Canis Major Dwarf Galaxy

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Galaxy
Canis Major Dwarf Galaxy
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AladinLite
Constellation Big dog
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 07 h 12 m 35 s
declination −27 ° 40 ′ 00 ″
Appearance
Angular expansion 720 ′ × 720 ′
Physical data
Affiliation Local group  
distance 25,000  ly  
history
discovery A team of astronomers from
France , Italy , UK and
Australia
Discovery date 2003
Catalog names

The Canis Major dwarf galaxy in the constellation Canis Major ( Latin Canis Major ) is the present state of research, the next neighbor galaxy of the Milky Way . It is 42,000  light years from the center of the Milky Way ; that's only about 80 percent of the distance to the Sagittarius dwarf galaxy , which was considered the closest neighbor of the Milky Way before the Canis Major galaxy was discovered.

The Canis Major dwarf galaxy is about 25,000 light years away from the  solar system . The solar system is therefore just closer to the Canis Major dwarf galaxy than to the center of the Milky Way (approx. 27,000 light years).

Astronomical context

The number of single stars in this galaxy is estimated at around one billion. Its core is elliptical in shape, but the galaxy as a whole is categorized as an irregular galaxy . It is practically right on the galactic plane .

If you compare the distance of the galaxy from the center of the Milky Way with the radius of the Milky Way, you can see that it is practically within the outer parts of the Milky Way. The tidal forces that the Milky Way exerts on this dwarf galaxy are therefore extremely high, and in fact the Canis Major galaxy appears to be in the process of disintegrating and has already been significantly deformed.

discovery

Position of the Canis Major dwarf galaxy (black border) in the constellation Great Dog

Due to its location in the galactic plane, the galaxy remained undiscovered until 2003 , on the one hand because the interstellar matter blocks the view of the galaxy, on the other hand because it is difficult to distinguish from the Milky Way itself. The discovery was made by an international team as part of the Two Micron All Sky Survey , which was carried out in the infrared range , in which the interstellar matter is more transparent than in the optical range.

Related phenomena

In the wake of the discovery of the Canis Major Galaxy, other strange occurrences in the vicinity of the constellation Great Dog, some of which had been known for some time, could be associated with this galaxy and its disintegration phenomena.

  • A strange cluster of globular clusters in an area of ​​the sky where there are otherwise very few such clusters. These include the long-known objects M79 , NGC 1851 , NGC 2298 and NGC 2808 , all of which were probably part of the former globular star cluster system of the dwarf galaxy.
  • An oversized density of giant stars of the spectral type  M, which was also discovered during the Two-Micron All Sky Survey . These excess stars seem to come from the dwarf galaxy, which has a high proportion of red giant stars .
  • A long filament of stars along the orbit of the dwarf galaxy, which was discovered during the Sloan Digital Sky Survey in 2001 , named the Monoceros Ring , and winds around the Milky Way up to three times.
  • Some open star clusters , including Dol 25, H 18 and AM 2, that may have been formed in this area by the tidal action of the dwarf galaxy on the interstellar gas of the Milky Way.

Alternative interpretation

In astronomical research there is also talk of Canis Major Overdensity , because despite strong indications it cannot yet be considered certain whether the observed clusters actually come from a separate galaxy or are attributable to the Milky Way itself.

Web links

Commons : Constellation Greater Dog  - Collection of images, videos and audio files

Individual evidence

  1. ↑ NASA / IPAC Extragalactic Database
  2. ↑ a b SEDS