427P/ATLAS
{{short description|Periodic comet and active asteroid}}
{{Use dmy dates|date=June 2025}}
{{For|other comets discovered by the Asteroid Terrestrial-impact Last Alert System|Comet ATLAS (disambiguation){{!}}Comet ATLAS}}
{{Infobox comet
| name = 427P/ATLAS
| image = Shape-Shifting Asteroid with a Comet-like Tail - Noaoann19003a.jpg
| caption = Comet 427P/ATLAS photographed from the WIYN Observatory (left) and the Hubble Space Telescope (right).{{r|noirlab}}
| discovery_ref = {{r|CBET_4434}}
| discoverer = Aren Heinze
| discovery_site = ATLAS–HKO (T05)
| discovery_date = 27 September 2017
| mpc_name = P/2017 S5, P/2021 L6
| designations =
| orbit_ref = {{r|jpldata|mpc1}}
| epoch = 23 November 2017 (JD 2458080.5)
| observation_arc = 3.89 years
| earliest_precovery_date = 11 September 2017
| obs = 438
| perihelion = 2.178 AU
| aphelion = 4.163 AU
| semimajor = 3.171 AU
| period = 5.646 years
| eccentricity = 0.31304
| inclination = 11.849°
| asc_node = 252.39°
| arg_peri = 99.944°
| mean = 20.594°
| tjup = 3.092
| Earth_moid = 1.210 AU
| Jupiter_moid = 1.664 AU
| physical_ref = {{r|Borysenko_2019|Hsieh_2023}}
| mean_radius = {{cvt|0.45|±|0.06|km|mi}}
| spectral_type = (V–R) {{=}} {{val|0.43|0.05}}
| rotation = ~1.4 hours
| albedo = {{val|0.06|0.02}}
| M1 = 10.7
| M2 = 15.8
| last_p = 19 March 2023{{r|Yoshida}}
| next_p = 31 October 2028{{r|Yoshida}}
}}
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.{{r|mpc2}}
Orbit
The comet orbits within the main asteroid belt at distances between {{convert|2.18|AU|e6km|abbr=unit}} and {{convert|4.16|AU|e6km|abbr=unit}} from the Sun.{{r|jpldata}} Studies of its orbital trajectory revealed that it is highly likely a member of the Theobalda collisional family,{{r|Novaković_2018}} a group of asteroids formed from a large, shattered parent body about 7 million years ago.{{r|Xin_2024}} 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 ~{{val|5.0|3.0}} kg/sec-1 during its perihelion in 2017.{{r|Jewitt_2019}}
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.{{r|Borysenko_2019}}
Observations from the Hubble Space Telescope in 2019 had determined that its nucleus has an effective radius of {{val|0.450|0.060}} meters, assuming a geometric albedo of {{val|0.06|0.02}}.{{r|Hsieh_2023|Jewitt_2019}}
References
{{Reflist|refs=
| author1= S. Borysenko
| author2= A. Baransky
| author3= E. Musiichuk
| title= Photometric observations of ecliptic comet 47P/Ashbrook–Jackson and selected quasi-Hilda and main-belt comets at Kyiv Comet Station (MPC code - 585) in 2017
| journal= Icarus
| year= 2019
| volume= 317
| pages= 44–47
| bibcode= 2019Icar..317...44B
| arxiv= 2005.11143
| doi= 10.1016/j.icarus.2018.07.003 }}
| author1= A. Heinze
| author2= H. Sato
| author3= R. A. Kowalski
| author4= K. Sarneczky
| author5= O. Hanyecz
| author6= J. F. Soulier
| author7= S. Foglia
| author8= L. Buzzi
| author9= P. Miller
| author10= E. Gomez
| author11= R. Holmes
| display-authors= 5
| editor1= D. W. Green
| title= Comet P/2017 S5 (ATLAS)
| url= http://www.cbat.eps.harvard.edu/iau/cbet/004400/CBET004434.txt
| journal= Central Bureau Electronic Telegrams
| date= September 2017
| volume= 4434
| issue= 1
| bibcode= 2017CBET.4434....1S }}
| author1= H. H. Hsieh
| author2= M. Micheli
| author3= M. S. P. Kelley
| author4= M. M. Knight
| author5= N. A. Moskovitz
| author6= J. Pittichová
| author7= S. S. Sheppard
| author8= A. Thirouin
| author9= C. A. Trujillo
| author10= R. J. Wainscoat
| author11= R. J. Weryk
| author12= Q. Ye
| display-authors= 5
| title= Observational Characterization of Main-belt Comet and Candidate Main-belt Comet Nuclei
| url= https://iopscience.iop.org/article/10.3847/PSJ/acbdfe/pdf
| journal= Planetary Science Journal
| year= 2023
| volume= 4
| issue= 3
| pages= 43–65
| bibcode= 2023PSJ.....4...43H
| arxiv= 2302.11689
| doi= 10.3847/PSJ/acbdfe
| doi-access= free }}
| author1= D. C. Jewitt
| author2= Y. Kim
| author3= J. Rajagopal
| author4= S. Ridgway
| author5= R. Kotulla
| author6= W. Liu
| author7= M. Mutchler
| author8= J. Li
| author9= H. Weaver
| author10= S. Larson
| display-authors= 5
| title= Active Asteroid P/2017 S5 (ATLAS)
| journal= The Astronomical Journal
| year= 2019
| volume= 157
| issue= 2
| pages= 1–8
| bibcode= 2019AJ....157...54J
| arxiv= 1812.00060
| doi= 10.3847/1538-3881/aaf563
| doi-access= free }}
| title= 427P/ATLAS – JPL Small-Body Database Lookup
| url= https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=427P
| website= ssd.jpl.nasa.gov
| publisher= Jet Propulsion Laboratory
| access-date= 3 June 2025 }}
| title= 427P/ATLAS Orbit
| url= http://www.minorplanetcenter.net/db_search/show_object?object_id=427P
| publisher= Minor Planet Center
| access-date= 3 June 2025 }}
| title= 478P/ATLAS Orbit
| url= http://www.minorplanetcenter.net/db_search/show_object?object_id=478P
| publisher= Minor Planet Center
| access-date= 3 June 2025 }}
| title= Shape-Shifting Asteroid with a Comet-like Tai
| url= https://noirlab.edu/public/images/noaoann19003a/
| website= NOIRLab
| publisher= National Science Foundation
| date= 31 January 2019
| access-date= 3 June 2025 }}
| author1= B. Novaković
| title= P/2017 S5: Another Active Asteroid Associated with the Theobalda Family
| journal= Research Notes of the American Astronomical Society
| year= 2018
| volume= 2
| issue= 3
| bibcode= 2018RNAAS...2..129N
| arxiv= 1807.08728
| doi= 10.3847/2515-5172/aad412
| doi-access= free }}
| author1= Y. Xin
| author2= J. Shi
| author3= Y. Ma
| title= Research of the family associations of active asteroids in the main belt
| journal= Monthly Notices of the Royal Astronomical Society
| volume= 527
| issue= 4
| year= 2024
| pages= 10309–10334
| bibcode= 2024MNRAS.52710309X
| doi= 10.1093/mnras/stad3883
| doi-access= free }}
| author1= S. Yoshida
| title= 427P/ATLAS
| url= http://www.aerith.net/comet/catalog/0427P/index.html
| website= www.aerith.net
| access-date= 3 June 2025 }}
}}