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Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a grand design spiral galaxy about 12 million light-years away in the constellation Ursa Major. It has a D 25 isophotal diameter of 29.44 kiloparsecs (96,000 light-years ).
The M81 Group is a galaxy group in the constellations Ursa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses. [1] The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the Local Group. [1]
The x, y, z axes of frame S are oriented parallel to the respective primed axes of frame S′. The origins of frames S and S′ coincide at time t = 0 in frame S and also at t′ = 0 in frame S′. [2]: 107 Frame S′ moves in the x-direction of frame S with velocity v as measured in frame S.
The second Gaia celestial reference frame (Gaia–CRF2), based on 22 months of observations of over half a million extragalactic sources by the Gaia spacecraft, appeared in 2018 and has been described as "the first full-fledged optical realisation of the ICRS, that is to say, an optical reference frame built only on extragalactic sources."
M81 is a nearly face-on spiral galaxy 11.8 million light-years from Earth. Like most spiral galaxies, it has a core made up of old stars, with arms filled with young stars and nebulae. Along with M82, it is a part of the galaxy cluster closest to the Local Group. M82 is a nearly edgewise galaxy that is interacting gravitationally with M81.
(The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.) Substituting D = cH −1 into the equation for Hubble's law, v = H 0 D reveals that the Hubble distance specifies the distance from our location to those galaxies which are currently receding from us at the speed of light
The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [3] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or ...
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.It is the second-largest member of the M81 Group, with the D 25 isophotal diameter of 12.52 kiloparsecs (40,800 light-years).