The Search For Dark Matter – With Guest Dr. Matthew Walker (Part 2)

March 11, 2013

John P. Millis, PhD for – Your Universe Online

One of the defining characteristics of dark matter is that it does not interact with light. But these electromagnetic interactions are how we traditionally conduct astronomical research – which begs the question, how do we search for dark matter?

It turns out that the search for dark matter is actually a study on how dark matter interacts with its surroundings. But another problem quickly arises. It turns out that the interactions that we would expect depend on what dark matter actually is – or, more specifically, on whether dark matter is hot, warm or cold.

Each of these types of potential dark matter would have its own set of characteristics and therefore lead to different sets of predictions about what we would expect to see out in the cosmos.  So, which kind of dark matter fits best with what we observe when we gaze into space with our most advanced astronomical equipment?

To explore these questions we spoke once again with Dr. Matt Walker, a research scientist at the Smithsonian Center for Astrophysics at Harvard University. In this episode on our series of dark matter we also discuss the specific methods that we use to find dark matter, both directly and indirectly. Finally, we talk about the recent results from the Fermi Gamma-ray Telescope. Could we be seeing the first evidence of dark matter at the center of our Galaxy?

Listen to parts one and three of the interview, “What Is Dark Matter?” and “The Future Of Dark Matter Research.”


Dr. Matthew Walker is an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, and studies dark matter by measuring the motions of stars in galaxies. He has measured velocities for thousands of stars within the dwarf galaxies that orbit the Milky Way, and uses these data to infer the small-scale clustering properties of dark matter.

Dr. Walker earned a BS in physics and a BA in philosophy from Western Illinois University in 1999, and a PhD from the University of Michigan in 2007. He was a postdoctoral fellow at the Institute of Astronomy at the University of Cambridge, England, and is currently a Hubble postdoctoral fellow at Harvard College Observatory.