Dark Matter

Dark matter makes up approximately 25 percent of the universe but, as the name implies, is largely mysterious at this point. It doesn’t emit or absorb light and so cannot been seen with telescopes. It has never been detected directly.

So why do we think it exists? Observers in the 1930s started noticing galaxies rotating within galaxy clusters in a way that indicated significantly more gravity than the galaxy’s visible mass would exert. Discoveries since then have convincingly advanced the idea that a mysterious, gravity-exerting mass encircles the centers of galaxies and affects the speed of objects in their orbit.

The search for dark matter is a major focus at CCAPP, where scientists use a variety of tools in their pursuit, including experiments, computer simulations, and regular pencil and paper.

Faculty, postdoctoral fellows and graduate students have used data from Hubble and other telescopes to explore dark matter through gravitational lensing—the extent to which a galaxy cluster’s gravity deflects light from an object that’s on the opposite side of the cluster from Earth. By comparing galaxy clusters’ observable mass and their gravitational effect on light around them, scientists at CCAPP have been able to compute the amount of dark matter present and learn more about its characteristics.

CCAPP astrophysicists also study dark matter by running computer simulations on the Center’s share of the Ohio Supercomputer Center’s powerful Ruby cluster, while others search for evidence of new particles using data from the underground Large Hadron Collider and satellites orbiting Earth. In the same way the Higgs boson’s existence was predicted before its discovery, CCAPP physicists are optimistic that the LHC, with its higher-than-ever energy levels, is capable of producing dark matter.

While dark matter is still largely a mystery, most astroparticle physicists agree that it likely consists of one or more unidentified subatomic particle species. In addition to its gravitational effects, we also know that dark matter’s lifetime appears to be longer than the age of the universe, and it should be electrically neutral.

Through work at CCAPP and around the world, we get ever closer to identifying this elusive matter.

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