427P/ATLAS

For other comets discovered by the Asteroid Terrestrial-impact Last Alert System, see Comet ATLAS.

427P/ATLAS is a periodic comet and an active asteroid with a 5.65-year orbit around the Sun. It is the second comet discovered by the Asteroid Terrestrial-impact Last Alert System after 478P/ATLAS.^[8]

427P/ATLAS

Comet 427P/ATLAS photographed from the WIYN Observatory (left) and the Hubble Space Telescope (right).[1]
Discovery[2]
Discovered by	Aren Heinze
Discovery site	ATLAS–HKO (T05)
Discovery date	27 September 2017
Designations
MPC designation	P/2017 S5, P/2021 L6
Orbital characteristics[3][4]
Epoch	23 November 2017 (JD 2458080.5)
Observation arc	3.89 years
Earliest precovery date	11 September 2017
Number of observations	438
Aphelion	4.163 AU
Perihelion	2.178 AU
Semi-major axis	3.171 AU
Eccentricity	0.31304
Orbital period	5.646 years
Inclination	11.849°
Longitude of ascending node	252.39°
Argument of periapsis	99.944°
Mean anomaly	20.594°
Last perihelion	19 March 2023[5]
Next perihelion	31 October 2028[5]
TJupiter	3.092
Earth MOID	1.210 AU
Jupiter MOID	1.664 AU
Physical characteristics[6][7]
Mean radius	0.45 ± 0.06 km (0.280 ± 0.037 mi)
Synodic rotation period	~1.4 hours
Geometric albedo	0.06±0.02
Spectral type	(V–R) = 0.43±0.05
Comet total magnitude (M1)	10.7
Comet nuclear magnitude (M2)	15.8

Orbit

The comet orbits within the main asteroid belt at distances between 2.18 AU (326 million km) and 4.16 AU (622 million km) from the Sun.^[3] Studies of its orbital trajectory revealed that it is highly likely a member of the Theobalda collisional family,^[9] a group of asteroids formed from a large, shattered parent body about 7 million years ago.^[10] The main-belt comets 455P/PANSTARRS and 483P/PANSTARRS also belong to this group.

Physical characteristics

Like most of the main-belt comets, the observed activity from 427P/ATLAS is driven by the sublimation of water ice on its surface, which its mass loss rate is estimated to be about ~5.0±3.0 kg/sec^-1 during its perihelion in 2017.^[11]

Photometric observations from the Lisnyky Observatory showed that this comet has some notable instability of color, likely caused by the injection of fresh material to its coma.^[6]

Observations from the Hubble Space Telescope in 2019 had determined that its nucleus has an effective radius of 0.450±0.060 meters, assuming a geometric albedo of 0.06±0.02.^[7][11]