Bryn Mawr College

Visiting Assistant Professor of Physics

I was an undergraduate at Caltech (BS in physics, 1987) and went to graduate school at Princeton (MA and PhD in physics, 1989 and 1992). I spent three years as Jansky Fellow of the National Radio Astronomy Observatory in Charlottesville, Virginia. While in Charlottesville, I also briefly taught at the University of Virginia. I returned to Princeton, first as a postdoc and then as a faculty member, before moving to Bryn Mawr College.

My research focuses on observations of pulsars—rapidly rotating neutron stars, which emit lighthouse-like beams of radio waves. As a pulsar rotates, its beam sweeps by the Earth; we can detect a pulse of radio waves at each rotation. I observe pulsars using large radio telescopes such as those in Arecibo, Puerto Rico and Green Bank, West Virginia.

Some of the most exciting pulsar work comes from millisecond pulsars, neutron stars which rotate hundreds of times a second (and hence have rotation periods of milliseconds.) Imagine a star a bit more massive than our sun, rotating as fast as a kitchen blender. That's what a pulsar is like. Unbelievable, but true.

By observing ("timing") the pulses from any given pulsar, we are able to monitor the behavior of a pulsar over days, months, and years. We can detect subtle losses of energy in the pulsar. We can detect its motion through the sky with milliarcsecond precision. Some pulsars are in binary systems with other stars (or planets), and we can detect the motion of the pulsar in their orbits.

Some of the most exciting work involves binary pulsar systems. Because pulsar timing is an exquisitely precise technique—we can measure pulses from some pulsars with precision much better than one microsecond— we can observe subtle phenomena in pulsar orbits which arise because of general relativistic effects in their orbits. They have proven a fertile ground for using and testing Einstein's theory of relativity.

Among other things, I have been using pulsars to constrain neutron star masses, to test theories of gravity, to study the evolution of eclipsing pulsar binaries, to indirectly detect gravitational radiation via its effect on the kinematics of binary stars, and, in the future, to directly detect nanoHertz (10-year-time-scale) gravitational radiation.

E-mail:  dnice@brynmawr.edu
Office:  Park Science Center, Room 351
Telephone:  +1-610-526-5361
Fax:  +1-610-526-7469

My office hours are listed on my course webpages (see below).