Messier 81

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Messier 81

M81
Observation data: J2000 epoch
Constellation: Ursa Major
Right ascension: 09h 55m 33.2s[1]
Declination: +69° 3′ 55″[1]
Redshift: -34 ± 4 km/s[1]
Distance: 11.8 ± 1.1 Mly (3.6 ± 0.3 Mpc)[2]
Type: SA(s)ab[1]
Apparent dimensions (V): 26′.9 × 14′.1[1]
Apparent magnitude (V): 6.9[3]
Notable features:
Other designations
NGC 3031,[1] UGC 5318,[1] PGC 28630,[1]
Bode's Galaxy[4]
See also: Galaxy, List of galaxies


Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away in the constellation Ursa Major. M81 is one of the most striking examples of a grand design spiral galaxy, with near perfect arms spiraling into the very center.

M81 has an apparent magnitude of 6.9, making it one of the brightest galaxies that can be seen from the Earth. While compact objects of such magnitudes are visible to the naked eye under ideal conditions [1], the diffuse nature of M81 renders it too faint to see unaided, and thus cannot claim the title for furthest naked-eye object (which is usually taken to be M33)

Multiwavelength infrared observations of M81 by the Spitzer Space Telescope. The blue colors trace starlight in the 3.6 micrometre wave band. The green colors trace polycyclic aromatic hydrocarbon emission in the 8.0 micrometre wave band. The red colors trace hot dust emission in the 24 micrometre wave band.
Multiwavelength infrared observations of M81 by the Spitzer Space Telescope. The blue colors trace starlight in the 3.6 micrometre wave band. The green colors trace polycyclic aromatic hydrocarbon emission in the 8.0 micrometre wave band. The red colors trace hot dust emission in the 24 micrometre wave band.

Contents

[edit] History

[edit] Discovery

Messier 81 was first discovered by Johann Elert Bode in 1774[5]. Consequently, the galaxy is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, which was subsequently listed in the Messier Catalogue[5].

[edit] Supernovae

Only one supernova has been detected in Messier 81[6]. The supernova, named SN 1993J, was discovered on 28 March 1993 by F. Garcia in Spain[7]. At the time, it was the second brightest supernova observed in the twentieth century[8]. The spectral characteristics of the supernova changed over time. Initially, it looked more like a type II supernova (a supernovae formed by the explosion of a giant star) with strong hydrogen spectral line emission, but later the hydrogen lines faded and strong helium spectral lines appeared, making the supernova look more like a type Ib[8][9]. Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernovae[10][11] but did resemble the variations observed in type Ib supernovae[12]. Hence, the supernova has been classified as a "type IIb", a transitory class between type II and type Ib[9]. The scientific results from this supernova suggested that type Ib and Ic supernovae were actually formed through the explosions of giant stars through processes similar to what takes place in type II supernovae[9][13]. The supernova was also used to estimate a distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Messier 81[8].

[edit] Nearby galaxies and galaxy group information

Messier 81 is the largest galaxy in the M81 Group, a group of 34 galaxies located in the constellation Ursa Major[14]. The distance from the Earth to the group is approximately 11.7 Mly (3.6 Mpc), making this one of the closest groups to the Local Group, which contains the Milky Way[14].

M81 is gravitationally interacting with Messier 82 and NGC 3077[15]. The interactions have stripped some hydrogen gas away from all three galaxies, leading to the formation of filamentary gas structures in the group[15]. Moreover, the interactions have also caused some interstellar gas to fall into the centers of Messier 82 and NGC 3077, which has lead to strong starburst activity (or the formation of many stars) within the centers of these two galaxies[15].

[edit] M81 in fiction

In the fictional Star Fleet Universe, M81 is the home galaxy for a number of star-faring races, including the Tholians and Seltorians (who arrive in the Alpha Octant of the Milky Way in the SFU timeline) and the Bolosco (who establish themselves in the adjacent Omega Octant)[citation needed].

[edit] External links

[edit] References

  1. ^ a b c d e f g h NASA/IPAC Extragalactic Database. Results for NGC 3031. Retrieved on 2006-11-10.
  2. ^ I. D. Karachentsev, O. G. Kashibadze (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3-18. 
  3. ^ G. de Vaucouleurs, A. de Vaucouleurs, H. G. Corwin, R. J. Buta, G. Paturel, P. Fouque (1991). Third Reference Catalogue of Bright Galaxies. New York: Springer-Verlag. 
  4. ^ SIMBAD Astronomical Database. Results for NGC 3031. Retrieved on 2006-11-10.
  5. ^ a b K. G. Jones (1991). Messier's Nebulae and Star Clusters, 2nd edition, Cambridge: Cambridge University Press. ISBN 0-521-37079-5. 
  6. ^ NASA/IPAC Extragalactic Database. Results for extended name search on NGC 3031. Retrieved on 2007-02-27.
  7. ^ J. Ripero, F. Garcia, D. Rodriguez, P. Pujol, A. V. Filippenko, R. R. Treffers, Y. Paik, M. Davis, D. Schlegel, F. D. A. Hartwick, D. D. Balam, D. Zurek, R. M. Robb, P. Garnavich, B. A. Hong (1993). "Supernova 1993J in NGC 3031". IAU Circular 5731. 
  8. ^ a b c B. P. Schmidt, R. P. Kirshner, R. G. Eastman, R. Grashuis, I. dell'Antonio, N. Caldwell, C. Foltz, J. P. Huchra, A. A. E. Milone (1993). "The unusual supernova SN1993J in the galaxy M81". Nature 364: 600-602. 
  9. ^ a b c A. V. Filippenko, T. Matheson, L. C. Ho (1993). "The "Type IIb" Supernova 1993J in M81: A Close Relative of Type Ib Supernovae". Astrophysical Journal Letters 415: L103-L106. 
  10. ^ P. J. Benson, W. Herbst, J. J> Salzer, G. Vinton, G. J. Hanson, S. J. Ratcliff, P. F. Winkler, D. M. Elmegreen, F. Chromey, C. Strom, T. J. Balonek, B. G. Elmegreen (1994). "Light curves of SN 1993J from the Keck Northeast Astronomy Consortium". Astronomical Journal 107: 1453-1460. 
  11. ^ J. C. Wheeler, E. Barker, R. Benjamin, J. Boisseau, A. Clocchiatti, G. de Vaucouleurs, N. Gaffney, R. P. Harkness, A. M. Khokhlov, D. F. Lester, B. J> Smith, V. V. Smith, J. Tomkin (1993). "Early Observations of SN 1993J in M81 at McDonald Observatory". Astrophysical Journal 417: L71-L74. 
  12. ^ M. W. Richmond, R. R. Treffers, A. V. Filippenko, Y. Palik, B. Leibundgut, E. Schulman, C. V. Cox (1994). "UBVRI photometry of SN 1993J in M81: The first 120 days". Astronomical Journal 107: 1022-1040. 
  13. ^ A. V. Filippenko, T. Matheson, A. J. Barth (1994). "The peculiar type II supernova 1993J in M81: Transition to the nebular phase". Astronomical Journal 108: 2220-2225. 
  14. ^ a b I. D. Karachentsev (2005). "The Local Group and Other Neighboring Galaxy Groups". Astronomical Journal 129: 178-188. 
  15. ^ a b c M. S. Yun, P. T. P. Ho, K. Y. Lo (1994). "A high-resolution image of atomic hydrogen in the M81 group of galaxies". Nature 372: 530-532. 
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