Holmberg IX
Dwarf irregular galaxy in the constellation of Ursa Major
Holmberg IX Constellation Ursa Major Right ascension 09h 57m 32.1s Declination +69° 02′ 46″ Distance 12 Mly (3.6 Mpc ) Apparent magnitude (V)16.5 Type dI Apparent size (V)1.41 ± 0.07 Notable features Satellite galaxy of Messier 81 UGC 5336, [B93] 17, DDO 66, 2E 0953.7+6918, 2E 2199, 1ES 0953+69.3, HIJASS J0957+69A, Holmberg IX, [IW2001] H42, [IW2001] P63, K68 62, LEDA 28757, Mailyan 48, MCG+12-10-012, [MI94] Im 62, SPB 118, PGC 28757
Holmberg IX is a dwarf irregular galaxy and a satellite galaxy of M81 , located in the constellation of Ursa Major . It is a Magellanic-type galaxy , similar to the Small Magellanic Cloud , neighbour galaxy to the Milky Way galaxy. The galaxy is named after Erik Holmberg who first described it, though it was originally discovered by Sidney van den Bergh in 1959. Based on the observed age distribution of stars it contains, 20% of its stellar mass formed within the last 200 Myr , making it the youngest nearby galaxy. It is also home to one of two yellow supergiant eclipsing binary systems designated Holmberg IX V1 .
Further reading
Winter, Lisa M.; Mushotzky, Richard F.; Reynolds, Christopher S. (2007). "Elemental Abundances of Nearby Galaxies through High Signal-to-Noise Ratio XMM-Newton Observations of Ultraluminous X-Ray Sources". The Astrophysical Journal . 655 (1): 163– 178. arXiv :astro-ph/0610369 . Bibcode :2007ApJ...655..163W . doi :10.1086/510200 . S2CID 115819754 .
Fabien, Grisé; Pakull, Manfred W.; Motch, Christian (2006-05-12). "The Ultraluminous X-ray Source in Holmberg IX and its Environment". Proceedings of the International Astronomical Union . 1 (S230): 302– 303. arXiv :astro-ph/0603768 . Bibcode :2006IAUS..230..302G . doi :10.1017/S1743921306008519 . S2CID 118995588 .
Makarova, L.; Grebel, E. K.; Karachentsev, I. D.; Dolphin, A. E.; Karachentseva, V. E.; Sharina, M. E.; Geisler, D.; Guhathakurta, P.; et al. (2002). "Tidal dwarfs in the M81 group: the second generation?" . Astronomy and Astrophysics . 396 (2): 473– 487. arXiv :astro-ph/0210235 . Bibcode :2002A& A...396..473M . doi :10.1051/0004-6361:20021426 .
Schulte-Ladbeck, R. E.; Hopp, U. (1987). "The Dwarf Irregular Galaxy Holmberg IX". Mitteilungen der Astronomischen Gesellschaft . 70 : 427. Bibcode :1987MitAG..70..427S .
Bertola, F.; Maffei, P. (1974). "Two Faint Companions to M81". Astronomy and Astrophysics . 32 : 117. Bibcode :1974A& A....32..117B .
Holmberg, E. (1969). "A study of physical groups of galaxies". Arkiv för Astronomi . 5 : 305– 343. Bibcode :1969ArA.....5..305H .
van den Bergh, Sidney (1959). "A catalogue of dwarf galaxies". Publications of the David Dunlap Observatory . 2 (5). University of Toronto : 147. Bibcode :1959PDDO....2..147V .