An unprecedented mission to venture close to the sun has revealed a strange region of space filled with rapidly flipping magnetic fields and rogue plasma waves.
Scientists say the findings, described in a series of reports in the journal Nature, could help explain long-standing mysteries — like why the sun's extended atmosphere is hotter than its surface.
They also could help scientists better understand and predict solar storms that might disrupt vital artificial satellites that orbit our planet.
"The sun, of course, is the source of life on Earth and the reason we can all be here. But the sun also has dangers associated with it," says David McComas, an astrophysicist at the Princeton Plasma Physics Laboratory.
The Parker Solar Probe was built to withstand searing temperatures of up to 2,500 degrees Fahrenheit. Flybys of Venus help it adjust its orbit to gradually get closer to the sun, hurtling around the star at 430,000 miles per hour.
In 2025, it will come within 4 million miles of the sun's surface, or about one-tenth the orbital distance of Mercury, according to NASA. So far the probe has swung close to the sun three times, flying around 15 million miles from its surface.
"The sun is already looking very different from what we've seen before," says Justin Kasper, an astrophysicist at the University of Michigan.
From Earth, during a total solar eclipse, it's easy to see the sun's corona, an aura of plasma that is the sun's outer atmosphere. The Parker Solar Probe is designed to plow through the corona with instruments that measure magnetic fields, plasma, and energetic particles.
All of this lets researchers explore the origin of the solar wind, charged particles that continually spew out of the sun.
It turns out that close to the sun, the wind seems to get sped up by powerful, rogue waves that move through the magnetic field, says Kasper.
"We'd see suddenly a spike in flow, where in just a couple seconds the solar wind would start flowing 300,000 miles an hour faster," he says.
"Sometimes these spikes, or stronger waves, last for a couple seconds, sometimes they last for hundreds of seconds," Kasper says. "But they nearly double the speed of the solar wind, and they are so violent that they actually flip the direction of the magnetic field in the solar wind around."
It's really pretty spectacular, says Stuart Bale, of the University of California at Berkeley.
"The wind is not just steady," Bale says. "There is a quiet, kind of steady flow, but then on top of it, we see these huge magnetic structures. The magnetic field flips around 180 degrees on a very short timescale, often, and there are jets of plasma in these structures."
These features of the solar wind were so surprising that at first researchers thought their instruments might be malfunctioning, says Nicola Fox, director of the Heliophysics Division at NASA's headquarters, who is the mission's project scientist.
It's not clear what causes these powerful waves, but they could be the reason that the sun's atmosphere is so hot, something that researchers have struggled to explain.
"This was one of the findings that I found most interesting because it addresses this really important question," says Daniel Verscharen, an astrophysicist at University College London.
He says what heats the corona has been a mystery that scientists have pondered for around 80 years. "This is definitely one of the biggest open questions that we have," Verscharen says.
"For me, to have seen something on the very first orbit, that was so surprising, it is just amazing," says Fox.
"We knew we were going into a region we've never been before. It is a voyage of discovery. It's going to the last sort of major region of our solar system to ever be visited by a spacecraft," she says. "And as we continue to get closer and closer, then I'm sure that we are going to continue to see more and more surprises."
Other observations from the probe show that the solar wind rotates around the sun much faster than the standard models of the sun had predicted. Scientists also found preliminary signs of the existence of a dust-free region around the sun, one that was first predicted back in 1929, says Fox.
The thinking has been that the sun's heat either vaporizes the dust or that pressure from sunlight pushes it away. The probe has found that dust starts to thin out about 7 million miles from the sun, and then continues to decrease steadily.
"That's another of our big science results, this proof that there is indeed a dust-free region very close to the sun," Fox says.
The next close approach to the sun will come in January, after a flyby of Venus later this month.
The mission was named after Eugene Parker, who first proposed the existence of the solar wind back in the 1950s. It's the only NASA mission named after a living person, and Parker got to see the rocket launch that carried the probe into space.
