VIRGOHI21
Sign in to saveVIRGOHI21 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.
Key facts
- Galaxy.name
- VIRGOHI 21
- Galaxy.epoch
- J2000
- Galaxy.constellation name
- Virgo
- Galaxy.dist_ly
- 50 Mly
- Galaxy.z
- 1966 km/s
- Galaxy.appmag_v
- < 27
- Galaxy.notes
- No stars
via Wikipedia infobox
Wikidata facts
- Part of
- Virgo Cluster
- Constellation
- Virgo
Show 6 more facts
- epoch
- J2000.0
- time of discovery or invention
- 2005-00-00
- right ascension
- 184.4625
- declination
- 14.7750
- radial velocity
- 1966
- catalog code
- VIRGOHI 21
Sources (1)
via Wikidata · CC0
~4 min read
Encyclopedic overview
6 sectionsContents
- Observational properties
- Dark galaxy interpretation
- Tidal tail interpretation
- See also
- References
- External links
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.
==Observational properties== VIRGOHI21 was detected through radio telescope observations of its neutral hydrogen 21 cm emissions. The detected hydrogen has a mass of about 100 million solar masses and is about 50 million light-years away. By analyzing the Doppler shift of the emissions, astronomers determined that the gas has a high velocity-profile width; that is, different parts of the cloud are moving at high speed relative to other parts. Follow-up Hubble Space Telescope deep observations of the region have detected very few stars (a few hundred).
Excerpted from Wikipedia’s “VIRGOHI21” article, available under the CC BY-SA 4.0 licence.