Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy located 12 million light-years away from earth (that's 12 Million TIMES 5.878 Trillion miles), with a diameter of 90,000 light years (10% smaller than the Milky Way), in the constellation Ursa Major.  M82 is half the size of M81 with a diameter of 47,000 light years.   Wrap your head around those numbers for a minute.  The objects in this photo are how far away?  Size matters.

Messier 81 is the largest galaxy in the M81 Group, a group of 34 galaxies in the constellation Ursa Major.  At approximately 11.7 Mly from our solar system, it makes this group and the Local Group, containing the Milky Way, relative neighbors in the Virgo Supercluster.  Due to its proximity to our galaxy, large size, and active galactic nucleus (which harbors a supermassive black hole), Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and relatively high brightness also makes it a popular target for amateur astronomers like myself.  

Messier 81 and Messier 82 (Cigar Galaxy) are considered ideal for viewing using binoculars (7x50) or small telescopes. The two objects are generally not observable to the unaided eye, although highly experienced amateur astronomers may be able to see Messier 81 under exceptional observing conditions with a very dark sky. Telescopes with apertures of 8 inches (20 cm) or larger are needed to distinguish structures in the galaxy.

Gravitational interactions of M81 with M82 have stripped hydrogen gas away from the galaxies, forming gaseous filamentary structures in the group. Moreover, these interactions have allowed interstellar gas to fall into the center of M82, leading to vigorous star formation or starburst activity there.

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. A member of the M81 Group, it is about five times more luminous than the Milky Way and has a center one hundred times more luminous. The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As the closest starburst galaxy to Earth, M82 is the prototypical example of this galaxy type.

Stars in M82's disk seem to have been formed in a burst 500 million years ago, leaving its disk littered with hundreds of clusters with properties similar to globular clusters (but younger), and stopped 100 million years ago with no star formation taking place in this galaxy outside the central starburst and, at low levels since 1 billion years ago, on its halo. A suggestion to explain those features is that M82 was previously a low surface brightness galaxy where star formation was triggered due to interactions with its giant neighbor.  Tidal forces caused by gravity have deformed M82, a process that started about 100 million years ago. This interaction has caused star formation to increase tenfold compared to "normal" galaxies.  M82 has undergone at least one tidal encounter with M81 resulting in a large amount of gas being funneled into the galaxy's core over the last 200 Million years. 

M81 & M82 are visible the whole year round in the Northern Hemisphere. The further north you are, the better the chances of seeing it. Any further south than Miami, you will not be able to it all year round. M81 is moving towards our solar system at 42 km/sec, rather slowly in space time.

Ignoring any difference in their respective distances from the Earth, the centers of M81 and M82 are visually separated by about 130,000 light-years, or approximately the distance across our Milky Way galaxy.