Messier 81

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
A Hubble Space Telescope (HST) image of Messier 81

Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy. It is in the constellation Ursa Major. It is large. It is about 12 million light-years from Earth. It has an active galactic nucleus (which has a supermassive black hole). For these reasons Messier 81 has been well studied by professional astronomers. The galaxy is large and very bright. This makes it a popular object for amateur astronomers to look at.[1]

Discovery[change | change source]

Messier 81 was first discovered by Johann Elert Bode in 1774.[2] The galaxy is sometimes called "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object. They listed it as Messier 81 in the Messier Catalogue.[2]

Dust emission[change | change source]

Interstellar dust is found in the galaxy's spiral arms. It is connected with star formation areas.[3][4] The hot blue stars that are found in star formation areas heat the dust. The dust is seen as infrared energy that is sent out from these areas.

Supernova[change | change source]

Only one supernova has been seen in Messier 81.[5] The supernova is named SN 1993J. It was discovered on 28 March 1993 by F. Garcia in Spain.[6] At the time, it was the second brightest supernova seen in the 20th century.[7]

M81 Group[change | change source]

M81 (left) and M82 (right). M82 is one of two galaxies strongly influenced gravitationally by M81. The other, NGC 3077, is located off the top edge of this image.

Messier 81 is the largest galaxy in the M81 Group. The M81 Group is a group of 34 galaxies in the constellation Ursa Major.[8] This Group and the Local Group, containing the Milky Way,[8] are close together in the Virgo Supercluster.

Amateur astronomy[change | change source]

Messier 81 is about 10° northwest of Alpha Ursae Majoris.[1][9] Messier 81 and Messier 82 can both be easily seen using binoculars and small telescopes.[1]

Related pages[change | change source]

References[change | change source]

  1. 1.0 1.1 1.2 O'Meara, S. J. (1998). The Messier Objects. Cambridge University Press. ISBN 0-521-55332-6.
  2. 2.0 2.1 Jones, K. G. (1991). Messier's Nebulae and Star Clusters (2nd ed.). Cambridge University Press. ISBN 0-521-37079-5.
  3. Gordon, K. D.; Pérez-González, P. G.; Misselt, K. A.; Murphy, E. J.; Bendo, G. J.; Walter, F.; Thornley, M. D.; Kennicutt Jr., R. C. et al. (2004). "Spatially Resolved Ultraviolet, Hα, Infrared, and Radio Star Formation in M81". Astrophysical Journal Supplement Series 154 (1): 215–221. doi:10.1086/422714. 
  4. Pérez-González, P. G.; Kennicutt Jr., R. C.; Gordon, K. D.; Misselt, K. A.; Gil De Paz, A.; Engelbracht, C. W.; Rieke, G. H.; Bendo, G. J. et al. (2006). "Ultraviolet through Far-Infrared Spatially Resolved Analysis of the Recent Star Formation in M81 (NGC 3031)". Astrophysical Journal 648 (2): 987–1006. doi:10.1086/506196. 
  5. "NASA/IPAC Extragalactic Database". Results for extended name search on NGC 3031. Retrieved 2007-02-27.
  6. Ripero, J.; Garcia, F.; Rodriguez, D.; Pujol, P.; Filippenko, A. V.; Treffers, R. R.; Paik, Y.; Davis, M. et al. (1993). "Supernova 1993J in NGC 3031". IAU Circular 5731: 1. 
  7. Schmidt, B.P.; Kirshner, R.P.; Eastman, R.G.; Grashuis, R.; Dell'Antonio, I.; Caldwell, N.; Foltz, C.; Huchra, John P. et al. (1993). "The unusual supernova SN1993J in the galaxy M81". Nature 364 (6438): 600–602. doi:10.1038/364600a0. 
  8. 8.0 8.1 Karachentsev, I. D. (2005). "The Local Group and Other Neighboring Galaxy Groups". Astronomical Journal 129 (1): 178–188. doi:10.1086/426368. 
  9. Eicher, D. J. (1988). The Universe from Your Backyard. Cambridge University Press. ISBN 0-521-36299-7.

Other websites[change | change source]