Milestones, People

World-renowned astronomer Donald C. Backer dies at age 66

Don Backer, a professor at UC Berkeley’s Department of Astronomy, and a world leader in the field of radio astronomy, died on Sunday, July 25. He was 66.

head shot of Don Backer with green board behind and chalked equations

Donald Backer, a UC Berkeley astronomer and discoverer of the first millisecond pulsar, died in 2010.

Don Backer, a professor in the Department of Astronomy at the University of California, Berkeley, and a world leader in the field of radio astronomy, died on Sunday, July 25, after collapsing outside his home. He was 66.

Backer joined the UC Berkeley Astronomy Department in 1975; since 1989, he held a position both as a full professor in astronomy and as a researcher in the department’s Radio Astronomy Laboratory (RAL). He served as chair of the department from 1998-1999 and from 2002-2008, and as the RAL director from 2008 until his death.

An innovative and visionary scientist, instrumentalist and observer, Backer worked in many areas of astronomy and was involved in numerous ground-breaking projects over his 40-year career. His research focused on pulsars, high-energy astrophysics, the epoch of reionization and the exploration of these topics with the most imaginative and state-of-the art instrumentation.

Equally an expert in radio astronomy techniques and engineering instrumentation, Backer insisted that his work be considered within the main body of astronomy research, and not just as radio astronomy.

“His work was characterized by a clear vision of fundamental physics, technical expertise and a passionate enthusiasm,” said UC Berkeley professor Carl Heiles, a longtime colleague of Backer’s.

Backer made seminal contributions to the study of pulsars. In the early 1980s, he and several collaborators discovered the first millisecond pulsar, a neutron star spinning close to its breakup speed. He also developed an important use for the millisecond pulsar as a probe of the gravitational wave background. Dozens of researchers around the world are in active pursuit of the discovery, characterization and use of millisecond pulsars, especially for detection of gravitational waves. Backer invented and developed digital systems for the detection and precise measurement of pulsars, and they have been adopted as standards in the field and are used at the major observatories worldwide.

Backer was a pioneer in Very Long Baseline Interferometry (VLBI), a technique of linking together distant radio telescopes to produce high-resolution images, allowing the investigation of astronomical structures with microarcsecond angular resolution. He linked the RAL’s 85-foot-centimeter wave telescope to a number of similar antennas distributed across the country and the world. He pursued ever-increasing resolution with the goal of imaging the environment of the black hole at the center of the Milky Way Galaxy. Researchers working in this area with Backer made the highest resolution image ever of a black hole. Backer led the VLBI consortium for several years, helping to develop both accurate radio astronomy and the study of plate motions in the earth’s surface.

In the past few years, Backer initiated a unique “telescope” that consists of an array of antennas spread over pastureland to detect, via their effect on intergalactic hydrogen, the first stars and galaxies that formed in the universe. This “Precision Array To Probe the Epoch of Reionization” (PAPER) led to deployment of these telescopes in Green Bank, W. Va., and in South Africa.

“Despite starting on a small scale and fabricating all of the equipment from scratch, this project is now recognized internationally as an important step toward understanding the history of the universe,” said Heiles.

As RAL director, Backer was deeply engaged in the laboratory’s two major facilities, the Allen Telescope Array (ATA) and the Combined Array for Millimeter Astronomy (CARMA). Fostering the growth of three unique radio telescopes — ATA and CARMA, as well as PAPER — he was leading efforts to cover a factor of 1000 in wavelength range, promising a bright future for the lab and the field of radio astronomy. Continuing Backer’s legacy, the lab will continue to move forward along this path of pioneering novel techniques, said Imke de Pater, professor and chair of UC Berkeley’s Astronomy Department.

Born in Plainfield, N.J., on Nov. 9, 1943, and raised in New Jersey, Backer went off to study at Cornell University, where he graduated with a B.S. in engineering physics in 1966. He then attended the University of Manchester, where he completed an M.Sc. in radio astronomy in 1968 before returning to Cornell for further graduate studies. He received his Ph.D. from Cornell in 1971.

His early career was ignited by the discovery of pulsars and the construction by Cornell of the world’s largest radio telescope, the Arecibo dish in Puerto Rico.

Among other honors during his long career, Backer was chosen for the prestigious Jansky Lectureship at the National Radio Astronomy Observatory in 2003. In addition, he served on countless national and international committees in astronomy.

At UC Berkeley, Backer’s colleagues and former students said he will be remembered not only for his valuable research accomplishments, but also for his relentless energy, deep passion for science, and as someone who cared greatly for the people around him.

‘Innately curious’

“Don was constantly challenging himself and his students, switching fields dramatically throughout his career, from pulsars to gravity waves, to the galactic center, and then to the origin of structure in the universe,” said Dan Werthimer, a former student of Backer’s who is chief scientist of SETI@home at UC Berkeley’s Space Sciences Laboratory. “Don made pioneering contributions to each of these fields, but he didn’t let it go to his head, and he always maintained his characteristic kind and gentle manner.”

“I don’t think I’ve met a finer man or a scientist that surpasses him in thoughtfulness,” said UC Berkeley astronomy professor Leo Blitz, who knew Backer since they were freshmen at Cornell 48 years ago.

Backer was determined to “pass the torch to the next generation” and trained his replacements in the field of astronomy every day, added colleague Geoffrey Bower, UC Berkeley assistant professor of astronomy and one of Backer’s former Ph.D. students. “That’s why we have some chance of moving ahead without him.”

Backer’s family remembers him fondly as someone who took great joy in travel, the simple and complex aspects of nature, hiking, swimming, skiing, going to the beach and camping.

“He was innately curious, loved to explore the earth as much as he did the cosmos, and had wonderful opportunities throughout his life to do both, close to home and around the world,” said his son, David Backer. “Every trip, personal and professional, was another chance, not to be missed, for adventure, discovery and appreciation.

“And lucky for us, he was unflappable, capable and dependable on these quests, always prepared to start a fire with only a couple of sticks, to siphon gas with a small tube, to carry someone injured on his back to get medical assistance. We and everyone who knew him will miss his spirit, integrity and bedrock.”

In addition to his wife, Susan Backer of Berkeley, Backer is survived by his son, David of Rockville, Maryland: his mother, Lura Backer of Bredenton, Fla., and a niece, a nephew and a granddaughter. His father, Phillip Backer, died in 1998 and his brother, Ken Backer, in 2007.

In lieu of flowers, donations can be sent to the Donald Backer Memorial Fund, to continue his legacy and to support the new frontiers of astronomy research and education. Checks can be made out to the UC Berkeley Foundation and mailed to Barbara Hoversten, Astronomy Department, MC3411, University of California, Berkeley, CA 94720-7450.

A private memorial service is scheduled.