All Topics  
Dwarf galaxy

 

 
   Email Print
   Bookmark   Link
 

 

Dwarf galaxy
 
 
  Topics Dwarf galaxy Topic Home

A dwarf galaxy is a small galaxy
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
 composed of up to several billion star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
s, a small number compared to our own Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
's 200-400 billion stars. The Large Magellanic Cloud
Large Magellanic Cloud

The Large Magellanic Cloud is a nearby galaxy, one thought to be a satellite galaxy of our own. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center of the Milky Way....
, containing over 30 billion stars, is sometimes classified as a dwarf galaxy while others consider it a full-fledged galaxy going around the Milky Way galaxy.

ent theory believes most galaxies, including dwarf galaxies, form in association with dark matter
Dark matter

In astronomy and physical cosmology, dark matter is Hypothesis matter that is undetectable by its emitted electromagnetic radiation, but whose presence can be inferred from gravity effects on visible matter....
 or out of gas containing metals.






Discussion
Ask a question about 'Dwarf galaxy'
Start a new discussion about 'Dwarf galaxy'
Answer questions from other users
Full Discussion Forum



Encyclopedia


A dwarf galaxy is a small galaxy
Galaxy

A galaxy is a massive, gravitation system that consists of stars and stellar remnants, an interstellar medium of gas and cosmic dust, and an important but poorly-understood component tentatively dubbed dark matter....
 composed of up to several billion star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
s, a small number compared to our own Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
's 200-400 billion stars. The Large Magellanic Cloud
Large Magellanic Cloud

The Large Magellanic Cloud is a nearby galaxy, one thought to be a satellite galaxy of our own. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center of the Milky Way....
, containing over 30 billion stars, is sometimes classified as a dwarf galaxy while others consider it a full-fledged galaxy going around the Milky Way galaxy.

Creation of dwarf galaxies

Current theory believes most galaxies, including dwarf galaxies, form in association with dark matter
Dark matter

In astronomy and physical cosmology, dark matter is Hypothesis matter that is undetectable by its emitted electromagnetic radiation, but whose presence can be inferred from gravity effects on visible matter....
 or out of gas containing metals. However, NASA's Galaxy Evolution Explorer space probe identified new dwarf galaxies forming out of gases lacking metals. These galaxies were located in the Leo Ring, a cloud of hydrogen and helium around two massive galaxies in the constellation Leo
LEO

LEO as an acronym may refer to:* Low Earth orbit* Police officer* Louisville Eccentric Observer, an alternative urban newspaper in Louisville, Kentucky...
.

Local dwarfs

There are many dwarf galaxies in the Local Group
Local Group

The Local Group is the galaxy groups and clusters of galaxy that includes our galaxy, the Milky Way. The group comprises over 50 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy....
: these small galaxies frequently orbit around larger galaxies, such as the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
, the Andromeda Galaxy
Andromeda Galaxy

The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda . It is the nearest spiral galaxy to our own, the Milky Way Galaxy....
 and the Triangulum Galaxy
Triangulum Galaxy

The Triangulum Galaxy is a spiral galaxy approximately 3 million light-years away in the constellation Triangulum. The galaxy is also sometimes informally referred to as the Pinwheel Galaxy by some amateur astronomy references...
. A recent paper has suggested that many dwarf galaxies were created by tidal forces during the early evolution of the Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
 and Andromeda
Andromeda Galaxy

The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years away in the constellation Andromeda . It is the nearest spiral galaxy to our own, the Milky Way Galaxy....
. Tidal dwarf galaxies are produced when galaxies collide and their gravitational masses interact. Streams of galactic material are pulled out away from the parent galaxies and the halos of dark matter that surround them.

The Milky Way has 14 known dwarf galaxies orbiting it, and recent discoveries have also led astronomers to believe the largest globular cluster
Globular cluster

A globular cluster is a sphere collection of stars that orbits a Galactic Center as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and relatively high stellar densities toward their centers....
 in the Milky Way, Omega Centauri
Omega Centauri

Omega Centauri or NGC 5139 is a globular cluster seen in the constellation of Centaurus, discovered by Edmond Halley in 1677 who listed it as a Nebula....
, is in fact the core of a dwarf galaxy with a black hole in its center, which was at some time absorbed by the Milky Way. (See Milky Way
Milky Way

The Milky Way, sometimes called simply the Galaxy, is the galaxy in which the Solar System is located. It is a barred spiral galaxy that is part of the Local Group of galaxies....
 for more information.)

