NASA's Hubble Space Telescope and the Chandra X-ray Observatory provided clues that could help scientists finally identify mysterious dark matter.
The observations revealed dark matter does not slow down when colliding with itself, which narrows down the options of what the elusive substance could be, NASA reported.
Dark matter is an invisible substance that is believed to make up the majority of the universe, but the fact that it does not absorb or emit light has made it almost impossible to observe directly. The only way to detect the presence of dark matter is indirectly, such as through the way it distorts light from other sources in a phenomenon called gravitational lensing. To learn more about this mysterious matter a team of scientists watched what happened when it collided with galaxy clusters.
"Dark matter is an enigma we have long sought to unravel," said John Grunsfeld, assistant administrator of NASA's Science Mission Directorate in Washington. "With the combined capabilities of these great observatories, both in extended mission, we are ever closer to understanding this cosmic phenomenon."
Galaxy clusters are made up of "galaxies, gas clouds, and dark matter," and during galactic collisions the gas clouds slow down or stop altogether.
"We know how gas and stars react to these cosmic crashes and where they emerge from the wreckage. Comparing how dark matter behaves can help us to narrow down what it actually is," said the study's lead author David Harvey of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland.
The researchers looked at 72 large cluster collisions and observed that during these events the dark matter continued through unfazed, meaning it did not react with the visible particles as much as previously believed. The researchers were able to determine this because if the dark matter had reacted with itself, it would have caused the distribution of galaxies to shift.
These findings have narrowed down the possibilities of what dark matter could be made of because materials are now ruled out that create a strong frictional force.
"There are still several viable candidates for dark matter, so the game is not over. But we are getting nearer to an answer," Harvey said. "These astronomically large particle colliders are finally letting us glimpse the dark world all around us, but just out of reach."
The findings were published in a recent edition of the journal Science.
