Posted on 02/23/2005 4:11:58 PM PST by AntiGuv
Astronomers have discovered an invisible galaxy that could be the first of many that will help unravel one of the universe's greatest mysteries. The object appears to be made mostly of "dark matter," material of an unknown nature that can't be seen.
Theorists have long said most of the universe is made of dark matter. Its presence is required to explain the extra gravitational force that is observed to hold regular galaxies together and that also binds large clusters of galaxies. Theorists also believe knots of dark matter were integral to the formation of the first stars and galaxies. In the early universe, dark matter condensed like water droplets on a spider web, the thinking goes. Regular matter -- mostly hydrogen gas -- was gravitationally attracted to a dark matter knot, and when the density became great enough, a star would form, marking the birth of a galaxy. The theory suggests that pockets of pure dark matter ought to remain sprinkled across the cosmos. In 2001, a team led by Neil Trentham of the University of Cambridge predicted the presence of entire dark galaxies. One of perhaps many The newfound dark galaxy was detected with radio telescopes. Similar objects could be very common or very rare, said Robert Minchin of Cardiff University in the UK. "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," Minchin told SPACE.com.
In a cluster of galaxies known as Virgo, some 50 million light-years away, Minchin and colleagues looked for radio-wavelength radiation coming from hydrogen gas. They found a well of it that contains a hundred million times the mass of the Sun. It is now named VIRGOHI21. The well of material rotates too quickly to be explained by the observed amount of gas. Something else must serve as gravitational glue. "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," Minchin said. "If it were an ordinary galaxy, then it should be quite bright and would be visible with a good amateur telescope." 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." Long road to discovery Other potential dark galaxies have been found previously, but closer observations revealed stars in the mix. Intense visible-light observations reveal no stars in VIRGOHI21. The invisible galaxy is thought to lack stars because its density is not high enough to trigger star birth, the astronomers said. The discovery was made in 2000 with the University of Manchester's Lovell Telescope, and the astronomers have worked since then to verify the work. It was announced today. "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," said astronomer Jon Davies of Cardiff University in the UK. It's a really exciting discovery." Additional radio observations were made with the Arecibo Observatory in Puerto Rico. Follow-up optical work was done with the Isaac Newton Telescope in La Palma. Astronomers from the UK, France, Italy and Australia contributed to the research. The project is now searching for other possible dark galaxies. Dark matter makes up about 23 percent of the universe's mass-energy budget. Normal matter, the stuff of stars, planets and people, contributes just 4 percent. The rest of the universe is driven by an even more mysterious thing called dark energy.
Images
The ellipse shows the region of sky where the dark galaxy was found. Credit: Cardiff University/Isaac Newton Telescope on La Palma
NGC 7479 is the type of galaxy astronomers would have expected to see based on the measurements taken. Credit: Nik Szymanek/Faulkes Telescope North, Maui, copyright FTLLC
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shady ping!
A most significant discovery.
Dark matter, dark energy - stay away from the dark side!
What part of "invisible" did I miss?
Are they now visible.
Paging Art Bell . . .
Maybe they discovered Heaven. I just wonder if it is a physical place that can be discovered. Maybe the dark matter is in a different dimension or something. The advances by astronomers in the past 30 years or so is just amazing.
Good idea. Ping!
I knew about thse galaxies long ago, and kept pointing them out to people; but they said I was nuts.
So if you were on a planet in this dark galaxy, would it suck your tan off of you?
Duplicate post:
http://www.freerepublic.com/focus/f-news/1349621/posts?page=32#32
My reply on that thread was that they had discovered an invisible galaxy (right!) but couldn't invent calorie free cheesecake? Wassup?
Are they sure? Maybe they just forgot to take the lens cap off of their telescope.
Probably not, but that is an integral part of the definition of a theory. Observations show that objects are behaving differently than, in this case, known (and to a large extent proven) physics can can describe. The result is either the known physics (in this case basic gravity) is wrong, or something else with currently unobservable mass is in play in the observations.
This theory relies on well known laws of gravitational attraction, but observations said there ain't enough mass to do what has been repeatedly observed. So either apples fall up in some places, or there is more mass than what can be observed. The theory is that there is more mass than could be observed.
Now, through new methods, inferences, or whatever (I'm not a cosmologist, astrophysicist, or even very cosmopolitan) researchers think they have "seen" dark matter.
These results support the theory. If they had been different, they could have forced a change in the theory.
And, that's what it's all about..
WOW! They found Hillary's brain!!
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Opps! I searched for it but didn't come up with anything. It's a different version of the news, however, so I guess it's alright.
If it's not recorded in the Jedi library catalog, it doesn't exist.
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