Comet C/2020 R4 (ATLAS) will make its closest approach to the Sun on 2 March, at a distance of 1.02 AU.
From Cambridge 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.
The events that comprise the 2021 apparition of C/2020 R4 (ATLAS) are as follows:
| Date | Event |
| 02 Mar 2021 | Comet C/2020 R4 (ATLAS) passes perihelion |
The table below lists the times when C/2020 R4 (ATLAS) will be visible from Cambridge day-by-day through its apparition:
| Date | Constellation | Comet visibility |
| 09 Feb 2021 | Aquarius | Not observable |
| 11 Feb 2021 | Aquarius | Not observable |
| 13 Feb 2021 | Aquarius | Not observable |
| 15 Feb 2021 | Aquarius | Not observable |
| 17 Feb 2021 | Aquarius | Not observable |
| 19 Feb 2021 | Aquarius | Not observable |
| 21 Feb 2021 | Aquarius | Not observable |
| 23 Feb 2021 | Aquarius | Not observable |
| 25 Feb 2021 | Aquarius | Not observable |
| 27 Feb 2021 | Aquarius | Not observable |
| 01 Mar 2021 | Aquarius | Not observable |
| 03 Mar 2021 | Capricornus | Not observable |
| 05 Mar 2021 | Capricornus | Not observable |
| 07 Mar 2021 | Capricornus | Not observable |
| 09 Mar 2021 | Capricornus | Not observable |
| 11 Mar 2021 | Capricornus | Not observable |
| 13 Mar 2021 | Capricornus | Not observable |
| 15 Mar 2021 | Aquila | Not observable |
| 17 Mar 2021 | Aquila | Not observable |
| 19 Mar 2021 | Aquila | Not observable |
| 21 Mar 2021 | Aquila | Visible from 05:33 until 05:37 Highest at 05:37, 22° above SE horizon |
A more detailed table of C/2020 R4 (ATLAS)'s position on each night is available here. A diagram of the orbit of C/2020 R4 (ATLAS) is available here.
Finder chart
The chart below shows the path of C/2020 R4 (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.
No estimate for the brightness of comet C/2020 R4 (ATLAS) is currently available.
The comet's position at perihelion will be:
| Object | Right Ascension | Declination | Constellation | Magnitude |
| Comet C/2020 R4 (ATLAS) | 20h40m10s | 11°21'S | Aquarius | 10.0 |
The coordinates are given in J2000.0.
The sky on 2 Mar 2021
| The sky on 2 March 2021 | ||||||||||||||||||||||||||||||||||
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81% 19 days old |
All times shown in EST.
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Source
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 18 Apr 2024.
Image credit
© Andy Roberts 1997. Pictured comet is C/1995 O1 Hale-Bopp.