Since it launched last year, NASA’s Parker Solar Probe has made three dives toward the sun as it reached the fastest speed ever clocked by a human-built vehicle. Scientists released the mission’s first batch of findings on Wednesday, revealing that the dynamics of our star are even weirder than once imagined.
Four papers published in the journal Nature describe what the spacecraft observed during its first two flybys, as it passed within about 15 million miles of the surface of the sun. That is about half the distance that the planet Mercury orbits the sun.
“All of this brand-new information about how the way our star works is going to help us understand how the sun drives change in the space environment throughout our solar system,” said Nicola Fox, director of the heliophysics division at NASA, during a telephone news conference on Wednesday.
The information could help scientists develop ways to provide advance warning of solar storms that could knock out satellites and electrical grids or endanger the health of astronauts in orbit.
Blazing Hot Bubble
The sun is essentially a big ball of hydrogen and helium, and for something that we see every day, it remains a complex ball of mystery.
One puzzle that scientists have been pondering for decades: Why is the solar atmosphere superhot?
The surface of the sun — what we see as a yellow disk in the sky — is about 10,000 degrees Fahrenheit. That is toasty, but cool compared with what lies above, in the thin atmosphere known as the corona.
There, the temperatures jump by a factor of 300 or more, to millions of degrees. The corona also accelerates the solar wind — the million-miles-per-hour stream of particles that fly outward from the sun.
Justin C. Kasper, a professor of space sciences and engineering at the University of Michigan and the principal investigator of one of the solar probe’s four instruments, said scientists said they had a hunch that the vibrating of the sun’s magnetic fields — like the plucking of a guitar string — was critical to heating the corona. So they were curious about what the vibrations would look like closer to the sun.
As expected, the vibrations did get stronger. But the instrument also picked up additional, powerful waves. “Kind of like rogue waves in the ocean,” Dr. Kasper said.
As one of the big waves swept the spacecraft, the speed of the solar wind would, within seconds, rise by 300,000 miles per hour. Each wave would last seconds to minutes. “Just as quickly, in seconds, it goes past us, and we’re back in the normal solar wind,” Dr. Kasper said.
The waves were so strong that they could flip the direction of the magnetic field, producing S-shape twists that the scientists called “switchbacks,” like the twisty paths carved in the side of a steep mountain.
“These are very large and energetic events,” Dr. Kasper said. “We’re really excited about this, because we think it tells us a possible path to understanding how energy is getting from the sun into the atmosphere and heating it.”
Where the Wind Blows
With the closer view of the sun, scientists also now have a better idea of where the solar wind originates.
Most of the solar wind measurements to date have been in the neighborhood of Earth, more than 90 million miles from the sun.
Stuart Bale, a physicist at the University of California, Berkeley, who leads an instrument that measures the electric and magnetic fields in the solar wind, said trying to study solar winds from Earth is like observing the waterfall halfway down.
“The water is always flowing past us,” he said. “It is very turbulent, chaotic, unstructured. And we want to know what is the source of the waterfall, what’s at the top. Is there an iceberg melting up there? Is there a sprinkler system? A lake?”
By the time the solar wind reaches Earth, clues about its origin have been jumbled and become difficult to discern.
“We want to know the source of the water, what’s at the top,” Dr. Bale said.
He said that data from the Parker Solar Probe now shows that the so-called slow solar wind, moving at relatively slow speeds of less than a million miles per hour, emerges from what are known as coronal holes — locations associated with sunspots and where hydrogen and helium are colder and less dense — near the sun’s Equator. (Faster solar winds traveling more than a million miles per hour were known to originate from coronal holes near the poles.)
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Touching the Sun
From Aug. 2018: NASA’s Parker Solar Probe is flying through the punishing heat of the sun’s outer atmosphere.
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“Set the controls for the heart of the sun.” In the summer of 2018, the Parker Solar Probe will lift off from Earth. It will spend the next seven years spiraling inward to the center of the solar system. The Parker probe will be the first spacecraft to touch our star. Or any star. It will brush through the halo of hot gases that form the sun’s outer atmosphere: the corona. The surface of the sun looks placid to our eyes, but it is pierced and roiled by strong magnetic fields. The fields trap gas blowing off the Sun and lift it into glowing arcs and streamers. Scientists don’t understand how the corona works, or why it’s hundreds of times hotter than the surface of the sun. The Parker probe will pass closer to the Sun than any mission before it. To get that close, the spacecraft will make seven flybys of Venus over seven years, gradually tightening its elliptical orbit and shifting it closer and closer to the sun. A high-tech heat shield will protect the probe from the punishing radiation and heat of the corona. Within the shield’s shadow, the spacecraft instruments will operate at a comfortable room temperature. As the probe passes close to the sun, it will briefly become the fastest machine ever built by humans, zipping along at a brisk 430,000 miles per hour. The Parker probe is the first NASA spacecraft to be named after a living person. Eugene Parker is an astrophysicist at the University of Chicago. In 1958, he suggested that the sun radiates a constant and intense stream of charged particles. He called it the solar wind. This wind pushes out comet tails and makes the long streamers seen in solar eclipses. With the Parker Solar Probe, scientists hope to learn more about the sun’s turbulent corona. How it accelerates particles, and how it flings huge clouds of fiery gas outward across space. Huge waves of magnetized gas are called coronal mass ejections. If Earth gets in the way of one of these storms, it could be bad news. Our planet is protected by its own magnetic field, but a direct hit from one of these galloping clouds of particles and radiation could disrupt satellites and force astronauts in the space station to take shelter. In 1859, a powerful storm called the Carrington Event produced auroras as far south as Cuba. A solar storm of that size today could cripple satellites and power grids around the world. If successful, the Parker probe’s mission to touch the sun may explain how solar storms form. Scientists hope it might teach us how to predict coronal outbursts more accurately and learn how to endure them. We’ve always depended on the kindness of a star, here on a planet riding the gentle fringe of barely calculable forces. Living with a star is not easy. But we’re learning.
Star Dust
The spacecraft has also been putting together a picture of the cloud of dust surrounding the sun and the corona — bits shed from comets and asteroids that have passed. The dust was thinner closer to the sun, matching the expectations for a long-theorized dust-free zone around the star.
As the Parker Solar Probe gets closer — repeated flybys of Venus in the coming years will eventually nudge it to a trajectory that will take it within four million miles of the sun — it is likely to confirm that observation and reveal new mysteries.
“It’s a bit early to say whether these discoveries actually overturn existing models,” Daniel Verscharen, a space scientist at University College London who wrote a commentary accompanying the Nature papers, said in an email. “They definitely show that there is a lot more happening close to the sun and that it’s absolutely worth going there to explore further.”
A European Space Agency mission, Solar Orbiter, is set to launch in February. While it will not get as close to the sun as the Parker Solar Probe, it will carry instruments that will provide different views and provide more clues on solving the mystery of the solar wind.
Eugene N. Parker, a retired University of Chicago astrophysicist whom the spacecraft is named after, predicted the existence of the solar wind in 1958. “It was humbling to see the probe’s launch and watch it disappear into the night sky,” Dr. Parker, now 92, said in a statement provided by the university. “But now that data is finally coming in and being analyzed, things are getting really exciting.”
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