C/2019 Y4 (ATLAS)

C/2019 Y4 (ATLAS)
	C/2019 Y4 (ATLAS) imaged on March 14, 2020
Discovery
Discovered by	Asteroid Terrestrial-impact Last Alert System (ATLAS)
Discovery date	December 28, 2019
Designations
Alternative designations	C/2019 Y4-A; C/2019 Y4-B; C/2019 Y4-C; C/2019 Y4-D; C/2019 Y4-E
Orbital characteristics
Epoch	March 7, 2020; (JD 2458915.5)
Observation arc	115 days
Number of; observations	1250
Aphelion	660.9626±3.2491 AU
Perihelion	0.2528 AU
Semi-major axis	330.6077±1.6252 AU
Eccentricity	0.99924
Orbital period	6011.43±44.33 yr
Inclination	45.3839°
Longitude of; ascending node	120.5721°
Argument of; periapsis	177.4084°
Last perihelion	May 31, 2020
TJupiter	0.454
Earth MOID	0.631177 AU (94,422,700 km)
Jupiter MOID	1.39373 AU
Comet total; magnitude (M1)	9.9±0.9
Comet nuclear; magnitude (M2)	13.1±0.7

C/2019 Y4 (ATLAS) (or Comet ATLAS) was a comet with a near-parabolic orbit discovered by the ATLAS survey on December 28, 2019.^[3] Early predictions based on the brightening rate suggested that the comet could become as bright as magnitude 0 matching the brightness of Vega.^[4] It received widespread media coverage due to its dramatic increase in brightness and orbit similar to the Great Comet of 1844, but on March 22, 2020, the comet started disintegrating.^[5]^[6] Such fragmentation events are very common for Kreutz Sungrazers. The comet continues to fade and did not reach naked eye visibility.^[4] By mid-May, comet ATLAS appeared very diffuse even in a telescope. C/2019 Y4 (ATLAS) has not been seen since May 21, 2020.^[7]

C/2019 Y4 (ATLAS) was the brightest on March 30 when it had an apparent magnitude of about 7, but after disintegrating, it continued to fade, until it was last observed on May 21. It is located in the constellation Monoceros but is no longer visible. It reached its nearest point to Earth on May 23 and come to perihelion (closest to the Sun) on May 31.

In April 2020, astronomers reported, on The Astronomer's Telegram, the possible disintegration of Comet ATLAS.^[5]^[6]^[8] The comet has fragmented into at least 4 pieces.^[9]^[10] NASA subsequently reported that the Hubble Space Telescope has identified that there could be as many as roughly "30 fragments on April 20, and 25 pieces on April 23."^[11] The fragmentation may be the result of outgassing causing an increase in the centrifugal force of the comet.

The Solar Orbiter flew through the ion tail of comet ATLAS between May 31 and June 1 and the dust tail on June 6.^[12]^[13]

^ "Small-Body Database Lookup".
^ ^a ^b Cite error: The named reference JPL SBDB was invoked but never defined (see the help page).
^ Dickinson, David (February 25, 2020). "Comet Y4 Atlas in Outburst: First Good Comet for 2020?". Universe Today. Retrieved February 29, 2020.
^ ^a ^b Cite error: The named reference Yoshida was invoked but never defined (see the help page).
^ ^a ^b Cite error: The named reference ATEL13620 was invoked but never defined (see the help page).
^ ^a ^b Steele, I.A.; Smith, R.J.; Marchantn, J. (April 6, 2020). "ATel #13622: C/2019 Y4 ATLAS – confirmation of nuclear change". The Astronomer's Telegram. Retrieved April 7, 2020.
^ Cite error: The named reference COBS was invoked but never defined (see the help page).
^ Lin, Zhang-Yi; et al. (April 13, 2020). "ATel #13629: The fragmentation of comet C/2019 Y4 (Atlas) observed at Lulin observatory". The Astronomer's Telegram. Retrieved April 13, 2020.
^ Philipp Keller (Astrooptik) RC 900mm F/10
^ Ye, Quanzhi; Hui, Man-To (April 21, 2020). "ATel #13651: Continuing Fragmentation of C/2019 Y4 (ATLAS)". The Astronomer's Telegram. Retrieved April 22, 2020.
^ Andreoli, Claire; Villard, Ray; Jewitt, David; Ye, Quanzhi (April 28, 2020). "Hubble Watches Comet ATLAS Disintegrate Into More Than Two Dozen Pieces". www.nasa.gov. National Aeronautics and Space Administration. Retrieved April 28, 2020.
^ Cite error: The named reference ESA20200529 was invoked but never defined (see the help page).
^ Cite error: The named reference NewAtlas was invoked but never defined (see the help page).

[1] "Small-Body Database Lookup".

[JPL_SBDB-2] Cite error: The named reference JPL SBDB was invoked but never defined (see the help page).

[Atlas2020-3] Dickinson, David (February 25, 2020). "Comet Y4 Atlas in Outburst: First Good Comet for 2020?". Universe Today. Retrieved February 29, 2020.

[Yoshida-4] Cite error: The named reference Yoshida was invoked but never defined (see the help page).

[ATEL13620-5] Cite error: The named reference ATEL13620 was invoked but never defined (see the help page).

[AT-20200406b-6] Steele, I.A.; Smith, R.J.; Marchantn, J. (April 6, 2020). "ATel #13622: C/2019 Y4 ATLAS – confirmation of nuclear change". The Astronomer's Telegram. Retrieved April 7, 2020.

[COBS-7] Cite error: The named reference COBS was invoked but never defined (see the help page).

[AT-2299413-8] Lin, Zhang-Yi; et al. (April 13, 2020). "ATel #13629: The fragmentation of comet C/2019 Y4 (Atlas) observed at Lulin observatory". The Astronomer's Telegram. Retrieved April 13, 2020.

[9] Philipp Keller (Astrooptik) RC 900mm F/10

[AT-20200421-10] Ye, Quanzhi; Hui, Man-To (April 21, 2020). "ATel #13651: Continuing Fragmentation of C/2019 Y4 (ATLAS)". The Astronomer's Telegram. Retrieved April 22, 2020.

[11] Andreoli, Claire; Villard, Ray; Jewitt, David; Ye, Quanzhi (April 28, 2020). "Hubble Watches Comet ATLAS Disintegrate Into More Than Two Dozen Pieces". www.nasa.gov. National Aeronautics and Space Administration. Retrieved April 28, 2020.

[ESA20200529-12] Cite error: The named reference ESA20200529 was invoked but never defined (see the help page).

[NewAtlas-13] Cite error: The named reference NewAtlas was invoked but never defined (see the help page).

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