Stuart Bowyer, pioneer of EUV astronomy and SETI, dies at 86

Stuart Bowyer, an astronomer who convinced NASA to launch the first satellite to study the heavens in extreme ultraviolet wavelengths and started one of the longest running searches for extraterrestrial intelligence (SETI) in the world, died Sept. 23 at a hospital near his home in Orinda, California. His family said the cause was complications associated with COVID-19.

Bowyer, a professor emeritus of astronomy at the University of California, Berkeley, was 86.

Charles Stuart Bowyer, or Stu, as he was known to friends and foes, was brash and bold, enthusiastic and pushy, hard-working and fun-loving. While he himself admitted that he wasn’t necessarily the best mind in the room, he was astute enough to choose the best people to work with.

“This may be his greatest scientific achievement — attracting very good graduate students and postdocs and helping them develop into world leaders,” said Bowyer’s longtime friend and colleague Forrest Mozer, professor emeritus of physics at UC Berkeley. “During this time, he had a group of graduate students who have since grown into leaders in many subfields of astrophysics. Stuart realized this; he once told me that he was not so smart, but he was smart enough to have a team of great scientists.”

“Stuart Bowyer was a larger-than-life character. He did nothing by halves. People who knew him, it seemed, either loved him or hated him, but no one I ever met was neutral about Stu,” said former UC Berkeley postdoctoral fellow Jean Brodie, now director of the Centre for Astrophysics and Supercomputing and a distinguished professor at Swinburne University in Melbourne, Australia. “Nonetheless, beneath the bombastic veneer was a serious scientist with a dedication to his students and postdocs, the equal of which I have never encountered, before or since.”

While Bowyer was trained and made some of his first contributions to the field of X-ray astronomy, he is best known for championing observations in a wavelength band that had not yet been explored: extreme ultraviolet (EUV), a band between ultraviolet and X-ray. EUV radiation should be emitted by hot objects — for example, the atmospheres of stars — and could potentially tell astronomers about the evolution of stars and the composition of the interstellar medium.

When he first proposed a space-based EUV experiment to NASA, however, the idea was pooh-poohed by other astronomers. Most thought that he’d see nothing, because EUV is absorbed by gas in the interstellar medium. EUV is absorbed by gases in our atmosphere, too, preventing such observations from Earth.

But Bowyer persisted, demonstrating in 1975 that detectors his team built and placed aboard the joint U.S.-Soviet Apollo-Soyuz manned space mission could see EUV from other stars, including hot white dwarfs and a nova. His team confirmed these findings with subsequent sky surveys by instruments placed aboard balloons and sounding rockets, which rise above most of the atmosphere that blocks the wavelength band.

Stuart Bowyer and Roger Malina with model of EUVE satellite

Roger Malina and Stuart Bowyer pose next to a prototype of the EUVE telescope at the Space Sciences Laboratory. EUVE was launched in June 1992 and operated for nine productive years. (UC Berkeley photo by Jane Scherr)

NASA finally approved the Extreme Ultraviolet Explorer (EUVE) mission in the early 1980s, the first one dedicated to EUV astronomy, with Bowyer as principle investigator (PI). According to Mozer, Bowyer was one of the first, if not the very first, scientist to become PI of an entire NASA mission.

After many years of development at UC Berkeley’s Space Sciences Laboratory and Bowyer’s Center for Extreme Ultraviolet Astrophysics, the EUVE was launched into Earth’s orbit on June 7, 1992. It survived for nine years, cataloging about 800 EUV sources in the Milky Way galaxy, before losing operating funds and shutting down on Jan. 31, 2001. It burned up in the atmosphere a year later.

“Stu’s major scientific idea was that, contrary to the general opinion, one could learn about the universe by observing its extreme ultraviolet radiation,” Mozer said. “The scientific community was skeptical, because the interstellar medium was opaque at such wavelengths. But Stu persisted, was awarded the EUVE satellite program, and he showed there were enough gaps in the medium that one could see this radiation to great distances in some directions.”

Observing in the EUV today is as essential as X-ray observations when studying hot objects such as white dwarfs and stars with hot, flaring coronas, though it’s useful mostly for studying our own galaxy, because of absorption by interstellar gas. Bowyer used EUV to map the bubble of gas around our solar system and discovered unsuspected clouds of cool, EUV-emitting gas in distant galaxy clusters, including the Virgo and Coma clusters.

Search for extraterrestrial intelligence

Though Bowyer devoted most of his career to EUV and X-ray astronomy, he initiated one of the first projects to systematically search for radio signals from planets around other stars. His interest was piqued by the release in 1971 of the famed Cyclops Report, a document that proposed an international network of radio telescopes to search for intelligent life in the universe.

Bowyer with students in 1992

Stuart Bowyer with Dan Werthimer, David Ng and Chuck Donnelly in 1992 discussing their ongoing SETI project, SERENDIP. (UC Berkeley photo by Jane Scherr)

While Cyclops was never built, Bowyer’s project — dubbed SERENDIP, for Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations — started in 1977 on a single, 85-foot radio telescope at UC Berkeley’s Hat Creek Observatory in Northern California. It scanned 100 radio frequencies simultaneously and was funded primarily by private donors, including science writer Arthur C. Clarke and the Planetary Society, which at the time headed by astronomer Carl Sagan.

