The initial sighting of this
invisible object came in 2000, from radio wave observations made
using the Lovell telescope in Cheshire, England, which sketched
a cloud of hydrogen atoms a million times the mass of the sun
rotating in the Virgo cluster. Subsequent data from Puerto Rico's
Arecibo radio telescope confirmed the existence of the object,
dubbed VIRGOHI21. "From the speed it is spinning, we realized
that VIRGOHI21 was a thousand times more massive than could be
accounted for by the observed hydrogen atoms alone," commented
co-discoverer Robert Minchin of Cardiff University. This suggests
that abundant dark matter is lurking in the cloud. "If it
was an ordinary galaxy, then it should be quite bright and would
be visible with a good amateur telescope," he continued.
Previous claims for dark galaxies have crumbled after observations
using optical telescopes ultimately revealed resident stars.
But scrutinizing the region using the Isaac Newton optical telescope
in La Palma, Spain, revealed no visible stars.
Researchers have predicted the
existence of unseen galaxies in recent years, based on indications
that the universe contains far more matter than the visible variety
can account for. Indeed, the astronomers involved in this new
work noted that future surveys may well turn up many more dark
galaxies. These findings will be published in the Astrophysical
Journal.
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