Messier 81

from Wikipedia, the free encyclopedia
Galaxy
Messier 81
{{{Card text}}}
Messier 81 HST.jpg
Photo from the Hubble Space Telescope
AladinLite
Constellation Big Bear
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 09 h 55 m 33.2 s
declination + 69 ° 03 ′ 55 ″
Appearance
Morphological type SA (s) from;
LINER Sy1.8  
Brightness  (visual) 7.0 likes
Brightness  (B-band) 7.8 likes
Angular expansion 24.9 ′ × 11.5 ′
Position angle 157 °
Surface brightness 13.0 mag / arcmin²
Physical data
Affiliation M81 group ,
Virgo supercluster , LGG 176  
Redshift −0.000113 ± 0.000013  
Radial velocity −34 ± 4 km / s  
Stroke distance
v rad  / H 0 		(12 ± 2)  ·  10 6  ly
(3.66 ± 0.47)  Mpc 
diameter 95,000 ly
history
discovery Johann Elert Bode
Discovery date December 31, 1774
Catalog names
M  81 • NGC  3031 • UGC  5318 • PGC  28630 • CGCG  333-007 • MCG  + 12-10-010 • IRAS  09514 + 6918 • GC  1953 and 1949 • h  649 • KCPG 218A • Bode 17 • Koehler 8A

Messier 81 , also known as NGC 3031 or Bodes Galaxy , is a 7.0 mag bright spiral galaxy of the Hubble type Sb in the constellation Great Bear in the northern sky . The apparent area of ​​M81 is 25 ′ by 12 ′ less than the full moon (apparent diameter around 30 ′). Compared to the Andromeda Nebula (M31), M81 appears noticeably smaller at about one-thirtieth of its area and is about four times further away, about 12 million light years .

The distance was determined as part of the HST Key Project to precisely determine the Hubble constant to be 12 ± 1 million light years. Messier 81 is 82,000 light years across and an estimated 200 billion stars, slightly smaller than our Milky Way . The central black hole has a mass of around 70 million solar masses, which is around 15 times more massive than the black hole in the center of our galaxy.

observation

Photograph with the inscription of some striking celestial objects in the vicinity of the galaxies M 81 and M 82 . On the left and below the constellation Great Bear with the stars Merak and Dubhe can be seen. At the top right is the dragon constellation with the star Giausar in the tip of the dragon's tail.

From Earth we see the galaxy at an angle, which has relatively loose spiral arms, but has many stars near the center. The structure of the galaxy is easier to see in the UV and IR spectral range.

  • UV absorption by GALEX , in the wavelength range 135–175 nm

  • IR image by SST , at 3.6 µm (blue), 8 µm (green) and 24 µm (red)

  • Taken in the far infrared by the Herschel space telescope

  • Amateur shot of the M81 and M82

With a brightness of 7.0 mag, M81 is already clearly visible in binoculars . Nearby is the somewhat weaker spiral galaxy M82 , which is also noticeable due to its greater surface brightness . These two galaxies form the core of the M81 galaxy group , which as a real physical group is one of the closest neighbors to our Local Group . This group includes NGC 2403 , NGC 3077 and NGC 2976 , among others . Messier 81 also has a small satellite galaxy, the irregular star system UGC 5336 (Holmberg IX).

The object is sometimes also called Bode's galaxy in honor of its discoverer , as it was discovered by Johann Elert Bode on December 31, 1774 .

literature

  • Wolfgang Steinicke: A nightmare for the Herschel family. Stars and Space 46 (2), pp. 61-65 (2007), ISSN  0039-1263 ; Discovery of the galaxies M81 and M82

Web links

Commons : Messier 81  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e NASA / IPAC EXTRAGALACTIC DATABASE
  2. ↑ a b c d e SEDS : NGC 3031
  3. ↑ Freedman, Wendy L .; Hughes, Shaun M .; Madore, Barry F .; Mold, Jeremy R .; Lee, Myung Gyoon; Stetson, Peter; Kennicutt, Robert C .; Turner, Anne; Ferrarese, Laura; Ford, Holland; Graham, John A .; Hill, Robert; Hoessel, John G .; Huchra, John; Illingworth, Garth D .: The Hubble Space Telescope Extragalactic Distance Scale Key Project. I. The Discovery of Cepheids and a New Distance to M81 in Astrophysical Journal vol. 427, p. 628, June 1994, accessed Jan. 5, 2020
  4. ↑ Michael Fritz: " The spiral galaxy Messier 81 in the constellation Great Bear " in " Stars and Space " April 2009 p. 78
  5. ↑ Astronews