UA Astronomy Professor Attracting International Attention With Theory Related to Dark Matter Mystery

TUSCALOOSA, Ala. – A recently published paper, co-authored by an adjunct professor in The University of Alabama department of physics and astronomy, is attracting international attention with its theory related to “dark matter,” invisible material believed to comprise a large portion of the universe and whose content scientists have long sought.

The paper published March 8 in Physical Review Letters, and astronomers are clamoring for its authors, Dr. Peter Biermann, the UA adjunct professor, who is also a professor at Bonn University and head of a theory group at the Max-Planck-Institute for Radioastronomy, both in Germany, and Dr. Alexander Kusenko, associate professor of physics and astronomy at UCLA, to make related presentations.

The new theory, advanced by the pair, identifies how objects known as “sterile neutrinos” could be the likely source of dark matter. It also demonstrates how these smaller than atom-sized particles could be central in understanding other previously unexplained astronomical puzzles, including ones related to “pulsars,” which are remains of ancient, massive stars which exploded long ago.

“The consensus of several indirect pieces of evidence leads one to believe that the long sought-after dark-matter particle is, indeed, sterile neutrino,” Biermann says.

Dark matter is material that has never been seen, but scientists say they know it exists, in part because they see the influence of invisible materials in gravity, including within the motions of astronomical objects. Up to 90 percent of the universe’s matter can’t be seen, scientists say, except through its gravitational pull.

Neutrinos are electrically neutral, sub-atomic particles, which pass effortlessly through all matter. It’s been estimated that trillions of the tiny, invisible objects pass through the human body every second. Although their existence has been theorized for half a century, physicists only recently showed these particles have mass.

The neutrinos that Biermann and Kusenko point to are referred to as “sterile” because they interact very little with one another or with the more typical neutrinos, Biermann says.

A key observation made by Biermann and Kusenko is the same neutrinos responsible for “pulsar kicks,” the force that propels these neutron stars through space at high speeds, can also explain the “reionization” of the universe.

“The idea is that in creation of the pulsar, neutrinos are emitted asymmetrically, so that they act more like a rocket engine,” Kusenko said. Reionization refers to the second of two phase changes of hydrogen gas in the early universe. The decay of sterile neutrinos could have sped up the formation of molecular hydrogen and lit up the universe’s first stars, he said.

The two scientists are among the participants scheduled for an international conference to be held at Crans Montana, Switzerland, March 25-29. Biermann recently lectured in New Mexico and plans on returning to present at the Neutrino 2006 international conference in June in Santa Fe.

Scientists are involved in international discussions of telescopic observational methods which could further back-up the premise detailed in the academic journal article. One method is through very deep X-ray observations of portions of the universe, as the decay of sterile neutrinos gives off a detectable X-ray emission, Biermann said.

The general notion that neutrinos might play a role in dark matter is an old theory but previous attempts to show how this was possible have later proved incorrect, Biermann said.

“All versions of such theories failed in a substantial way, and each time, and our proposal seems to be the first that actually points out why this approach actually can win,” Biermann said.

UA’s department of physics and astronomy is part of the College of Arts and Sciences, the University’s largest division and the largest public liberal arts college in Alabama with 355 faculty and 6,600 students. Students from the College have won numerous national awards including Rhodes Scholarships, Goldwater Scholarships, and memberships on the USA Today All-USA College Academic Team.