M81 Group
The M81 Group is a group of galaxies, which is located in the immediate vicinity of the Local Group. For local group next to the Milky Way includes the Andromeda galaxy. The best known members of the M81 group are the two galaxies Messier 81 ( M81 ), from which is derived the name, and Messier 82 ( M82 ). Overall, belong to the 60 galaxies in this group, with seven large galaxies are lower.
Discovery history
The first members of the M81 group were already known in the late 18th century. The two best known of the group galaxies, M81 and M82, were discovered on December 31, 1774 by the German astronomer Johann Elert Bode. Regardless of both galaxies were found in August 1779 by Pierre Méchain, which made her record by Charles Messier in his catalog. All NGC objects in the M81 group have been spotted 1788-1801 by William Herschel and cataloged.
Morphology
The M81 group extends across the constellations Ursa Major and giraffe and has an angular extent of approximately 40 ° × 20 °, which corresponds to about 1.8 × 0.9 × 5.87 megaparsecs or 2.93 million light years.
The distance from our Sun to the center of the galaxy cluster is about 12 million light-years. This is the M81 group of our local group of galaxies located second closest. Nearby you will find parts of the Sculptor Group, a cluster of galaxies whose center is also about 12 million light- years away.
The M81 group and the local group belong to some other galaxy groups in the Virgo supercluster, forms the center of the Virgo cluster of galaxies. Due to the low redshift of the members of the M81 group is to assume that the M81 group moved as well as the local group on the center of the Virgo cluster of galaxies. The center of the M81 group form the galaxies M81, M82 and NGC 3077 as well as some other spiral galaxies and dwarf irregular galaxies.
The mass of the visible matter, including the calculated mass of the dark matter is ( 1.6 ± 0.3 ) · 1012 M ☉.
Galaxies in the M81 group
The table is compiled from the data of Atlas of the Universe and The M81 group of Galaxies: New distances, kinematics and structure ( 2002). The data for the type, coordinates, brightness, and the apparent diameters are taken from the NASA / IPAC Extragalactic Database. The data can be retrieved in the NED database with the names in the Name column ( exceptions: KK = KK98, HS = HS98, FM = FM2000 ). The distances derived from the works of Karachentsev 2005 and 2002.