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NGC 4861
NGC 4861
	Hubble Space Telescope image of NGC 4861, taken using the Advanced Camera for Surveys
Observation data (J2000 epoch)
Constellation	Canes Venatici
Right ascension	12h 59m 02.340s
Declination	+34° 51′ 33.98″
Redshift	0.002785
Heliocentric radial velocity	835
Distance	34.77 ± 15.99 Mly (10.662 ± 4.903 Mpc)
Group or cluster	Virgo Cluster
Apparent magnitude (V)	12.32
Apparent magnitude (B)	12.90
Characteristics
Type	SB(s)m; Im/BCD
Apparent size (V)	0.797′ × 0.692′
Other designations
	Arp 266, UGC 8098, MCG+06-29-003, PGC 44536

NGC 4861, also known as Arp 266, is a galaxy in the constellation Canes Venatici. It was discovered by William Herschel on May 1, 1785.^[4]

Morphological classification of NGC 4861 has proved relatively difficult. Its mass, size, and rotational velocity are consistent with it being a spiral galaxy. However, due to its highly irregular shape, it may also be classified as a dwarf irregular galaxy.^[5] In fact, since dwarf galaxies are less massive and have lower gravitational potentials, gases and other material for star formation can move within them much faster, causing the galaxy to become a specific type of starburst galaxy, called a blue compact dwarf galaxy.^[5]^[3] It has also been described as a "comet-like" galaxy due to its resemblance to a comet.^[6]

Two ultraluminous X-ray sources (ULXs) have been found within NGC 4861. The first, NGC 4861 X1, is associated with a dense H II region. The second, NGC 4861 X2, seems to be within a small star cluster near the "comet head" of NGC 4861. Assuming it is a star cluster, it has a mass of 400±80 M_☉ and an age of 5 million years. Compared to other star clusters with which ULXs are associated, its mass is quite low.^[6]

References

^ ^a ^b ^c Skrutskie, Michael F.; Cutri, Roc M.; Stiening, Rae; Weinberg, Martin D.; Schneider, Stephen E.; Carpenter, John M.; Beichman, Charles A.; Capps, Richard W.; Chester, Thomas; Elias, Jonathan H.; Huchra, John P.; Liebert, James W.; Lonsdale, Carol J.; Monet, David G.; Price, Stephan; Seitzer, Patrick; Jarrett, Thomas H.; Kirkpatrick, J. Davy; Gizis, John E.; Howard, Elizabeth V.; Evans, Tracey E.; Fowler, John W.; Fullmer, Linda; Hurt, Robert L.; Light, Robert M.; Kopan, Eugene L.; Marsh, Kenneth A.; McCallon, Howard L.; Tam, Robert; Van Dyk, Schuyler D.; Wheelock, Sherry L. (1 February 2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. ISSN 0004-6256. S2CID 18913331.
^ ^a ^b ^c ^d "NED results for object NGC 4861". National Aeronautics and Space Administration / Infrared Processing and Analysis Center. Retrieved 4 February 2017.
^ ^a ^b "NGC 4861". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 4 February 2017.
^ Courtney Seligman. "New General Catalog Objects: NGC 4500 - 4599". Retrieved 4 February 2017.
^ ^a ^b "Starbirth with a chance of winds?". www.spacetelescope.org. Retrieved 4 February 2017.
^ ^a ^b Ela, M Ozdogan; Akyuz, A.; Aksaker, N.; Avdan, S.; Oralhan, I Akkaya; Vinokurov, A.; Allak, S.; Solovyeva, Y.; Atapin, K.; Bizyaev, D. (2021). "Optical counterparts of ULXs in two dwarf galaxies: NGC 4861 and NGC 4449". Monthly Notices of the Royal Astronomical Society. 505: 771–782. arXiv:2105.02302. doi:10.1093/mnras/stab1321.