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Sag DEG [1]
Observation data (J2000 epoch)
Right ascension 18h 55m 19.5s [2]
Declination−30° 32′ 43″ [2]
Redshift140 ± ? km/s [2]
Distance65 ± 7 kly (20 ± 2 kpc) [3][4]
TypedSph(t) [2]
Apparent dimensions (V)450′.0 × 216′.0 [2]
Apparent magnitude (V)4.5 [2]
Notable featuresHeading for a collision
with the Milky Way
Other designations
Sagittarius dwarf elliptical galaxy,[5] Sgr dSph,[2] Sagittarius dwarf spheroidal,[2] Sgr I Dwarf [2]
See also: Galaxy, List of galaxies
Messier 54, believed to be at the core of Sag DEG. Greyscale image from the HST's Advanced Camera for Surveys

Sag DEG is a small loop-shaped satellite galaxy of the Milky Way. It is known by other names, such as the Sagittarius dwarf elliptical galaxy or the Sagittarius dwarf spheroidal galaxy.

It consists of four globular clusters. The main cluster having been discovered in 1994. Sag DEG is about 10,000 light-years in diameter, and is about 70,000 light-years from Earth.

It moves in a polar orbit (i.e. an orbit passing through the galactic plane) at a distance of about 50,000 light-years from the core of the Milky Way (about 1/3 the distance of the Large Magellanic Cloud). In its looping, spiralling path, it has passed through the plane of the Milky Way several times in the past.[6]

Sag DEG should not be confused with the Sagittarius dwarf irregular galaxy, or the Sag DIG, a small galaxy 3.4 million light-years distant.

References[change | change source]

  1. "Name SDG". SIMBAD Astronomical Database. Retrieved 28 November 2006.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 "Saggitarius Dwarf Spheroidal". NASA/IPAC Extragalactic Database. Retrieved 28 November 2006.
  3. Karachentsev, I.D. et al (2004). "A catalog of neighboring galaxies". The Astronomical Journal 127 (4): 2031–2068. doi:10.1086/382905. 
  4. Karachentsev, I.D.; Kashibadze, O.G (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3–18. doi:10.1007/s10511-006-0002-6. 
  5. Sagittarius Dwarf Elliptical Galaxy / Sag DEG
  6. "Star-crossed: Milky Way's spiral shape may result from a smaller galaxy's impact". Scientific American. 14 September 2011.