In July, Fox traveled to Chicago to share the initial results with Parker, who is now 92 years old and a revered figure in the community of scientists who study the sun.
In a written statement distributed by the University of Chicago, where he is professor emeritus, Parker said that it had been humbling to watch the probe blast off and disappear into the night sky.
"But now that data is finally coming in and being analyzed, things are getting really exciting," he said.
An earlier version of this story misidentified Nicola Fox as being with the Johns Hopkins University Applied Physics Laboratory. She is actually the director of the Heliophysics Division at NASA's headquarters.
AUDIE CORNISH, HOST:
Rogue plasma waves, rapidly flipping magnetic fields - these are some of the surprises that a NASA spacecraft has found near our sun. The Parker Solar Probe blasted off last year on a mission to get closer to the sun than ever before.
NPR's Nell Greenfieldboyce reports that some of what it's seen is so strange, researchers initially thought their instruments were broken.
NELL GREENFIELDBOYCE, BYLINE: The Parker Solar Probe was built to withstand the searing temperatures around the sun. It blasted off in August of 2018. Flybys of Venus help it adjust its orbit so that it gradually gets closer and closer to the sun. So far, it swung close by three times, coming about 15 million miles from the sun. That's a lot closer than the nearest planet, Mercury.
JUSTIN KASPER: The sun's already looking very different from what we've seen before.
GREENFIELDBOYCE: Justin Kasper is an astrophysicist at the University of Michigan. He says one of the biggest findings is something that could explain a long-standing mystery - why the sun's atmosphere is so much hotter than its surface.
KASPER: In apparent violation of, like - oh, I don't know - the second law of thermodynamics.
GREENFIELDBOYCE: He says it's just weird, like if you were walking away from a campfire and, instead of getting colder, the air got hotter.
KASPER: We have to identify some way that energy leaves the sun, travels out into space and then gets deposited.
GREENFIELDBOYCE: He says the Parker Solar Probe might have just found out how that happens. Close to the sun, there are strange features in a plasma called the solar wind, charged particles that are constantly streaming out into space.
KASPER: We'd see suddenly a spike in flow where, in just a couple seconds, the solar wind would start flowing 300,000 miles an hour faster.
GREENFIELDBOYCE: These spikes would only last a few seconds or minutes.
KASPER: But they nearly double the speed of the solar wind. And they're so violent, they actually flip the direction of the magnetic field in the solar wind around.
GREENFIELDBOYCE: The magnetic field kind of reverses itself and then straightens out again. Nicky Fox is director of NASA's Heliophysics Division and was previously the project scientist for the Parker Solar Probe.
NICOLA FOX: It's kind of like twisting, like, a rubber hose. It wants to continually straighten itself again. And so whatever is causing these features, as it is straightening out, it's giving out energy.
GREENFIELDBOYCE: She says all of this could explain what's heating up the sun's atmosphere.
FOX: And so to see the sort of smoking gun for our main questions of heating and acceleration of the solar wind was just an incredible thing.
GREENFIELDBOYCE: These results are reported in the journal Nature, along with plenty of others. For example, the solar wind rotates around the sun far faster than expected. And although the solar system can be a dusty place, it looks like the sun vaporizes or pushes out nearby dust.
FOX: We've actually found a dust-free region close to the sun, and that was first predicted back in 1929.
GREENFIELDBOYCE: The Parker Solar Probe was named after Eugene Parker, a superstar in studies of the sun, who first proposed the existence of the solar wind back in the 1950s. It's the first NASA mission named after a living person. Parker, who's now 92 years old, got to see the rocket launch that carried the probe into space. Fox visited him at his home in Chicago earlier this year.
FOX: I showed him a lot of the early science data, and he was very excited and very moved.
GREENFIELDBOYCE: The probe's next approach to the sun will come in January. Its closest approach will be in 2025, when it will come within 4 million miles of the sun's surface.
Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF RAMIN DJAWADI'S "BLACK HOLE SUN") Transcript provided by NPR, Copyright NPR.