One of the scientists Bowyer enticed to work on the project was Jill Tarter, who went on to become director of the Center for SETI Research and was the model for the character played by Jodie Foster in the 1997 film Contact. After earning a Ph.D. from UC Berkeley’s astronomy department, she was tapped by Bowyer to program a computer — a PDP-8/S — to analyze the radio signals captured by the Hat Creek Observatory telescope.

“When Stu approached me in 1975 with a copy of the Cyclops Report and a surplus PDP-8/S that he needed to enable his visionary SETI observing project on the major telescope at UC Berkeley’s Hat Creek Radio Observatory, I was hooked,” she said. “I had both the engineering background and the current knowledge of the cosmic universe — at the right place, at the right time. When I signed up, Stu changed my professional career forever. I wish I could thank him again.”

Another graduate student, Dan Werthimer, was drawn to UC Berkeley in 1982 because of Bowyer’s SERENDIP project. Werthimer remained associated with the project his whole career, expanding SERENDIP to various telescopes and arrays, including the world’s largest radio telescope in Arecibo, Puerto Rico. He joined with others in 1999 to create SETI@home, a desktop screensaver that, until early this year, analyzed the radio data in search of interesting signals.

The SETI project Bowyer founded and later handed off to others set UC Berkeley up to become one of the centers of SETI, culminating in the establishment in 2015 of Breakthrough Listen with $100 million from Yuri Milner, an Israeli-Russian science and technology investor and philanthropist.

According to Werthimer, who currently is the Marilyn and Watson Alberts SETI Chair in UC Berkeley’s Department of Astronomy and at its Space Sciences Laboratory (SSL), Bowyer got the idea of piggybacking on radio telescopes that were doing other observations, because telescope time is expensive, and you need a lot of telescope time to conduct a powerful search for ET.

“Stu, Mike Lampton and Jack Welch developed an idea called commensal SETI,” he said. “Astronomers point the radio telescope wherever they want, and we connect our detectors and listen; we go along for the ride. We don’t really know where to look anyway, and it turns out that astronomers look in lots of interesting places, and they do sky surveys, which is what we wanted to do with SETI. With commensal SETI, we get the telescope 24 hours a day, all year round.”

Though most other SETI researchers compete for telescope time or build their own dedicated telescopes, SERENDIP has had great success piggybacking on other radio observations, though it has yet to find a signal from another civilization. While SERENDIP I monitored 100 radio frequencies, today it’s possible to monitor 100 billion frequency channels simultaneously, while vastly improved telescopes provide coverage of the sky that is another 1,000 times greater.

“Commensal observing was a powerful idea in SETI, and that started with Stu,” Werthimer said.

X-ray astronomy

Bowyer was born Aug. 2, 1934, in Toledo, Ohio, and attended grade school in a one-room school a mile from his father’s farm in Orland Park, Illinois, outside Chicago. He graduated from Orland Park High School as the valedictorian of his class and enrolled at Miami University of Ohio, from which he received a B.A. He earned a Ph.D. in physics from The Catholic University of America in 1965, with a thesis on X-ray astronomy.

Stuart Bowyer with colleagues in 1987

Kinsey Anderson, Francesco Paresce and Stuart Bowyer at the Space Sciences Laboratory. (Ed Kirwan Graphic Arts photo)

After a brief stint studying solar physics as a research physicist at the Naval Research Laboratory in Washington, D.C., he joined the Department of Space Sciences at the Catholic University of America as a research professor, initiating a program in galactic X-ray astronomy. He joined UC Berkeley’s astronomy department in 1968, where he conducted numerous sounding rocket experiments and helped build experiments for the HEAO-A spacecraft and the Spacelab-1 mission aboard the Space Shuttle Columbia.

Over his career, he trained a group of about 30 graduate students, many of whom have gone on to become leaders in the field of EUV astronomy, Mozer said. He and his team invented and/or developed many of the instruments that are the mainstays of that field today, including the grazing-incidence mirrors used to deflect EUV light into detectors, since normal mirrors do not reflect it. At its peak, Bowyer’s projects at SSL employed more than 150 engineers and scientists.

Bowyer retired in 1994, though he continued his research as the founder and director of the UC Berkeley’s Center for EUV Astrophysics, the first center outside of NASA to become responsible for operational control of a mission and its instrumentation, reduction and archiving of data from the satellite, analyzing the scientific results and managing guest investigators.

Over his career, Bowyer authored or co-authored more than 500 scientific papers, and his work is referenced in more than 10,000 publications. He received many awards and honors, including the NASA Exceptional Technical Achievement Medal, the NASA Exceptional Scientific Achievement Medal, the Alexander von Humboldt Foundation’s Humboldt Prize, an honorary doctor of science degree from Miami University of Ohio, an honorary doctor of philosophy degree from the Catholic University of America, the NASA Distinguished Public Service Medal, the Computerworld Smithsonian Award and the COSPAR Massey Award.

Bowyer is survived by his wife, Jane Baker Bowyer, a retired professor of education at Mills College in Oakland; his sons, William and Robert; his daughter, Elizabeth; and five grandchildren.