Astronomy Magazine

Dwarf Galaxies

Posted on the 09 May 2011 by Gabe12logan
In the immediate neighborhood of our Galaxy system a few more small satellite galaxies was found, the so-called elliptical spheroids that can be considered as the companions of the Milky Way. Although they were close, due to their low surface brightness, they were difficult to detect. The first dwarf galaxy was discovered in 1937th from Harvard's Observatory in Boyden (South Africa). It was detected in constellation Sculptor, and because of that is called Sculptor dwarf galaxy. The first observations showed that this is a dwarf galaxy composed of a very weak stars. Brightest stars were red and somewhat similar to the stars which form globular clusters. However, unlike globular clusters, density of this star system is very small compared to its size. System in the Sculptor is 260 000 ly away from us.
Later it was discovered a few of these spheroids, such as a system in Fornax located 450 000 light years away, dwarf galaxies in the constellations Draco and Ursa Minor constellations, known for Barnard's galaxy, and the farthest satellite spheroids Leo I and Leo II, and many others. Stellar populations that we observe in these strange dwarf galaxies are similar to those in elliptical galaxies. However, they have very few stars, between 100 000 and several millions. This means that their masses are not much larger than the masses of globular clusters in the Milky Way. Most of these galaxies is dead, all the stars in them are very old, and there is no indication of the creation of new stars. The explanation can be found in a small mass and density, in the Milky Way stars are born from gas discharging older stars, and in these dwarfs there is no enough mass, and there is no enough gravity which would maintained the gas.
At a distance of only 78 000 light years away, hidden behind the center of our galaxy, are the remains of tiny dwarf galaxies called Sagittarius Dwarf, which in the past collides with our galaxy. Tidal forces of the Milky Way spread the dwarf galaxy, and today only its compact center can be recognize. The diameter of the remains of this galaxy is, after the longest axis, a quarter of the diameter of the Milky Way. But the mass of this galaxy is only one thousandth of the mass of our galaxy. It is estimated that the stars of the Sagittarius dwarf galaxy will merge in the Milky Way within the next 100 million years. Some astronomers believe that the halo of our galaxy originated due to a number of such collisions with dwarf galaxies and many globular clusters are actually newcomers from other galaxies.

You Might Also Like :

Back to Featured Articles on Logo Paperblog

These articles might interest you :

  • Ring Galaxies

    Ring galaxy is a galaxy, which in form resembles the ring. Ring galaxies are composed of massive, relatively young blue stars that are extremely bright. The... Read more

    By  Gabe12logan
  • Local Group Of Galaxies

    The local group is relatively small cluster of galaxies and our galaxy is a part of local group. It consists of two dozen galaxies, but most are "dwarf"... Read more

    By  Gabe12logan
  • Radio Galaxies

    are galaxies that are extremely bright in the radio part of the spectrum. In the majority of detected radio galaxies a strong emission of radio waves was found... Read more

    By  Gabe12logan
  • Dwarf Planet Eris

    Eris, 136 199 Eris, is the largest known dwarf planet and for now the largest body found in Kuiper Belt. Although his discoverers initially declared him as the... Read more

    By  Gabe12logan
  • New Fanged Dwarf Dinosaur Found

    Fanged Dwarf Dinosaur Found

    A new study of Pegomastax africanus, a 2-foot-long (0.6-meter-long) heterodontosaur that lived about 200 million years ago tells that this new,... Read more

    By  Ningauble
  • Plant of the Week: Miscanthus Sinensis ‘Yakushima Dwarf’

    Plant Week: Miscanthus Sinensis ‘Yakushima Dwarf’

    Miscanthus sinensis 'Yakushima Dwarf' flower (28/07/2011, London) Position: Full sun Soil: Moist, well drained soil Flowering period: Late summer to autumn... Read more

    By  Davis Landscape Architecture
  • Under Threat - The Dwarf Wedgemussel

    Under Threat Dwarf Wedgemussel

    The Dwarf Wedgemussel is a small-sized and rare species of freshwater mussel that is only found inhabiting the streams and rivers along North America's... Read more

    By  Azanimals