Canis Major dwarf

disputed irregular galaxy located near the constellation Canis Major

The Canis Major dwarf galaxy (CMa dwarf) or Canis Major overdensity (CMa overdensity) is a disputed dwarf irregular galaxy in the Local Group. It is in the same part of the sky as the constellation Canis Major.

Canis Major dwarf
Observation data (J2000 epoch)
ConstellationCanis Major
Right ascension 07h 12m 35.0s[1]
Declination−27° 40′ 00″[1]
Distance25,000 ly
Apparent size (V)12 degrees × 12 degrees
Notable features-
Other designations
CMa Dwarf,[1] PGC 5065047
See also: Galaxy, List of galaxies

The supposed small galaxy contains a relatively high percentage of red giant stars, and is thought to contain an estimated one billion stars in all.

The Canis Major dwarf is classified as an irregular galaxy. It is now thought to be the closest neighbouring galaxy to our position in the Milky Way. It is about 25,000 light-years away from the Solar System,[2] and 52,000 light-years from the Galactic centre. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius dwarf elliptical galaxy, the previous contender for closest galaxy to us.


The dwarf was discovered in 2003.[3]

Several studies cast doubts on the true nature of this overdensity.[4][5] Investigation of the area in 2009 showed only ten RR Lyrae variable stars. This is consistent with the Milky Way's halo and thick disk populations, rather than a separate dwarf spheroidal galaxy.[6]


  1. 1.0 1.1 1.2 "NASA/IPAC extragalactic database". Results for Canis Major dwarf. Retrieved 2007-03-16. CS1 maint: discouraged parameter (link)
  2. "Astronomers find nearest galaxy to the Milky Way". Archived from the original on May 27, 2008. Retrieved 2009-09-24. CS1 maint: discouraged parameter (link)
  3. Martin N.F.; et al. (Nov 2003). "A dwarf galaxy remnant in Canis Major: the fossil of an in-plane accretion onto the Milky Way".
  4. "Comments on the "Monoceros" affair". Jul 2012.
  5. "Probing the Canis Major stellar over-density as due to the Galactic warp". July 2004.
  6. Mateu, Cecilia; et al. (2009). "No excess of RR Lyrae stars in the Canis Major Overdensity". The Astronomical Journal. 37 (5): 4412–23. Bibcode:2009AJ....137.4412M.