Dwarf galaxies

Dwarf galaxies come in many different morphologies:
  • Elliptical galaxy
    Elliptical galaxy

    An elliptical galaxy is a galaxy having an approximately ellipsoid shape and a smooth, nearly featureless brightness profile. They range in shape from nearly spherical to highly flattened and in size from hundreds of millions to over one trillion stars....
    : dwarf elliptical galaxy
    Dwarf elliptical galaxy

    Dwarf elliptical galaxies, or dE's, are elliptical galaxy that are much smaller than others. They are classified as dE, and are quite common in galaxy groups and clusters, and are usually companions to other galaxies....
     (dE) and its subtype dwarf spheroidal galaxy
    Dwarf spheroidal galaxy

    Dwarf spheroidal galaxy is a technical term in astronomy applied to low luminosity galaxies that are companions to the Milky Way and to the similar systems that are companions to the Andromeda Galaxy....
     (dSph)
  • Irregular galaxy
    Irregular galaxy

    Some galaxies do not have a regular shape, like a spiral galaxy or an elliptical galaxy. Those galaxies are known as irregular galaxies. Their shape is uncommon....
    : dwarf irregular galaxy (dI)
  • Spiral galaxy
    Spiral galaxy

    A spiral galaxy is a galaxy belonging to one of the three main galaxy morphological classification originally described by Edwin Hubble in his 1936 work ?The Realm of the Nebulae? and, as such, forms part of the Hubble sequence....
    : dwarf spiral galaxy


Hobbit galaxies

The recently coined term, hobbit galaxy has been used to describe galaxies smaller and dimmer than dwarf galaxies.

Ultra Compact Dwarfs

Ultra Compact Dwarf galaxies (UCD) are a recently discovered class of very compact galaxies with very high stellar population counts. They are thought to be on the order of 200 light years across, with a hundred million stars. It is theorized that these are the cores of nucleated dwarf elliptical galaxies, that have been stripped of gas and outlying stars by tidal interactions, travelling through the hearts of rich clusters. UCDs have been found in the Virgo Cluster
Virgo Cluster

The Virgo Cluster is a galaxy cluster at a distance of approximately 1 E22 m light year away in the constellation Virgo . Comprising approximately 1300 member galaxies, the cluster forms the heart of the larger Local Supercluster, of which the Local Group is an outlying member....
, Fornax Cluster
Fornax Cluster

At a distance of approximately 62.0 light-year , the Fornax Cluster is the second richest galaxy cluster within 100 million light-years, although it is much smaller than the Virgo Cluster....
, Abell 1689
Abell 1689

Abell 1689 is a galaxy cluster in the constellation Virgo . It is one of the biggest and most massive galaxy clusters known and acts as a gravitational lens, distorting the images of galaxies that lie behind it....
, Coma Cluster, amongst other clusters.

Partial list of dwarf galaxies

  • Aquarius Dwarf
    Aquarius Dwarf

    The Aquarius Dwarf galaxy is a dwarf galaxy and an irregular galaxy, that was first catalogued in 1959 by the DDO survey. Its most distinctive characteristic is that it is one of the few galaxies known to display a blueshift, as it is traveling towards the Milky Way at 137 km/s....
  • Canis Major Dwarf Galaxy
    Canis Major Dwarf Galaxy

    The Canis Major Dwarf galaxy is located in the same part of the sky as the constellation Canis Major. The galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one 1000000000 stars in all....
  • I Zwicky 18
    I Zwicky 18

    I Zwicky 18 is a dwarf irregular galaxy located about 59 million light years away. The galaxy was first identified by Swiss astronomer Fritz Zwicky in a 1930s photographic astronomical surveys of galaxies....
  • Irregular Galaxy IC 10
  • Large Magellanic Cloud
    Large Magellanic Cloud

    The Large Magellanic Cloud is a nearby galaxy, one thought to be a satellite galaxy of our own. At a distance of slightly less than 50 kiloparsecs , the LMC is the third closest galaxy to the Milky Way, with the Sagittarius Dwarf Spheroidal and Canis Major Dwarf Galaxy lying closer to the center of the Milky Way....
  • NGC 1569
    NGC 1569

    New General Catalogue 1569 is a dwarf galaxy irregular galaxy in Camelopardalis. While this faint galaxy is not a popular amateur astronomy target, it is well studied by professional astronomers, who are interested in the history of star formation within the galaxy....
  • NGC 1705
    NGC 1705

