Messier 81, also known as NGC 3031 or Bode's Galaxy, is a grand design unbarred spiral galaxy located approximately 11.8 million light years away from Earth in the constellation of Ursa Major.
Discovery[]
Messier 81 was first discovered by Johann Elert Bode on December 31, 1774. Due to this, it is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, and listed it in the Messier Catalogue.
Details[]
Messier 81 is located 11.8 million light years away from Earth. Because of its close proximity to Earth, its large size and active galactic nucleus, Messier 81 has been studied extensively by professional astronomers. The galaxy's large size and brightness also makes it a popular target for amateur astronomers.
Messier 81 is the largest and brightest galaxy in the M81 Group, which is a group of 34 galaxies located in Ursa Major. It contains Messier 81, Messier 82, and several other smaller galaxies.
The central bulge of this galaxy is significantly larger than the Milky Way's bulge. Its center contains a supermassive black hole of around 70 million solar masses. This black hole is about 15 times the mass of the Milky Way's center black hole.
Messier 81 may be undergoing a surge of star formation along the spiral arms due to a close encounter that it likely had with the nearby galaxies Messier 82 and NGC 3077 about 300 million years ago. The encounter has left traces in the spiral pattern of M81, first making it overall more pronounced, and second in the form of the dark linear feature in the lower left of the nuclear region. The galaxies are rather close together, as heir centers are separated by a distance of around 150,000 light years.
Supernova[]
One supernova has been detected in Messier 81. The supernova, named SN 1993J, was discovered on MArch 28, 1993, by F. García in Spain. At the time, it was the second brightest supernova observed in the 20th century. The spectral characteristics of the supernova changed over time. Initially it appeared to be a Type II supernova with strong hydrogen spectral line emission, but later, the hydrogen lines faded and strong helium spectral lines appeared, making the supernova look more like a type Ib.