C/2020 R4 (ATLAS)

C/2020 R4 (ATLAS)

Comet C/2020 R4 (ATLAS) photographed by the Zwicky Transient Facility on 2 April 2021.
Discovery[1]
Discovery site	ATLAS–MLO (T08)
Discovery date	12 September 2020
Designations
Alternative designations	CK20R040
Orbital characteristics[2]
Epoch	13 March 2021 (JD 2459286.5)
Observation arc	1.50 years
Earliest precovery date	29 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°
Longitude of ascending node	323.27°
Argument of periapsis	46.708°
Mean anomaly	0.011°
Last perihelion	1 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).

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]

• C/2020 R4 at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit viewer · Orbit parameters · Physical parameters
• C/2020 R4 (ATLAS) at Gideon van Buitenen's website.
• C/2020 R4 (ATLAS) at Seiichi Yoshida's website

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