    NGC 1705 is a peculiar galaxy lenticular galaxy in the constellation Pictor. It is estimated to be approximately 17 million light-years from the Earth. It is a member of the Dorado Group....
  • Pegasus Dwarf Irregular Galaxy
    Pegasus Dwarf Irregular Galaxy

    The Pegasus Dwarf Irregular Galaxy is an irregular galaxy and a dwarf galaxy in the direction of the constellation Pegasus constellation. It was discovered by A.G....
  • Phoenix Dwarf
    Phoenix Dwarf

    The Phoenix Dwarf is a dwarf galaxy and an irregular galaxy that was discovered in 1976 by Hans-Emil Schuster and Richard Martin West and mistaken for a globular cluster....
  • Sagittarius Dwarf Elliptical Galaxy
    Sagittarius Dwarf Elliptical Galaxy

    The Sagittarius Dwarf Elliptical Galaxy is an elliptical loop-shaped satellite galaxy of the Milky Way Galaxy. The main cluster which, in 1994, was the first to be discovered, is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth and travelling in a polar orbit at a distance of about 50,000 light-yea...
  • Sagittarius Dwarf Irregular Galaxy
    Sagittarius Dwarf Irregular Galaxy

    The Sagittarius Dwarf Irregular Galaxy or SagDIG is a dwarf galaxy in the constellation of Sagittarius . It lies about 3.4 million light-years away....
  • Sculptor Dwarf Galaxy
    Sculptor Dwarf Galaxy

    The Sculptor Dwarf Galaxy is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the constellation Sculptor ....
  • Sculptor Dwarf Irregular Galaxy
    Sculptor Dwarf Irregular Galaxy

    The Sculptor Dwarf Irregular Galaxy is an irregular galaxy in the constellation Sculptor. The galaxy was discovered in 1976....
  • Sextans A
    Sextans A

    Sextans A , is a tiny dwarf galaxy irregular galaxy galaxy. It spans about 5000 light-years across, and is located within the Local Group of galaxies, which includes our Milky Way galaxy....
  • Sextans Dwarf
  • Small Magellanic Cloud
    Small Magellanic Cloud

    The Small Magellanic Cloud is a dwarf galaxy. It contains several hundred million stars.Some speculate that the SMC was once a barred spiral galaxy that was disrupted by the Milky Way to become somewhat irregular galaxy....
  • Tucana Dwarf
    Tucana Dwarf

    The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavrey of Mount Stromlo Observatory....
  • Ursa Minor Dwarf
    Ursa Minor Dwarf

    The Ursa Minor Dwarf dwarf elliptical galaxy was discovered by A.G. Wilson of the Lowell Observatory in 1954. It is part of the Ursa Minor constellation, and a satellite galaxy to the Milky Way....
  • Willman 1
    Willman 1

    Willman 1 or SDSS J1049+5103 is an extreme globular cluster or ultra low-mass dwarf galaxy. It is Galaxies named after people after Beth Willman of New York University, the lead author of a study based on the Sloan Digital Sky Survey data....
  • Carina Dwarf
    Carina Dwarf

    The Carina Dwarf Spheroidal is a dwarf galaxy in the Carina constellation. It was discovered in 1977 with the UK Schmidt Telescope. The Carina Dwarf is receding from the Milky Way at 230 km/s and is a satellite galaxy to the Milky Way....
  • Draco Dwarf
    Draco Dwarf

    The Draco Dwarf is a dwarf spheroidal galaxy which was discovered by Albert George Wilson of Lowell Observatory in 1954 on photographic plates of the National Geographic Society Palomar Observatory Sky Survey ....
  • Fornax Dwarf
    Fornax Dwarf

    The Fornax Dwarf Spheroidal is an elliptical dwarf galaxy in the constellation Fornax that was discovered in 1938 by Harlow Shapley. He discovered it while he was in South Africa on photographic plates taken by a 24 inch reflecting telescope at Boyden Observatory, shortly after he discovered the Sculptor Dwarf galaxy....
  • Leo II (dwarf galaxy)
    Leo II (dwarf galaxy)

    Leo II is an dwarf spheroidal galaxy about 690,000 light-years away in the constellation Leo . As of October 2008 it is one of 24 known satellite galaxies of the Milky Way....


See also


  • Galaxy morphological classification
  • List of nearest galaxies
    List of nearest galaxies

    This list includes all known galaxies within 3.6 MegaParsecs of Earth. This region of space encompasses all of our Local Group and reaches out to about the centre of the two largest nearby galaxy clusters - the M81 group of galaxies and Centaurus A/M83 Groups....


External links