C/2020 R4 (ATLAS)

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C/2020 R4 (ATLAS)
C2020R4 2021-04-02 image ZTF-sso-438-zr-size-9.0arcmin.png
Comet C/2020 R4 (ATLAS) photographed by the Zwicky Transient Facility on 2 April 2021.
Discovery [1]
Discovery site ATLAS–MLO (T08)
Discovery date12 September 2020
Designations
CK20R040
Orbital characteristics [2]
Epoch 13 March 2021 (JD 2459286.5)
Observation arc 1.50 years
Earliest precovery date29 August 2020
Number of
observations		2,399
Aphelion 192.40 AU
Perihelion 1.029 AU
Semi-major axis 96.713 AU
Eccentricity 0.98936
Orbital period ~950 years
Inclination 164.46°
323.27°
Argument of
periapsis 		46.708°
Mean anomaly 0.011°
Last perihelion1 March 2021
Next perihelion~2970s
TJupiter –1.155
Earth MOID 0.117 AU
Jupiter MOID 0.023 AU
Comet total
magnitude (M1)		12.8
Comet nuclear
magnitude (M2)		15.6

C/2020 R4 (ATLAS) is a long-period comet with a roughly 950-year orbit around the Sun. It is one of many comets discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS).

Contents

Observational history

On 12 September 2020, James E. Robinson reported the discovery of the comet taken by the ATLAS facility of the Mauna Loa Observatory in Hawaii, [1] where he noted that a coma about 10 arcseconds wide is present at the time. Precovery images as early as 29 August were later found. [1] Initially, it was predicted to become only a faint comet, until an unexpected outburst in December 2020 had increased its brightness by a hundred-fold, from magnitude 18 to 13. [3]

The comet reached perihelion on 1 March 2021. By 13 March, it was an 8th-magnitude object within the constellation Aquila. [4]

During its outbound flight, three outbursts were recorded between 20 April and 6 May 2021, with the first event being the strongest of the outbursts observed. [5] Spectral and morphological analysis taken shortly after the first outburst on 22 April revealed that its nucleus has one active area producing jets of material asymmetrically to its inner coma. [6] Its closest approach to Earth occurred on the next day, at a distance of 0.464 AU (69.4 million km). [2] [3]

References

  1. 1 2 3 "MPEC 2020-S33: Comet C/2020 R4 (ATLAS)". www.minorplanetcenter.net. Minor Planet Center. 16 September 2020.
  2. 1 2 "C/2020 R4 (ATLAS) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory . Retrieved 12 September 2025.
  3. 1 2 D. Dickinson (21 April 2021). "Catch Comet R4 ATLAS as it Nears Earth". Universe Today. Retrieved 13 September 2025.
  4. ↑ M. Armstrong (13 March 2021). "Observe Comet 2020 R4 (ATLAS) as it wings its way towards Earth". Astronomy Now. Retrieved 13 September 2025.
  5. ↑ M. S. P. Kelley; T. Lister; et al. (2021). "Three Outbursts of Comet C/2020 R4 (ATLAS)". The Astronomer's Telegram. 14618. Bibcode:2021ATel14618....1K.
  6. ↑ F. Manzini; P. Ochner; V. Oldani; L. R. Bedin (2021). "Spectra and morphological structures in the inner coma of comet C/2020 R4 (ATLAS)". The Astronomer's Telegram. 14585. Bibcode:2021ATel14585....1M.
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