Canis Major Dwarf Galaxy

Canis Major Dwarf
Observation data (J2000 epoch)
Constellation	Canis Major
Right ascension	07^h 12^m 35.0^s[1]
Declination	−27° 40′ 00″[1]
Distance	25,000 ly
Characteristics
Type	Irr
Apparent size (V)	12 degrees × 12 degrees
Notable features	-
Other designations
CMa Dwarf,[1] PGC 5065047

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.

The supposed small galaxy has a relatively high percentage of red giant stars. It is thought to have about one billion stars in all.

The Canis Major Dwarf is an irregular galaxy. It may be the closest neighbouring galaxy to us 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 Sag DEG, the previous contender for closest galaxy to us.

Discussion

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]

References

1. "NASA/IPAC extragalactic database". Results for Canis Major dwarf. Retrieved 2007-03-16.
2. "Astronomers find nearest galaxy to the Milky Way". Archived from the original on May 27, 2008. Retrieved 2009-09-24.
3. Martin N.F.; et al. (2004). "A dwarf galaxy remnant in Canis Major: The fossil of an in-plane accretion on to the Milky Way". Monthly Notices of the Royal Astronomical Society. 348 (1): 12–23. arXiv:astro-ph/0311010. Bibcode:2004MNRAS.348...12M. doi:10.1111/j.1365-2966.2004.07331.x. S2CID 18383992.
4. Lopez-Corredoira, M.; Moitinho, A.; Zaggia, S.; Momany, Y.; Carraro, G.; Hammersley, P. L.; Cabrera-Lavers, A.; Vazquez, R. A. (Jul 2012). "Comments on the "Monoceros" affair". arXiv:1207.2749 [astro-ph.GA].
5. Momany, Y.; Zaggia, S. R.; Bonifacio, P.; Piotto, G.; De Angeli, F.; Bedin, L. R.; Carraro, G. (July 2004). "Probing the Canis Major stellar over-density as due to the Galactic warp". Astronomy and Astrophysics. 421 (2): L29 – L32. arXiv:astro-ph/0405526. Bibcode:2004A&A...421L..29M. doi:10.1051/0004-6361:20040183. S2CID 6371010.
6. Mateu, Cecilia; et al. (2009). "No excess of RR Lyrae stars in the Canis Major Overdensity". The Astronomical Journal. 37 (5): 4412–23. arXiv:0903.0376. Bibcode:2009AJ....137.4412M. doi:10.1088/0004-6256/137/5/4412. S2CID 18967866.