Astrophysicist gets $1 million grant to hunt for dark matter

Christopher Stubbs, center, works with Peter Doherty, left, a research engineer, and graduate student Alan Diercks, right.

UW astrophysicist Christopher Stubbs has been awarded a $1 million grant from the James S. McDonnell Foundation to intensify his six-year search for dark matter in the universe.

Stubbs, a professor in both astronomy and physics, is one of 10 early-career scientists worldwide who will receive the one-time Centennial Fellowship grants from the St. Louis-based foundation. The institution, which supports scientific, educational and charitable causes, was created in 1950 by James S. McDonnell Jr., founder of McDonnell Douglas Corp., now part of The Boeing Co.

Another of the grants was awarded to Leonid Kruglyak, a statistical geneticist at the Fred Hutchinson Cancer Research Center in Seattle and a UW affiliate associate professor in both genetics and molecular biotechnology. Kruglyak will use his grant to support experimental pilot projects.

Physicists have long puzzled over the problem of the dark, or “missing,” matter in the universe. They know how much matter there should be, but the mass has not been accounted for in observations. It could be accounted for by massive but unseen bodies in space, by as-yet-unknown properties of subatomic particles or a combination of the two.

Stubbs leads a group looking for dark matter in the form of astrophysical objects, particularly massive bodies on the scale of Jupiter or larger, that cannot be observed directly.

“If our galaxy was filled with Jupiters, it would be very, very hard to see them because they don’t emit any light,” he said.

Instead, these objects can be detected by their gravitational effect on light emitted from stellar objects farther away. That effect, called gravitational lensing, makes the bright object appear to be even brighter as its light waves, on their way to Earth, pass near a dark object and are bent by its gravity.

It is not uncommon to see gravitational lensing when looking toward the center of the Milky Way, but because of the density of objects at the heart of the galaxy it is impossible to determine for sure whether the light is being bent by dark objects or bright ones. So Stubbs’ group has looked away from the center of the galaxy, through its dark halo, for evidence of gravitational lensing. But in six years of the MACHO Project — for Massive Compact Halo Object — only 17 such occurrences have been documented.

With the McDonnell grant, Stubbs plans to build a highly sensitive digital camera with a wide field of view, which will detect 10 times more events per year than his team has observed so far. The camera will be attached to the 2.5-meter Las Campanas telescope in Chile.

“I think we will be able to determine conclusively whether the signal we see is dark matter or not,” he said. If it is, that knowledge will lead to further study in several areas. But if the signal is not dark matter, it likely means the answer to the dark matter problem lies in particle physics rather than astrophysics.

“Either way, science benefits,” Stubbs said.

“What this grant does is it turns the corner on this project. I’m now convinced that this project will go forward. This contribution is absolutely pivotal for us to accomplish what we want to.” ¶

Vince Stricherz, News and Information