Messier 81
Galaxy Messier 81 |
|
---|---|
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
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
- Hubble Space Telescope
- Spitzer space telescope
- M81 at SEDS
- M81 group at SEDS
- (M81 and M82)
- (M81 and M82)
- THINGS The HI Nearby Galaxy Survey
- H0 Key project over M81
- astronews: Impressive view of spiral galaxy M81 May 29, 2007
- astronews: Picture of the day February 15, 2013
- Spektrum.de : Collection of amateur recordings from Messier 81 , 82 & surroundings
Individual evidence
- ↑ a b c d e NASA / IPAC EXTRAGALACTIC DATABASE
- ↑ a b c d e SEDS : NGC 3031
- ↑ 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
- ↑ Michael Fritz: " The spiral galaxy Messier 81 in the constellation Great Bear " in " Stars and Space " April 2009 p. 78
- ↑ Astronews