The M81 Group is a
galaxy group
A galaxy group or group of galaxies (GrG) is an aggregation of galaxies comprising about 50 or fewer gravitationally bound members, each at least as luminous as the Milky Way (about 1010 times the luminosity of the Sun); collections of galaxie ...
in the
constellations
Ursa Major
Ursa Major (; also known as the Great Bear) is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater (or larger) bear," referring to and contrasting it with nearby Ursa ...
and
Camelopardalis that includes the galaxies
Messier 81
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of . Because of its relative proximity to the Milky Way ...
and
Messier 82
Messier 82 (also known as NGC 3034, Cigar Galaxy or M82) is a starburst galaxy approximately 12 million light-years away in the constellation Ursa Major. It is the second-largest member of the M81 Group, with the D25 isophotal diameter of . It ...
, as well as several other galaxies with high apparent brightnesses.
The approximate center of the group is located at a distance of 3.6
Mpc, making it one of the nearest groups to the
Local Group
The Local Group is the galaxy group that includes the Milky Way.
It has a total diameter of roughly , and a total mass of the order of .
It consists of two collections of galaxies in a "dumbbell" shape: the Milky Way and its satellites form ...
.
The group is estimated to have a total mass of (1.03 ± 0.17).
The M81 Group, the Local Group, and other nearby groups all lie within the
Virgo Supercluster
The Virgo Supercluster (Virgo SC) or the Local Supercluster (LSC or LS) is a mass concentration of galaxies containing the Virgo Cluster and Local Group, which itself contains the Milky Way and Andromeda galaxies, as well as others. At least ...
(i.e. the Local Supercluster).
Members
The table below lists galaxies that have been identified as associated with the M81 Group by I. D. Karachentsev.
Note that the object names used in the above table differ from the names used by Karachentsev.
NGC,
IC,
UGC, and
PGC numbers have been used in many cases to allow for easier referencing.
Interactions within the group
Messier 81, Messier 82, and NGC 3077 are all strongly
interacting
Interaction is action that occurs between two or more objects, with broad use in philosophy and the sciences. It may refer to:
Science
* Interaction hypothesis, a theory of second language acquisition
* Interaction (statistics)
* Interactions o ...
with each other.
Observations of the 21-centimeter
hydrogen line
The hydrogen line, 21 centimeter line, or H I line is the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation has a precise frequency of , w ...
indicate how the galaxies are connected.
The gravitational interactions have stripped some
hydrogen
Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...
gas away from all three galaxies, leading to the formation of filamentary gas structures within the group.
Bridges of neutral hydrogen have been shown to connect M81 with M82 and NGC 3077.
Moreover, the interactions have also caused some
interstellar gas
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
to fall into the centers of Messier 82 and NGC 3077, which has led to strong
starburst activity (or the formation of many stars) within the centers of these two galaxies.
Computer simulations of
tidal interactions
The tidal force is a gravitational effect that stretches a body along the line towards the center of mass of another body due to a gradient (difference in strength) in gravitational field from the other body; it is responsible for diverse phenomen ...
have been used to show how the current structure of the group could have been created.
Gallery
The mysteries of UGC 8201.jpg, Galaxy UGC 8201 is a dwarf irregular galaxy member of the M81 galaxy group.
M81+M82-and other galaxies.jpg, Amateur picture Messier 81
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D25 isophotal diameter of . Because of its relative proximity to the Milky Way ...
+ 82 and NGC 3077 all of the M81 group, 33 frames stacked of 1 minute each.
Image:M81m82 galex f.jpg, The spiral galaxies Messier 81 and 82 and the dwarf galaxy Holmberg IX from GALEX
Image:M81 wide Galex.jpg, Close up view of Messier 81 from GALEX
Image:Messier81 highres.jpg, The spiral galaxy Messier 81 from Spitzer Space Telescope
Image:Ssc2003-06c.jpg, The spiral galaxy Messier 81 from Spitzer Space Telescope
Image:M82 HST ACS 2006-14-a-large web.jpg, Starburst galaxy Messier 82 from Hubble Space Telescope
Image:NGC2403 3.6 5.8 8.0 microns spitzer.png, NGC 2403 in mid-infrared view, combining the 3.6, 5.8 and 8.0 µm bands of the Spitzer Space Telescope
Image:NGC2403 3.6 8.0 24 microns spitzer.png, NGC 2403 in Mid-infrared view, combining the 3.6, 8.0 and 24 µm bands of the Spitzer Space Telescope
Image:NGC 2403HST.jpg, NGC 2403 from Hubble Space Telescope
Image:NGC 2403HSTSN.jpg, NGC 2403 from Hubble Space Telescope illustrated
Image:Galaxy-NGC-2403-with-SN2004DJ.jpeg, Supernova SN2004DJ in the spiral galaxy NGC 2403
Image:NGC2403-SN2004dj.jpg, Supernova 2004dj in NGC 2403
Image:NGC 4236 I FUV g2006.jpg, NGC 4236 from GALEX
Image:NGC 2366HST.jpg, NGC 2366 from Hubble Space Telescope
Image:NGC 2976SSTFull.jpg, Galaxy NGC 2976 from Spitzer Space Telescope in infrared
Image:NGC2976.jpg, Galaxy NGC 2976 from an amateur Astronomer
Image:NGC 4605 GALEX WikiSky.jpg, Galaxy NGC 4605 from GALEX
Image:Ngc2363HST.jpg, NGC 2363 from Hubble Space Telescope
Image:NGC 2537 I FUV g2006.jpeg, NGC 2537 from GALEX
Image:Holmberg IISST.jpg, Holmberg II from Spitzer Space Telescope in infrared
Image:M81DwarBSST.jpg, UGC 5423 / M81 dwarf B from Spitzer Space Telescope in infrared
Image:NGC 3077 2MASS.jpg, NGC 3077 from 2MASS
Image:IC 2574 Hubble WikiSky.jpg, IC 2574
See also
*
UGC 5497
References
External links
M81 Group @ SEDS{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System
Virgo Supercluster
Galaxy clusters