"WASHINGTON (AFP) - US astronomers on Tuesday presented the most solid proof yet of the existence of dark matter, a mysterious substance believed to make up more than a quarter of the universe.

Astronomers using the Hubble Space Telescope spotted a ring of dark matter in a galaxy cluster some five billion light-years away from Earth, which measured some 2.6 million light-years across."

http://news.yahoo.com/s/afp/20070515/ts_alt_afp/usspacematter;_ylt=ApJm54w8Iq6zzG9BRGc8cJYXIr0F

Dark matter may be dark, but is it invisible?

Amaranth: "Dark matter may be dark, but is it invisible?"

For now, at least. It doesn't emit any detectable electromagnetic radiation (including light), and can be detected only by its gravitational effects, e.g. on galaxy rotation, and by gravitational lensing (as in the case cited above).

"dark matter is all around us - it goes through us all the time without us noticing" - nobody's proved that, but maybe its a fair assumption.

http://www.sciencedaily.com/releases/2007/04/070419130004.htm
April 22, 2007