Dark matter galaxy discovered
Dark Matter: a hypothetical form of matter that is believed to make up 90 percent of the matter in the universe; it is invisible (does not absorb or emit light) and does not collide with atomic particles but exerts gravitational force
The first galaxy composed predominately of dark matter seems to have been discovered by a group of stronomers led by Dr. Robert Minchin at Cardiff University, UK, using a 76-metre Lovell radio telescope at the University of Manchester’s Jodrell Bank Observatory VIRGOHI21, 50 million light-years away in the Virgo cluster, was visible at radio frequencies (despite the space.com article calling this invisible) through the emissions from clouds of hydrogen gas. The hydrogen observed seems to account for 1000 times less mass than the galaxy as a whole, as determined by the rotation rate of the hydrogen clouds; nevertheless, there’s nothing visibly present at that distance at all.
This was part of a search for “dwarf” galaxies, which are predicted to be present in the universe at much greater frequencies than so far observed. But while it has no stars, this galaxy is not a dwarf. Other “dark matter” galaxies have been found in the past, but all had at least a few stars, though in one case (dwarf galaxy I Zwicky 18) all the observed stars were less than 500,000 years old, a tiny fraction of the normal billions of years.
It’s possible this observation is just a coincidence caused by two hydrogen clouds passing one another at high speed, rather than a single rotating mass of hydrogen. Nevertheless, we know the universe is mostly made of dark matter - it’s got to be out there somewhere, and this may be the first real evidence where.
Atronomers claim first “dark galaxy” find, NewScientist.com
A galaxy with no stars, SciScoop.com