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Galaxy morphological classification is a system used by astronomers to divide galaxies into groups based on their visual appearance. There are several schemes in use by which galaxies can be classified according to their morphologies, the most famous being the Hubble sequence , devised by Edwin Hubble and later expanded by Gérard de ...
[21] [22] Although not really a shortcoming, since the 1961 Hubble Atlas of Galaxies, [23] the primary criteria used to assign the morphological type (a, b, c, etc.) has been the nature of the spiral arms, rather than the bulge-to-disk flux ratio, and thus a range of flux ratios exist for each morphological type, [23] [full citation needed] [24 ...
Hubble proved that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. [4] He used the strong direct relationship between a classical Cepheid variable 's luminosity and pulsation period [ 5 ] [ 6 ] (discovered in 1908 by Henrietta Swan Leavitt [ 7 ] ) for scaling ...
2014 – The Laniakea Supercluster, the galaxy supercluster that is home to the Milky Way is defined via a new way of defining superclusters according to the relative velocities of galaxies. [22] [23] The new definition of the local supercluster subsumes the prior defined local supercluster, the Virgo Supercluster, as an appendage. [24] [25 ...
NGC 1300, viewed nearly face-on; Hubble Space Telescope image. A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. [1] Bars are found in about two thirds of all spiral galaxies in the local universe, [2] and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well.
Explanations for how galaxies formed and evolved must be able to predict the observed properties and types of galaxies. Edwin Hubble created an early galaxy classification scheme, now known as the Hubble tuning-fork diagram. It partitioned galaxies into ellipticals, normal spirals, barred spirals (such as the Milky Way), and irregulars. These ...
The observational result of Hubble's law, the proportional relationship between distance and the speed with which a galaxy is moving away from us, usually referred to as redshift, is a product of the cosmic distance ladder. Edwin Hubble observed that fainter galaxies are more redshifted. Finding the value of the Hubble constant was the result ...
The giant elliptical galaxy ESO 325-4. An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main classes of galaxy described by Edwin Hubble in his Hubble sequence and 1936 work The Realm of the Nebulae, [1] along with spiral and lenticular galaxies.