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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]
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).
It had been conjectured that the fixed stars were much farther away than the planets. Moon: Moon of a planet 3rd century BC 20 Earth radii (very inaccurate, true=64 Earth radii) Aristarchus of Samos made a measurement of the distance between the Earth and the Moon. The diameter of the Earth had been calculated previously.
(The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.) The Hubble distance would be the distance between the Earth and the galaxies which are currently receding from us at the speed of light, as can be seen by substituting D = cH −1 into the equation for Hubble's law, v = H 0 D.
Dark sky image with some objects around Pinwheel Galaxy (M 101). The quarter in the lower right shows the tail of Ursa Major with the stars Mizar, Alcor and Alkaid.. The Pinwheel Galaxy (also known as Messier 101, M101 or NGC 5457) is a face-on, unbarred, and counterclockwise spiral galaxy located 21 million light-years (6.4 megaparsecs) [5] from Earth in the constellation Ursa Major.
A fuller explanation of the concept of coordinate time arises from its relations with proper time and with clock synchronization. Synchronization, along with the related concept of simultaneity, has to receive careful definition in the framework of general relativity theory, because many of the assumptions inherent in classical mechanics and classical accounts of space and time had to be removed.
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 ...