Donald C. Backer (born November 9, 1943) is an American astrophysicist best known for his work on pulsars, particularly his role in the discovery of PSR B1937+21, the first millisecond pulsar.
Backer was born in Plainfield, New Jersey. He received a Bachelor of Science degree in engineering physics from Cornell University in 1966, followed by a Master of Science degree in radio astronomy from Manchester University in 1968, and then returned to Cornell to earn his doctorate in astronomy in 1971. Backer then took post-doctoral positions first at NRAO in Charlottesville, Virginia, and then at NASA/GSFC in Greenbelt, Maryland. In 1975, Backer moved to the University of California, Berkeley as a research astronomer in the Radio Astronomy Laboratory, and became professor of astronomy at Berkeley in 1989.
Backer has done a lot of work in the field of pulsars. Aside from the first millisecond pulsar, PSR B1937+21, Backer was also involved in the discovery of a Jupiter-sized planet around PSR B1620-26, thought to be the oldest known extrasolar planet. Related to his work on pulsars, Backer has worked with the Pulsar Timing Array to try to detect gravitational waves from rapidly rotating neutron stars, and to try to set limits on the gravitational wave background of the universe. More recently, he has also been working on studying the epoch of reionization, leading a collaboration between the University of California, Berkeley, the University of Virginia, the University of Pennsylvania, and NRAO called the Precision Array to Probe the Epoch of Reionization (PAPER).