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.

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.
References in periodicals archive ?
The Small Magellanic Cloud has formed in part through its interactions with the Milky Way and with what ANU calls its "companion," a larger dwarf galaxy called the Large Magellanic Cloud.
It only has 10% of the mass of the Milky Way, and so the fastest runaways born in this dwarf galaxy can easily escape its gravity.
The dwarf galaxy was said to lie in the direction of the constellation Virgo, 30,000 light years from Earth.
The new dwarf galaxy found by Holyhead-born Dr Jones and his team has ``merely'' tens of millions of stars.
Space expert Brian Yanny said at a meeting of the American Astronomical Society in Seattle: "The stars may be what's left of a collision between our Milky Way and a smaller, dwarf galaxy that occurred billions of years ago.
The new galaxy is of a type known as a dwarf galaxy because it is faint and small - unlike the Milky Way and Andromeda galaxies, the two local giants.
A team of astronomers from Kapteyn Astronomical Institute and Leiden Observatory, both in the Netherlands, used the data to measure the 3D movement of stars in the nearby Sculptor Dwarf Galaxy (SDG), a satellite galaxy to our own, located about 300,000 light-years from Earth.
In this Letter, we presented a new faint dwarf galaxy, d1005+68, with properties consistent with being a satellite of the M81 Group.
Possible explanations for how the stars got so far away have included that they were ejected from the Milky Way's disk, that they are the brightest members of a nearly invisible dwarf galaxy, or that they are the remnants of a galaxy shredded by the Milky Way's gravity.
This dwarf galaxy doesn't have many stars, but it is rich in dark matter, the invisible but predominant source of mass in the universe.
It is inside one of the densest galaxies known to date -- the M60-UCD1 dwarf galaxy that crams 140 million stars within a diameter of about 300 light-years, which is only 1/500th of our galaxy s diameter.
If confirmed by further observations, a halo of dark matter could mean that the Smith Cloud is actually a failed dwarf galaxy, an object that has all the right stuff to form a true galaxy, just not enough to produce stars.