dwarf galaxy


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Related to dwarf galaxy: Andromeda, Andromeda galaxy

dwarf galaxy

A galaxy that is unusually faint either because of its very small size, its very low surface brightness, or both. Since galaxies exist in a continuous range of sizes from the giant ellipticals downward, the dividing line between average and dwarf is somewhat arbitrary. Since no spiral or S0 galaxies have been observed with total magnitudes below –16, this is often used as a convenient demarcation line. They contain only a few million stars and are very difficult to observe against foreground stars because they are almost completely transparent. Dwarf galaxies may make up the bulk of the cosmic population and occur in all morphologies except as spiral galaxies.

The dwarf irregulars (dI) are the most numerous of these galaxies, and contain a significant fraction of their mass as neutral hydrogen gas in a dark halo (see also LSB galaxies). Dwarf ellipticals (dE) are dominated by metal-poor halo stars, and their lack of gas or dust suggests that any star formation occurred a long time ago in these systems. In contrast, the gas-rich blue compact dwarf (BCD) galaxies are undergoing active star formation with sizes and spectra resembling giant H II regions. See also extragalactic H II region.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

dwarf galaxy

[′dwȯrf ′gal·ik·sē]
(astronomy)
An elliptical galaxy with low mass and low luminosity, having at most a few tens of millions of stars.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Using the NASA/ESA Hubble Space Telescope, scientists have discovered a new dwarf galaxy relatively near the Milky Way.
"In this Letter, we presented a new faint dwarf galaxy, d1005+68, with properties consistent with being a satellite of the M81 Group.
The Milky Way's gravity has pulled their stars into long arcs that are much thinner than a pulled-apart dwarf galaxy. It's easier to calculate the path of stars streaming from a single compact object: Since the stars are all coming from a smaller point of origin, they're more or less on the same orbit.
The impact between the dwarf galaxy and the spiral galaxy caused a shock wave-akin to a sonic boom on Earth-that generated hot gas with a temperature of about 6 million degrees.
"This is a telltale sign that the dwarf galaxy came in on a really eccentric orbit and its fate was sealed," Vasily Belokurov, one of the authors of the work, said in a (https://www.eurekalert.org/pub_releases/2018-07/sf-tgs070318.php) statement.
Now a Russian-American team has added to the canon, finding the dwarf galaxy.
The team has just reported what appears to be another faint dwarf galaxy, about 100,000 light-years from Earth, in the constellation Ursa Major (http://xxx.lanl.gov/abs/ctstlv-ph/0606633).
University of Utah astronomer and his colleagues discovered that an ultracompact dwarf galaxy harbors a supermassive black hole -- the smallest galaxy known to contain such a massive light-sucking object.
Farrell speculates; a dwarf galaxy that was swallowed by the larger galaxy ESO 243-49, just as our own Milky Way Galaxy has swallowed dwarf galaxies.
Astronomers have found evidence that our home galaxy is tearing apart and swallowing a nearby collection of stars--most likely the remains of a dwarf galaxy. The galactic violence would be the latest confirmed act of cannibalism by the Milky Way (SN: 4/22/00, p.
"With the combination of Hubble and Green Bank Telescope observations, we can measure the composition and velocity of the gas to determine which dwarf galaxy is the culprit."
The stars might be the remains of an ancient run-in with a dwarf galaxy.