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

C/2020 S3 (Erasmus) at perihelion

Dominic Ford, Editor
From the Comets feed

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Comet C/2020 S3 (Erasmus) will make its closest approach to the Sun, at a distance of 0.40 AU.

From Ashburn the 2020–2021 apparition of C/2020 S3 (Erasmus) will progress as follows:

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18 Nov 2020 – C/2020 S3 (Erasmus) at perigee
12 Dec 2020 – C/2020 S3 (Erasmus) at perihelion
21 Nov 2020VirgoNot observable
23 Nov 2020VirgoNot observable
25 Nov 2020VirgoNot observable
27 Nov 2020HydraNot observable
29 Nov 2020LibraNot observable
01 Dec 2020LibraNot observable
03 Dec 2020LibraNot observable
05 Dec 2020LibraNot observable
07 Dec 2020LibraNot observable
09 Dec 2020ScorpiusNot observable
11 Dec 2020ScorpiusNot observable
13 Dec 2020OphiuchusNot observable
15 Dec 2020OphiuchusNot observable
17 Dec 2020OphiuchusNot observable
19 Dec 2020OphiuchusNot observable
21 Dec 2020SagittariusNot observable
23 Dec 2020SagittariusNot observable
25 Dec 2020SagittariusNot observable
27 Dec 2020SagittariusNot observable
29 Dec 2020SagittariusNot observable
31 Dec 2020ScutumNot observable

A more detailed table of C/2020 S3 (Erasmus)'s position on each night is available here. A diagram of the orbit of C/2020 S3 (Erasmus) is available here.

At the moment of perihelion it will not be readily observable since it will be very close to the Sun, at a separation of only 12° from it.

Finder chart

The chart below shows the path of C/2020 S3 (Erasmus) 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 5 at perihelion. 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/2020 S3 (Erasmus) 16h23m00s 22°44'S Scorpius 5.4

The coordinates are given in J2000.0.

The sky on 12 December 2020
Twilight ends
Twilight begins

27-day old moon
Waning Crescent


27 days old

Rise Culm. Set
Mercury 07:07 11:47 16:28
Venus 05:17 10:19 15:22
Moon 04:44 10:07 15:22
Mars 13:27 19:57 02:26
Jupiter 09:56 14:47 19:38
Saturn 09:59 14:51 19:43
All times shown in EST.


Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.


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 27 Nov 2021.

Image credit

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






Color scheme