Dark Matter

Prior to July, 1995 ZetaTalk stated that a massive amount of tiny matter, not Dark Matter, was the largest component in the Universe. On January 6, 1999, the AAS presented evidence that dark matter galaxies, called Ghost Galaxies, outnumber and outweigh luminous galaxies, and on April 6, 2000 the Associated Press confirmed that the tiny matter conclusion was being adopted by scientists.

Ghost Galaxies
American Astronomical Society, January 6, 1999

Astronomers suggest that there may be a large number of dark galaxies. In fact, galaxies made almost entirely of dark matter may outnumber luminous galaxies like our Milky Way.

This conclusion is based on a study of dark matter properties in 43 galaxies ranging from the most luminous spirals to the faintest galaxies known. It shows that dark matter properties correlate with luminosity and that it is normal for the smallest galaxies, which contain just a faint scatter of stars, to have high densities of dark matter. These galaxies look gossamer, but they are like cannonballs: they contain a much higher density of dark matter than do giant galaxies. Almost-dark galaxies like these are the most common ones known. Darker galaxies - ones with too few stars to be discovered - may be more common still.

These results are being presented today at the 193rd Meeting of the American Astronomical Society in Austin, Texas, by John Kormendy of the University of Hawaii and Kenneth C. Freeman of the Australian National University and Mount Stromlo Observatory.

Scientists beginning to shed light on dark matter
By Matthew Fordahl, Associated Press, April 6, 2000

The invisible and so far unidentified dark matter that accounts for 90 percent of the universe could soon be brought to light as scientists develop sensitive detectors capable of sniffing out tiny particles predicted by theory but not yet proven to exist. Teams of researchers are racing to build the devices even though they might be hunting for something that occurs only in the minds of theoretical physicists. If so, a generation of theories can be tossed out. But if the weakly interacting massive particles - WIMPs - are detected, the finding could solve fundamental mysteries of the universe: how it formed after the Big Bang, the nature of its structure and whether it will all end in a Big Crunch. "It will certainly be one of the great discoveries in the history of science," said physicist Joel Primack of the University of California, Santa Cruz. "It will be a window on a completely different aspect of the universe."

Astronomers have known for 70 years that visible matter is only a small part of the universe. Something that exerts a strong gravitational tug, for instance, causes the outer stars of a spiral galaxy to revolve faster than they should, given what is visible. Other dark matter possibilities have been ruled out. Dead stars, large planets and black holes, once thought to be leading candidates, are now considered unlikely. Weighty but ghostly WIMPs are currently the prime suspects. Physicists theorize that the tiny particles originated during the Big Bang, but they only interact weakly with the protons and neutrons of the visible universe. If real, 10 trillion WIMPs may be zipping through every 2 pounds of matter here on Earth every second. A dozen experiments worldwide are based on the assumption that occasionally a WIMP might smack into normal matter. But the challenge has been to differentiate them from other particles that zip through the cosmos.