A recent article from SPACE.com via Yahoo! News. A part of the article:
How hot is dark matter?
In the 1960s and 1970s, astronomers hypothesized that there might be more mass in the universe than what is visible. Vera Rubin, an astronomer at the Carnegie Institution of Washington, studied the speeds of stars at various locations in galaxies. [Top 10 Strangest Things in Space]
Rubin observed that there was virtually no difference in the velocities of stars at the center of a galaxy compared to those farther out. These results seemed to go against basic Newtonian physics, which implies that stars on the outskirts of a galaxy would orbit more slowly.
Astronomers explained this curious phenomenon with an invisible mass that became known as dark matter. Even though it cannot be seen, dark matter has mass, so researchers infer its presence based on the gravitational pull it exerts on regular matter.
Dark matter is thought to make up about 23 percent of the universe, while only 4 percent of the universe is composed of regular matter, which includes stars, planets and humans.
"Scientists still don't know what dark matter is, but that could soon change," Cho wrote. "Within years, physicists might be able to detect particles of the stuff."
But while astronomers may soon be able to detect particles of dark matter, certain properties of the material remain unknown.
"In particular, studies of runty 'dwarf galaxies' might test whether dark matter is icy cold as standard theory assumes, or somewhat warmer essentially a question of how massive particles of dark matter are," Cho explained.
8 Modern Astronomy Mysteries Scientists Still Can't Explain
Edited by Chuck77, : No reason given.
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