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An Irr-II galaxy ( Irr II) is an irregular galaxy that does not appear to feature any structure that can place it into the Hubble sequence. A dI-galaxy (or dIrr) is a dwarf irregular galaxy. [7] This type of galaxy is now thought to be important to understand the overall evolution of galaxies, as they tend to have a low level of metallicity and ...
Galactic astronomy is the study of the Milky Way galaxy and all its contents. This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies. Galactic astronomy should not be confused with galaxy formation and evolution, which is the general study of galaxies, their formation ...
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 ...
Elliptical and lenticular galaxies are commonly referred to together as "early-type" galaxies, while spirals and irregular galaxies are referred to as "late types". This nomenclature is the source of the common, [18] but erroneous, belief that the Hubble sequence was intended to reflect a supposed evolutionary sequence, from elliptical galaxies ...
In astronomy, the Tully–Fisher relation ( TFR) is a widely verified empirical relationship between the mass or intrinsic luminosity of a spiral galaxy and its asymptotic rotation velocity or emission line width. Since the observed brightness of a galaxy is distance-dependent, the relationship can be used to estimate distances to galaxies from ...
Betelgeuse is an intrinsically variable star. A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either: [1] Intrinsic variables, whose luminosity ...
In irregular galaxies, open clusters may be found throughout the galaxy, although their concentration is highest where the gas density is highest. Open clusters are not seen in elliptical galaxies: Star formation ceased many millions of years ago in ellipticals, and so the open clusters which were originally present have long since dispersed.
Hubble Deep Field. Coordinates: 12 h 36 m 49.4 s, +62° 12′ 58″. The Hubble Deep Field. The Hubble Deep Field ( HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky ...