Messier 81
· INTRODUCTION
Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away, with a diameter of 90,000 light years, about half the size of the Milky Way, within the constellation Great Bear. Due to its proximity to Earth, large size, and active galactic nucleus (which harbors a seventy million M supermassive black hole), Messier eighty one has been studied extensively by skilled astronomers. The galaxy's giant size and comparatively high brightness conjointly makes it a well-liked target for amateur astronomers.
Messier eighty one and Messier eighty two will each be viewed simply exploitation binoculars and little telescopes. the 2 objects square measure typically not noticeable to the unaided eye, though extremely old amateur astronomers is also ready to see Messier eighty one underneath exceptional observant conditions with a awfully dark sky.Telescopes with apertures of eight inches (20 cm) or larger square measure required to distinguish structures within the galaxy. Its way northern declination makes it typically visible for observers within the hemisphere. It is not visible to most observers within the hemisphere, except those in an exceedingly slim latitude vary in real time south of the equator.
Most of the emission at infrared wavelengths originates from interstellar dust. This interstellar dust is found primarily within the galaxy's spiral arms, and it has been shown to be associated with star formation regions. 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.
Only one star has been detected in Messier eighty one. The supernova, named SN 1993J, was discovered on 28 March 1993 by F. García in European nation. 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 looked a lot of sort of a kind II star (a star shaped by the explosion of a large star) with robust element spectral 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 supernova 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. The scientific results from this supernova suggested that type Ib and Ic supernovae were truly shaped through the explosions of big stars through processes kind of like those happening in sort II supernovae. The star was conjointly accustomed estimate a distance of 8.5 ± 1.3 Mly (2.6 ± 0.4 Mpc) to Messier 81. As a local galaxy, the Central Bureau for Astronomical Telegrams (CBAT) tracks novae in M81 along with M31 and M33.
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