The Parker Solar Probe is scheduled to launch during a 20-day window that opens July 31, 2018. During the course of 24 orbits, the spacecraft will fly by Venus seven times to gravitationally reduce its distance from the sun. Three of the spacecraft’s orbits will bring it within 3.9 million miles of the sun’s surface—approximately seven times closer than any other probe. The solar probe, which the Applied Physics Laboratory is building, will endure a solar intensity more than 500 times greater than that of an Earth-orbiting spacecraft.
“The solar probe is going to a region of space that has never been explored before. It’s very exciting that we’ll finally get a look,” said Parker, who was on the UChicago faculty from 1955 to 1995. “One would like to have some more detailed measurements of what’s going on in the solar wind. I’m sure that there will be some surprises. There always are.”
The rare honor Parker is receiving, in having a space mission named after him, continues a tradition of leadership in astronomy and physics at UChicago. It includes the Hubble Space Telescope, named after UChicago alumnus Edwin Hubble; the Chandra X-ray Observatory named after Nobel laureate Subrahmanyan Chandrasekhar, a UChicago professor who worked with Parker; the Fermi Gamma-Ray Telescope, which honors Enrico Fermi, a Nobel laureate and UChicago professor; and the Compton Gamma Ray Observatory named after Nobel laureate Arthur Holly Compton, a UChicago professor.
“The naming of the solar probe is a fitting honor for Gene Parker. His pioneering work has become a cornerstone in the field of astrophysics and exemplifies the University of Chicago’s commitment to rigorous inquiry and a challenging of conventional wisdom that produces new and exciting discovers across the sciences,” said Edward “Rocky” Kolb, dean of the Division of the Physical Sciences at UChicago and the Arthur Holly Compton Distinguished Service Professor in the Astronomy and Astrophysics.
‘Nothing mysterious about it’
Parker explains that although he first predicted the solar wind in 1957, “it wasn’t so much a prediction as a recognition that it was there.”
Parker’s early work laid the groundwork for his landmark discovery. He was a research associate beginning in 1953 at the University of Utah under Walter Elsasser, who pioneered the dynamo theory of the origin of Earth’s magnetic field. In 1955, John Simpson, a veteran of the Manhattan Project, recruited Parker to UChicago to study cosmic rays.
At that time scientists knew, based on the work of Peter Biermann and Cuno Hoffmeister, that the gaseous tails of comets, which always point away from the sun, are swept away by some form of solar particle emission. Scientists thought of these solar emission particles as being shot from the sun—much like cannon balls from cannons. Parker, however, came to see the process as a flow of gas that is subject to the simple laws of hydrodynamics, becoming what he called the solar wind.
The first paper that Parker submitted to the Astrophysical Journal proposing the solar wind was panned by two eminent reviewers. Parker pointed out to Chandrasekhar, who was the journal’s editor at the time, that neither reviewer had flagged any mathematical flaws in the work, and the paper was published in 1958.
“Chandra told me many years later that he was very skeptical about it, but since he couldn’t find anything wrong with the math, he figured it was worth thinking about,” Parker said.
The results were verified in 1962 with data collected by the Mariner II space probe to Venus, the first successful interplanetary mission. Understanding solar wind made it possible to expound the causes of magnetic storms, auroras and other solar-terrestrial phenomena.