DDO 190

DDO 190 (or UGC 9240) is a dwarf irregular galaxy in the vicinity of the Milky Way, as it is relatively small and lacks clear structure. It is 9.10 million light-years (2.79 Mpc) away from Earth and lies out of the Local Group, determined by the tip of the red giant branch method.[1] The outskirts of the galaxy are harbouring older (reddish) stars, while the centre is crowded with younger (bluish) stars. Heated gas is observed at several places.[2] DDO 190 still experiences some active star formation. The galaxy is categorised as a Magellanic dwarf galaxy of morphological type Im. Its metallicity is [Fe/H] = −1.55 ± 0.12.[1]

DDO 190
The dwarf galaxy with pockets of ionised gas, seen as blue
Credit: ESA, Hubble and NASA
Observation data
Right ascension14h 24m 00s
Declination44° 30′ 00″
Distance9.10×10^6 ly (2.79 Mpc)h−1
0.73
Group or clusterM94 Group
Apparent magnitude (V)13.25
Absolute magnitude (V)-14.19
Characteristics
TypeIAm
Mass5×107 M☉

DDO 190 is small, but not tiny: about 15,000 light years across—about 1/6 the size of our galaxy. It is also well outside the Local Group, which contains nearby galaxies (the Andromeda galaxy is less than 3 million light years distant from Earth, for comparison), and is instead thought to be part of the M94 galaxy group. But if true it is fairly isolated even from the others on its team; the nearest neighbor appears to be another dwarf galaxy, DDO 187, at a distance of 3 million light-years (0.92 Mpc).[2]

History

The galaxy was discovered by the Canadian astronomer Sidney van der Bergh in 1959 and put in the DDO catalogue.[2]

References
  1. Battinelli, P.; Demers, S. (2006). "The C star population of DDO 190" (PDF). ESO. Bibcode:2006A&A...447..473B. doi:10.1051/0004-6361:20052829. Archived from the original (PDF) on 2014-11-10. Retrieved 2012-08-18. The HI mass of DDO 190, estimated at 5 × 107 solar masses by Stil & Israel (2002a) is normal for a galaxy of its luminosity.
  2. "Galactic Island". NASA. 2012-08-17. Archived from the original on 2012-08-17. Retrieved 2012-08-18.


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