oct 2024VirgoNot observable
10 Oct 2024VirgoNot observable
12 Oct 2024VirgoNot observable
14 Oct 2024VirgoVisible from 19:37 until 19:53
Highest at 19:37, 16° above W horizon
16 Oct 2024Serpens CaputVisible from 19:33 until 20:28
Highest at 19:33, 23° above W horizon

A more detailed table of C/2023 A3 (Tsuchinshan-ATLAS)'s position on each night is available here. A diagram of the orbit of C/2023 A3 (Tsuchinshan-ATLAS) is available here.

Finder chart

The chart below shows the path of C/2023 A3 (Tsuchinshan-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 1 on 27 September 2024. 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/2023 A3 (Tsuchinshan-ATLAS) 10h46m00s 6°04'S Sextans 0.9

The coordinates are given in J2000.0.

The sky on 27 Sep 2024

The sky on 27 September 2024
Twilight ends
Twilight begins

24-day old moon
Waning Crescent


24 days old

Rise Culm. Set
Mercury 07:11 13:16 19:20
Venus 09:55 15:17 20:38
Moon 02:21 09:54 17:18
Mars 00:43 08:02 15:21
Jupiter 23:10 06:26 13:42
Saturn 18:35 00:13 05:50
All times shown in MDT.


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 07 Jun 2024.

Image credit

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





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