World-renowned supernova expert honored for breakthrough contributions to astronomy

Mark Phillips received the UCSC Alumni Achievement Award

Mark Phillips (Ph.D. ’77, astronomy & astrophysics) at the Alumni Awards celebration on Oct. 27, 2023.

The Alumni Association at UC Santa Cruz is proud to present this year’s honorees of the UCSC Alumni Awards. These awards recognize and honor alumni who have demonstrated outstanding professional achievements, made distinct contributions to society, provided impactful contributions to UCSC, and who have embodied the values and spirit of the university. 

Mark Phillips received the Alumni Achievement Award on Oct. 27, 2023, for his pioneering supernova research that led to the reversal of a major scientific theory on the trajectory of the universe, and for the indelible legacy he has left for aspiring astronomers.

A comet in the southern California sky ignited in Mark Phillips (Ph.D. ’77, astronomy & astrophysics) a lifelong passion for studying the cosmos and inspired a brilliant career as a world-renowned astronomer. 

With a mathematical mind and habitual curiosity, Phillips was destined for a megastar career behind a telescope. His interest in the galaxies was sparked when his father woke him in the middle of the night to witness a comet in the San Diego sky when he was in junior high school. A science unit on constellations, an amateur astronomy magazine, and tutoring sessions to help his sister through an astronomy course in college fueled his decision to study astronomy and math at San Diego State and to pursue a Ph.D. in astronomy and astrophysics at UC Santa Cruz. 

UCSC professor instilled his love of research

While pursuing his Ph.D. at UCSC, Phillips worked as a research assistant for Dr. Don Osterbrock, who became an important mentor for Phillips, both personally and professionally. 

“He had a tremendous impact on my career,” said Phillips. “He was a second father to me. He instilled in me the love of research, and bird watching!”

Osterbrock, an avid birder, invited Phillips to go birding soon after he arrived on campus. Phillips found that he not only enjoyed having an eye on the night sky, but he also enjoyed searching for birds during the day. This shaped his lifelong interest in photographing birds, which he enjoys near his home in La Serena, Chile. 

The mountains drew him to Chile; the night sky kept him there

A California native, Phillips did not anticipate spending 44 years of his life in Chile. It was his love for hiking that first drew him to the South American country that boasts endless mountain ranges. 

“A scientist from the Cerro Tololo Interamerican Observatory (CITO) came to campus to recruit young astronomers,” said Phillips. “I liked to hike, and I knew Chile was famous for mountains, so I was intrigued.”

Phillips and his roommate, Steve Hawley (Ph.D. ’77, astronomy & astrophysics), ventured to Chile together. Their shared experience launched careers in which they would become pioneers in their field–Phillips on the ground and Hawley in the sky. Hawley, who became a NASA astronaut, received the 1985-86 UCSC Alumni Achievement Award.

Phillips acclimated well to South America. He mastered conversational Spanish–impressing Silvanna, a native Chilean, whom he married–and after postdoctoral work in Australia, he returned to a staff position at CITO. During his 18-year tenure he made a revolutionary discovery. 

Pioneering formula was impetus to scientific breakthrough

After more than a decade of research on powerful energy sources in the nuclei of galaxies—a continuation of the work on which he and Osterbrock collaborated at UCSC—Phillips turned his attention to supernovae (exploding stars), and specifically, Type Ia supernovae. There was one significant hurdle: supernovae can only be seen in the Milky Way Galaxy about every 100 years. 

“We found a telescope that could help us discover Type Ia supernovae in tens of other galaxies, giving us an enormous amount of data,” said Phillips.  

He began measuring the light patterns with time of Type Ia supernovae with never-before-used methods. He published his new formula on how to precisely measure cosmic distances—referred to as the Phillips Relationship—in a seminal paper in 1993. It was a breakthrough that fueled excitement within the cosmology community and opened new opportunities that would have astronomical scientific impacts.

A trip back in time uncovered a key to the future

“After that study was released, it was game on,” said Phillips, who with colleagues from Chile formed the Calán/Tololo Supernova Survey. The team used the brightness of the Type Ia supernova to produce precise calibrations and measurements of the Hubble Constant, which provides information on the rate of expansion and the age of the universe. 

Phillips then joined a group of 20 astronomers in forming the High-Z Supernova Search team, which measured the light of distant supernovae that exploded billions of years ago. According to Phillips, this work enabled them to essentially look back in time to gain a better understanding of how the universe has evolved with time. 

“We went further back in time to search for supernovae when they were much further away, and measured the expansion rate as a function time, looking backwards,” said Phillips.

And that is when a major scientific discovery with philosophical implications was discovered.

A decades-long theory gets reversed

“We had always thought that after the Big Bang, the expansion of the universe would slow down with time due to the force of gravity,” said Phillips. “But what we found was that it was actually expanding and accelerating. It was totally unexpected and a complete reversal of the theory that astronomers had held for decades.”

These shocking new findings by the High-Z Supernova Search team, along with those published by an independent research team at Lawrence Berkeley Laboratory, led to the idea that a mysterious Dark Energy is acting against gravity to accelerate the expansion of the universe. For their extraordinary discovery, both teams were honored with the Nobel Prize for Physics in 2011.

For his part, Phillips and the High-Z Supernova Search team all shared in the 2007 Gruber Cosmology Prize, widely acknowledged in the field of cosmology as second only to the Nobel Prize. The team also was honored with the 2015 Breakthrough Prize for Fundamental Physics. 

What’s next? 

Though recently retired, the light on his illustrious career is still flickering as Phillips wraps up a paper on decades-long research he began at Carnegie’s Las Campanas Observatory, where he served for 14 years.  

Phillips spent his entire career in observatories exploring stars that exploded millions of years ago in galaxies far away to help shed light on the future of our own universe. And like the constellations that were his North star, his legacy work will guide and inspire the next generation of astronomers curious to unlock the mysteries that lie beyond them.