NASA mission honors pioneering UChicago physicist

Prof. Eugene Parker was 31 years old in 1958 when he proposed a radical idea that changed the way we think about the sun and solar system. The space between planets was not empty, he said, but filled with a “solar wind”: an expanding force of particles flowing off the sun out through the farthest reaches of the solar system.

Like other scientists with outlandish theories about the sun before him, he was not believed at first.

“The first reviewer on the paper said, ‘Well I would suggest that Parker go to the library and read up on the subject before he tries to write a paper about it. Because this is utter nonsense,’” Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus in Physics at the University of Chicago, recalled with a laugh.

More than half a century later, in honor of his work, which opened a new field of astrophysics, Parker is the first living person to have a NASA spacecraft named after him.

On the morning of Aug. 12, he was at Cape Canaveral to witness the launch of the Parker Solar Probe, which will fly closer to the sun than any mission.

The launch lit up the muggy night, where three generations of Parker family members watched from NASA’s viewing terrace. Cheers erupted during takeoff, and after officials announced the spacecraft was safely on its way, the company hugged, shook hands and took celebratory sips of Parker Solar Pale Ale, brewed especially by Chicago-area company Crystal Lake Brewing.

“All I can say is wow, here we go,” said Parker, the S. Chandrasekhar Distinguished Service Professor Emeritus in Physics at UChicago. “[Now I] really have to turn from biting my nails … to thinking about all the interesting things which I don’t know yet. We’re in for some learning the next several years.”

The probe will investigate the mysterious workings of the sun and the solar wind that Parker proposed decades ago.

“Eugene Parker had a vision of the solar system that was way ahead of its time,” said Prof. Angela Olinto, dean of the physical sciences at UChicago. “His work basically laid the foundation of a whole new field, and he serves as an inspiration to all of us here at the University of Chicago who are working to expand the boundaries of human knowledge.”

A far-out idea

Parker was a young UChicago assistant professor when he began looking into an open question in astrophysics at the time: whether there were particles coming off the sun. It seemed unlikely, since Earth’s atmosphere doesn’t flow out into space, and presumably the same would be true for the sun. But scientists had noticed an odd phenomenon: The tails of comets, no matter which direction they traveled, always pointed away from the sun—almost as though something was blowing them away.

Parker sat down and began to do the math. He calculated that if the sun’s corona was a million degrees, there had to be a flow of particles expanding away from its surface, eventually becoming extremely fast—faster than the speed of sound. The idea was unheard of at the time, but that’s what the physics was telling Parker.

“And that’s the end of the story, except it isn’t, because people immediately said, ‘I don’t believe it,’” Parker said.

He wrote a paper and submitted it to the Astrophysical Journal; the response from scientific reviewers was swift and scathing.

“You must understand how unbelievable this sounded, when he proposed it,” said Fausto Cattaneo, UChicago professor of astronomy and astrophysics. “That this wind not only exists, but is traveling at supersonic speed! It is extraordinarily difficult to accelerate anything to supersonic speeds in the laboratory, and there is no means of propulsion.”

Luckily, the editor of the journal at the time was eminent astrophysicist Subrahmanyan Chandrasekhar, Parker’s colleague at the University of Chicago. Chandrasekhar didn’t like the idea either, but the future Nobel laureate couldn’t find anything wrong with the math, so he overruled the reviewers and published the paper.

And there it sat until 1962, when a NASA spacecraft to Venus called Mariner II took readings on its journey. The results were unambiguous. “There was the solar wind, blowing 24/7,” Parker said.

Mission to the sun

The discovery reshaped our picture of space and the solar system. Scientists came to understand that this wind not only flows past Earth, but throughout the solar system and beyond. It also both protects and threatens us.

“The solar wind magnetically blankets the solar system, protecting life on Earth from even higher-energy particles coming from elsewhere in the galaxy,” Olinto said. “But it also affects the sophisticated satellite communications we have today. So understanding the precise structure and dynamics and evolution of the solar wind is crucial for civilization as a whole.”

Thus scientists have been eager for a mission to the sun since space travel first became possible. But the extreme temperatures meant they needed to wait until the development of technology that could shield the spacecraft from the intense heat and radiation of the sun. The Parker Solar Probe’s heat shield, made of just under five inches of a cutting-edge carbon composite, will keep the craft’s delicate instruments at a gentle 85 degrees Fahrenheit even as the corona rages at 3 million degrees Fahrenheit outside.

It will need it, because when the spacecraft launches in August, it will begin a seven-year journey to the blisteringly hot corona, visible as the halo around the sun during an eclipse. It will be by far the closest we’ve ever come to a star, and scientists are itching to get a look at the physics close-up.

Two of the most pressing questions for this mission, which date back to Parker’s earliest work: Why is the corona so much hotter than the surface of the sun? How does the solar wind accelerate away from the sun?

A deeper understanding of these processes will help forecast space weather that affects life here on Earth, understand the conditions that astronauts in orbit above our world and journeying for long distances would face, and even provide clues about what kinds of star activity might favor habitability on distant planets.

Parker is looking forward to the data.

“You’re exploring unknown territory, and you can be darn sure there are some surprises waiting for us there,” he said. “Things are never quite what you thought they were.”

‘Gene Parker is like God’

Over his career, Parker went on to study other phenomena, such as cosmic rays and the magnetic fields of galaxies. His name is littered across the field of astrophysics: the Parker Instability, which describes magnetic fields in galaxies; the Parker equation, which describes particles moving through plasmas; the Sweet-Parker model of magnetic fields in plasmas, the Parker limit on the flux of magnetic monopoles.

“In our field, Gene Parker is like God,” said Cattaneo. “Most people would have one good idea and rest on that. This guy had God knows how many. There are not many people like him.”

In announcing the new name of the mission at the University last year, NASA said that given Parker’s accomplishments within the field and how closely aligned this mission is with his research, the decision was made to honor him prior to launch in order to draw attention to his important contributions to heliophysics and space science.

“We’re very proud to be able to carry Gene’s name with us on this amazing voyage of discovery,” said Nicola Fox, Parker Solar Probe project scientist, of the Johns Hopkins University Applied Physics Laboratory.

Asked for advice for those early in their careers, Parker said, “I have never made a significant proposal, but what there was a crowd who said ‘Ain’t so, can’t possibly be.’ If you do something new or innovative, expect trouble. But think critically about it because if you’re wrong, you want to be the first one to know that.”

“I’ve been delighted to be alive in this period of time because of all the wonderful things that have been happening,” said Parker, who retired from the University in 1995. “I’m just happy to be born at the right time.”