Last summer, NASA’s Parker Solar Probe split the predawn skies in a blaze of light as it headed closer to the sun than any other spacecraft. Named for pioneering University of Chicago astrophysicist Eugene Parker, the probe has now made three of its 24 planned passes through the sun’s corona—enough for scientists to announce their first discoveries.
In four papers published Dec. 4 in Nature, researchers describe strange space phenomena and a flood of new data that will help us understand everything from the nature of stars to improving our forecasting of solar storms that can affect electronics on Earth.
Sidling up to the nearest star that humans can reach, the Parker Solar Probe learned new information about two types of major space weather events. It also saw the first signs of the zone around the sun where cosmic dust disappears—predicted decades ago, but never seen—as well as an entirely new phenomenon: bizarre “switchbacks” in the solar wind that flows off the surface of the sun. Scientists said it will dramatically change our theories of the corona and solar wind.
Scientists are eager to learn more about the the solar wind—a flow of charged particles off the surface of the sun which radically affects the Earth and the entire solar system, which University of Chicago Professor Emeritus Eugene Parker first proposed in 1958. NASA named the solar mission after the famed astrophysicist in 2017.
Parker, now 92, is poring over the probe's early results with interest.
"Now that the data is finally coming in and being analyzed, things are getting really exciting,” he said. “We’ve already seen evidence for some very surprising phenomena—which you should always expect when you travel into regions where spacecraft have never been before. That is part of the excitement of these missions, and I’m looking forward to what comes next.”
“It is appropriate that a spacecraft named in honor of our colleague Eugene Parker, who made contributions across nearly all of heliophysics, should have findings that are so immediately diverse and interesting,” said Angela Olinto, dean of the Division of the Physical Sciences and the Albert A. Michelson Distinguished Service Professor in the Department of Astronomy and Astrophysics. “These findings represent an incredible opportunity to help us unravel the many mysteries that stars still hold.”
Though it may seem placid to us here on Earth, the sun is anything but quiet. Our star is magnetically active, unleashing powerful bursts of light, particles moving near the speed of light and billions of tons’ worth of material.
What happens on the sun is critical to understanding how it shapes the space around us. Most of the material that escapes it is part of the solar wind, a continual outflow of ionized gas, called plasma. This plasma carries with it the sun's magnetic field, stretching it out through the solar system in a giant bubble that spans more than 10 billion miles.
A simulation of “switchbacks,” reversals in the direction of the magnetic field embedded in the solar wind.
Closer to the solar wind’s source, Parker Solar Probe saw a much different picture from the one we have on Earth: a complicated, active system. One event in particular drew the eye of the science teams: flips in the direction of the magnetic field, which flows out from the sun, embedded in the solar wind. These reversals, dubbed “switchbacks,” last anywhere from a few seconds to several minutes as they flow over Parker Solar Probe. During a switchback, the magnetic field whips back on itself until it is pointed almost directly back at the sun.
“Waves have been seen in the solar wind from the start of the space age, and we assumed that closer to the sun the waves would get stronger, but we were not expecting to see them organize into these coherent structured velocity spikes,” said Prof. Justin Kasper, AB’99, of the University of Michigan, a UChicago alum whose team helped build one of the instruments aboard the probe. “We are detecting remnants of structures from the Sun being hurled into space and violently changing the organization of the flows and magnetic field. This will dramatically change our theories for how the corona and solar wind are being heated."