DATA :Misti Mountain Observatory


Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 millionlight-years away in the constellationUrsa Major. It has a D25 isophotal diameter of 29.44 kiloparsecs (96,000 light-years).=10.5px Because of its relative proximity to the Milky Way galaxy, large size, and active galactic nucleus (which harbors a 70 million M☉[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.=10.5px  In late February 2022, astronomers reported that M81 may be the source of FRB 20200120E, a repeating fast radio burst.Messier 81 was first discovered by Johann Elert Bode on 31 December 1774.=10.5px  Thus, it is sometimes referred to as "Bode's Galaxy". In 1779, Pierre Méchain and Charles Messier reidentified Bode's object, hence listed it in the Messier Catalogue.

The galaxy is to be found approximately 10° northwest of Alpha Ursae Majoris (Dubhe) along with several other galaxies in the Messier 81 Group.=10.5px Its apparent magnitude due to its distance means it requires a good night sky and only rises very briefly and extremely low at its southernmost limit from Earth's surface, about the 20th parallel south. Messier 81 and Messier 82 are considered ideal for viewing using binoculars and small telescopes.=10.5px 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.=10.5px Telescopes with apertures of 8 inches (20 cm) or larger are needed to distinguish structures in the galaxy. An infrared image of Messier 81 taken by the Spitzer Space Telescope.
The blue colors represent stellar emission observed at 3.6 μm.=10.5px  The green colors represent 8 μm emission originating primarily from polycyclic aromatic hydrocarbons in the interstellar medium.=10.5px  The red colors represent 24 μm emission originating from heated dust in the interstellar medium.

The galaxy is best observed during April. Most of the emission at infrared wavelengths originates from interstellar dust.=10.5px  This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation regions.=10.5px The general explanation is that the hot, short-lived blue stars that are found within star formation regions are very effective at heating the dust and thus enhancing the infrared dust emission from these regions. It is estimated M81 has 210 ± 30 globular clusters.=10.5px In late February 2022, astronomers reported that M81 may be the source of FRB 20200120E, a repeating fast radio burst. M81 (left) and M82 (right). M82 is one of two galaxies strongly influenced gravitationally by M81.

The other, NGC 3077, is located off the top edge of this image. M81 with satellite galaxy Holmberg IX in the top center-right corner Only one supernova has been detected in Messier 81.=10.5px  The supernova, named SN 1993J, was discovered on 28 March 1993 by F. García in Spain.=10.5px  At the time, it was the second brightest supernova observed in the 20th century,=10.5px  peaking at an apparent magnitude of 10.7. The spectral characteristics of the supernova changed over time. Initially, it looked more like a type II supernova (a supernova formed by the explosion of a supergiant star) with strong hydrogenspectral line emission, but later the hydrogen lines faded and strong helium spectral lines appeared, making the supernova look more like a type Ib. Moreover, the variations in SN 1993J's luminosity over time were not like the variations observed in other type II supernovae,=10.5px but did resemble the variations observed in type Ib supernovae.  Hence, the supernova has been classified as a type IIb, a transitory class between type II and type Ib.=10.5px The scientific results from this supernova suggested that type Ib and Ic supernovae were formed through the explosions of giant stars through processes similar to those taking place in type II supernovae.=10.5px  Despite the uncertainties in modeling the unusual supernova, it was also used to estimate a very approximate distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Messier 81.=10.5px As a local galaxy,

the Central Bureau for Astronomical Telegrams (CBAT) tracks novae in M81 along with M31 and M33. Messier 81 is the largest galaxy in the M81 Group, a group of 34 in the constellation Ursa Major=10.5px At approximately 11.7 Mly (3.6 Mpc) from the Earth, it makes this group and the Local Group, containing the Milky Way,=10.5px  relative neighbors in the Virgo Supercluster. Gravitational interactions of M81 with M82 and NGC 3077=10.5px  have stripped hydrogen gas away from all three galaxies, forming gaseous filamentary structures in the group.=10.5px  Moreover, these interactions have allowed interstellar gas to fall into the centers of M82 and NGC 3077, leading to vigorous star formation or starburst activity there.The distance to Messier 81 has been measured by Freedman et al =10.5px  to be 3.63 ± 0.34 Megaparsecs (11.8 ± 1.1 million light years) by using the Hubble Space Telescope to identify classical Cepheid variables and measure their periods using the period-luminosity relation discovered by Henrietta Swan Leavitt.