Virgo Stellar Stream

  • Quasar Equatorial Survey Team / Vivas et al., 2001
  • Newberg et al. 2,002
  • Juric et al., 2008

Virgo Stellar Stream:

  • Duffau et al. 2,006

The Virgo Over -density (VOD, Eng. Overabundance of Virgo ) is a region of the sky with an increased density of stars in the constellation Virgo. The nature of the phenomenon is still unclear and is the subject of current research. Many observations indicate that it is the remains of a spheroidal dwarf galaxy that merged with the Milky Way straight. A matching structure is known as the Virgo Stellar Stream (VSS, Eng. Stream for the Virgo / Virgo stellar stream ). What is the relationship the objects known as Virgo and Virgo Stellar Stream Over Density stand out is yet to be determined, but there are indications that it is coherent structures with a common origin. An alternative explanation for the Virgo Over -density would be that it is a large-scale structure of the stars of the galactic halo.

Discovery

The current was discovered by analysis of photometric data of the survey of the Sloan Digital Sky Survey (short SDSS) that created a three-dimensional map of the Milky Way using the color-magnitude relation and certain standard candles to estimate their distance ( Photometric parallax)

The first proposal of a new galaxy in the constellation Virgo (Virgo ) was made team in 2001 due to data of the Quasar Equatorial Survey. Within this project, stars searched using the 1.0 -meter Schmidt telescope at the Observatorio Nacional de Llano del Hato Astronómico in Venezuela after RR Lyrae. Five of these variable stars were found in a pile at the coordinates near the right ascension 12h 24m. The astronomers of the project attended then, that it is at this accumulation around a small dwarf galaxy that is cannibalized by our own Milky Way ( " 12.4 hour clump ").

Properties

The Virgo Over -density has an area of ​​at least 2000 square degrees; its actual extent is probably about 3000 square degrees of the celestial sphere ( in about 15 % of the night sky ). Despite the considerable angular extent it contains only a few hundred thousand stars. The low surface brightness ( only about 32.5 mag/arcmin2 ) affected the discovery in surveys before the SDSS considerably. The number of stars is barely superior to that of a typical globular cluster and the Virgo dwarf was described by one member of the discovering team as " pretty sickly Galaxy " compared to our Milky Way.

Many of their stars have been known for centuries and were held for members of the Milky Way itself, although at least their low metallicity made ​​them look weird compared to the other stars of the Milky Way.

The Virgo Over -density lies within the Milky Way, about 10 kpc (or 30,000 light years) from the Sun and extends over a region of space with at least 10 kpc in diameter. It lies near the plane of the Sagittarius dwarf galaxy, which in 1994 could be identified by a similar photometric survey. The Sagittarius dwarf is a small dwarf galaxy that merged with the Milky Way. However, it is about 4 times farther away. Thus, it seems unlikely that these two are physically coupled directly, although it seems possible that the Virgo stream represents a tidal - remnant on the path of the disintegrating Sagittarius dwarf galaxy on its orbit around the Milky Way.

The cloud-like morphology of the Virgo Over -density differs significantly from that of star streams such as the Monoceros Ring, which was discovered in 2002 and is considered the tidal rest of the Canis Major dwarf galaxy that merged with the Milky Way.

More

  • Tidal power
  • Star power
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