July 25 (UPI) -- New analysis suggests dark matter is cold and heavy, not light and fuzzy.
Scientists have yet to directly detect dark matter. What dark matter consists of exactly remains a mystery. Astronomers can only intimate its presence by measuring its gravitational influence.
Scientists do have theories as to what dark matter is like. The older theory posits that dark matter is cold and heavy, made up of large, slow-moving particles characterized by weak interactions with surrounding matter.
The cold dark matter theory helps explain why galaxies tend to cluster together, leaving massive voids in the cosmos. But the model also suggests the Milky Way should be surrounded by several hundred satellite galaxies. Only a few dozen galaxies orbit the Milky Way galaxy.
The fuzzy dark matter theory -- developed to fill holes in the cold dark matter theory -- posits that dark matter is made up of ultralight particles characterized by stronger interactions with surrounding matter. Fuzzy dark matter bounces wildly throughout the universe.
The behavior of matter across large scales is usually described by Newtonian physics, or the Standard Model of physics. But the large-scale movements of fuzzy dark matter can be described by quantum mechanics, which typically only describes the behavior of subatomic particles and minuscule scales.
Astronomers surveyed the intergalactic medium to determine which model best describes the vast galactic voids made up primarily of dark matter. In addition to dark matter, the intergalactic medium, or IGM, boasts small amounts of hydrogen gas and helium. The hydrogen absorbs small amounts of light emitted by distant objects, such as quasars.
Researchers developed a fresh model of the intergalactic medium using observations of quasar absorption throughout the cosmos. Their analysis showed large, heavy dark matter particles better explain quasar absorption in the IGM.
Researchers say its possible a fuzzy dark matter particle exists, but it can't explain the astronomical data -- galactic clustering and the light absorption of the IGM.
"For decades, theoretical physicists have tried to understand the properties of the particles and forces that must make up dark matter," lead author Vid Iršič, a postdoctoral astronomy researcher at the University of Washington, said in a news release. "What we have done is place constraints on what dark matter could be -- and fuzzy dark matter, if it were to make up all of dark matter, is not consistent with our data."