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The M42 nebula is estimated to be 24 light-years across (so its apparent size from Earth is approximately 1 degree). It has a mass of about 2,000 times that of the Sun . Older texts frequently refer to the Orion Nebula as the Great Nebula in Orion or the Great Orion Nebula .
Given the scientific significance of M42, Orion's Sword is a popular spot for stellar and protostellar studies. Using the Hubble Space Telescope , O'dell et al. focused on identifying previously unseen features of the nebula, such as high-ionization shocks, compact sources, and protoplanetary disks . [ 6 ]
M42 Stahlhelm, a type of German WWII helmet; M42, a Smith & Wesson hammerless revolver; M42 United Defense submachine gun, an American weapon used in World War II; M42 command truck; In manufacturing: M42 is the Unified numbering system code ("miscellaneous nonferrous metals and alloys") for a grade of high-speed steel with cobalt
Charles Messier. The first edition of 1774 covered 45 objects (M1 to M45).The total list published by Messier in 1781 contained 103 objects, but the list was expanded through successive additions by other astronomers, motivated by notes in Messier's and Méchain's texts indicating that at least one of them knew of the additional objects.
Proplyds in the Orion Nebula. A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star.Nearly 180 proplyds have been discovered in the Orion Nebula. [1]
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outside the atmosphere of Earth. The field of astronomy features an extensive vocabulary and a ...
For planets and asteroids, a definition of absolute magnitude that is more meaningful for non-stellar objects is used. The absolute magnitude, commonly called H {\displaystyle H} , is defined as the apparent magnitude that the object would have if it were one astronomical unit (AU) from both the Sun and the observer, and in conditions of ideal ...
It was discovered on May 3, 1764, [10] and was the first Messier object to be discovered by Charles Messier himself. Messier originally mistook the object for a nebula without stars.