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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Interesting, but don't understand why they call it a galaxy. A galaxy is made up of stars, but they said this dark matter galaxy object has no stars...so why call it a galaxy then?
Forsooth, and the white matter is 'marshmallow'.
Yeah, I imagine when one keeps pointing out the invisible, it might have that result. ;-)
The most obvious reason would be that the apparent mass involved is of a magnitude that we associate with galaxies. I would also venture to guess that the theroretical formation process also gives rise to a structure that is similar to a "normal" galaxy (disk shaped with a central spherical bulge). So, it the same mass as a galaxy, and probably has the same shape as a galaxy, and we have no other word than "galaxy" to describe objects of that size and shape, so "galaxy" it is, until somebody invents a new term for it.
I hereby nominate "Phlirgoid" as the new sceintific term for a dark matter galaxy.....
This reminds me of my younger days, when black holes were still a fascinating theoretical construct, and not known to necessarily actually exist. Then confirmations of actual black holes in various parts of the universe began to flood in, and it was so exciting to realize that such bizarre, wild things were actually *real*.
Yeah, those black holes are really exciting - until you're sucked into the unescapable gravity well of one of 'em.... :-/
Thanks for the ping.
Gee. Thanks for clearing that up.
If you send me $10, the name of your choice will be recorded in a genuine, copyrighted book, "PatrickHenry's Official Guide to Dark Matter Names," which will filed with the Library of Congress! You will be given an official certificate, suitable for framing, to attest to your place in the history of the universe. What a keepsake for your family!
But don't delay. The supply of dark matter is limited. These objects are going fast. Name yours before they're all gone!
Bonus offer: For an extra $5, we will send you a diploma, awarding you a degree in Creation Science.
The cup is half full though. At the event horizon, as your time slows down, you get to see the universe unfold...
Imagine - all of your I told you so's being laid out in a fraction of a second...
I'd test the theory myself - but my schedule is full right now ;)
Neurons from entorhinal cortex (Limbic System)
Cortical pyramidal neurons from supragranular layers transfected with a plasmid that contained the green-fluorescent protein (GFP) gene coupled to a CMV promotor.
TS
A most precious find
Sometimes they see whatever will put the theory together, not matter how absurd.
The above pictures illustrate this comment, re: the Brain vs Protogalaxies.
What was seen is an inexhaustible reservoir of bogus RAT votes. These votes do possess mass (which is also bogus) and could exert serious influence, gravitational and otherwise.
And we all know what the brown stuff is! ;^)
HARDLY humorous. That's overpriced.
My cousin took cosmology at the local college and she still hasn't found a job.
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