Just found out today that radio astronomers have found the first ever galaxy (VIRGOHI21) composed entiredly of dark matter! For those that don't know dark matter was proposed originally to explain why galaxies rotate and move apart from each other much faster than can be explained by the visible amount of matter they contain.
Anyway it was found by a team of astronomers led by those at Cardiff University in the UK UK UK UK (cheers) using the Lovell telescope at Jodrell Bank. They found it using a technique where astrophysical objects are detected and analysed by looking at their hydrogen content only (this allows places where no large objects such as stars exist to be looked at - big advancements in this field recently).
They found it in the Virgo cluster (about 50million light-years away). It is rotating as a normal galaxy but but doesn't contain any stars or black holes. There is a cloud of hydrogen atoms there 10^8 times heavier than our sun. Robert Minchin and his team at Cardiff and co-workers in Italy, France and Austrailia have studied the galaxy in detail and all agree the galaxy is 1000 times more massive than can be accounted for by the hydrogen it contains! This was done by looking at the gravitational field etc around it - nothing at visible wavelengths of light have been deteced as would be if it were a normal galaxy! No stars detected, dead or otherwise. Nothing like this has been found ever before, the only similar things turned out to have stars or debris from nearby optical galaxies in them.
fs this is exciting Me goes to find the published paper - it's in Astrophys. J. 662 L21-L24 for any interested fellow scientists with access to that journal.
Anyway it was found by a team of astronomers led by those at Cardiff University in the UK UK UK UK (cheers) using the Lovell telescope at Jodrell Bank. They found it using a technique where astrophysical objects are detected and analysed by looking at their hydrogen content only (this allows places where no large objects such as stars exist to be looked at - big advancements in this field recently).
They found it in the Virgo cluster (about 50million light-years away). It is rotating as a normal galaxy but but doesn't contain any stars or black holes. There is a cloud of hydrogen atoms there 10^8 times heavier than our sun. Robert Minchin and his team at Cardiff and co-workers in Italy, France and Austrailia have studied the galaxy in detail and all agree the galaxy is 1000 times more massive than can be accounted for by the hydrogen it contains! This was done by looking at the gravitational field etc around it - nothing at visible wavelengths of light have been deteced as would be if it were a normal galaxy! No stars detected, dead or otherwise. Nothing like this has been found ever before, the only similar things turned out to have stars or debris from nearby optical galaxies in them.
fs this is exciting Me goes to find the published paper - it's in Astrophys. J. 662 L21-L24 for any interested fellow scientists with access to that journal.