VIRGOHI21
| VIRGOHI 21 | |
|---|---|
| Observation data (J2000 epoch) | |
| Constellation | Virgo |
| Right ascension | 12h 17m 53.6s |
| Declination | +14° 45′ 25″ |
| Redshift | 1966 km/s |
| Distance | 50 Mly |
| Apparent magnitude (V) | < 27 |
| Notable features | No stars |
VIRGOHI21 is an extended region of neutral hydrogen (HI) in the Virgo cluster discovered in 2005. Analysis of its internal motion indicates that it may contain a large amount of dark matter, as much as a small galaxy. Since VIRGOHI21 apparently contains no stars, this would make it one of the first detected dark galaxies. Skeptics of this interpretation argue that VIRGOHI21 is simply a tidal tail of the nearby galaxy NGC 4254.