BEIJING, Feb. 25 (Xinhuanet) -- Astronomers have discovered the first ever invisible galaxy made up almost entirely of dark matter.
The galaxy, named VIRGOHI21, was found lying in the Virgo cluster 50 million light years away using the University of Manchester's Lovell Telescope in Cheshire and confirmed with the Arecibo telescope in Puerto Rico.
While it contains mass that rotates like a normal galaxy, it contains no stars.
This mysterious form of matter does not emit or absorb electromagnetic radiation -- hence the name "dark" -- and can only be detected by its gravitational influence on ordinary matter. Overall the universe is though to contain about 5% of ordinary matter, 25% of dark matter and 70% of dark energy. Although various types of new particle have been proposed to explain the dark matter, the nature of the dark energy remains a complete mystery.
"If they are the missing dark matter halos predicted by galaxy formation simulations but not found in optical surveys, then there could be more dark galaxies than ordinary ones," Robert Minchin of Cardiff University in the UK was quoted as saying by SPACE.com.
The ratio of dark matter to regular matter is at least 500-to-1, which is higher than I would expect in an ordinary galaxy," Minchin said. "However, it is very hard to know what to expect with such a unique object -- it may be that high ratios like this are necessary to keep the gas from collapsing to form stars."
The find is considered important because cosmological models suggest that dark matter is five times more abundant than baryonic matter in the Universe yet is difficult to study from Earth because of the planet's proximity to the Sun.
"The Universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way," says Jon Davies of Cardiff. "It's a really exciting discovery." Enditem
http://news.xinhuanet.com/english/2005-02/25/content_2617501.htm
The galaxy, named VIRGOHI21, was found lying in the Virgo cluster 50 million light years away using the University of Manchester's Lovell Telescope in Cheshire and confirmed with the Arecibo telescope in Puerto Rico.
While it contains mass that rotates like a normal galaxy, it contains no stars.
This mysterious form of matter does not emit or absorb electromagnetic radiation -- hence the name "dark" -- and can only be detected by its gravitational influence on ordinary matter. Overall the universe is though to contain about 5% of ordinary matter, 25% of dark matter and 70% of dark energy. Although various types of new particle have been proposed to explain the dark matter, the nature of the dark energy remains a complete mystery.
"If they are the missing dark matter halos predicted by galaxy formation simulations but not found in optical surveys, then there could be more dark galaxies than ordinary ones," Robert Minchin of Cardiff University in the UK was quoted as saying by SPACE.com.
The ratio of dark matter to regular matter is at least 500-to-1, which is higher than I would expect in an ordinary galaxy," Minchin said. "However, it is very hard to know what to expect with such a unique object -- it may be that high ratios like this are necessary to keep the gas from collapsing to form stars."
The find is considered important because cosmological models suggest that dark matter is five times more abundant than baryonic matter in the Universe yet is difficult to study from Earth because of the planet's proximity to the Sun.
"The Universe has all sorts of secrets still to reveal to us, but this shows that we are beginning to understand how to look at it in the right way," says Jon Davies of Cardiff. "It's a really exciting discovery." Enditem
http://news.xinhuanet.com/english/2005-02/25/content_2617501.htm
