In August of last year, NASA sent a spacecraft hurtling toward the inner Solar System, with the aim of getting some answers about the mysterious star at the center of our cosmic neighborhood. Now more than a year later, that tiny robot has started to decode some of the mysteries surrounding our Sun’s behavior, after venturing closer to our parent star than any human-made object has before.
That spacecraft is NASA’s Parker Solar Probe, a car-sized vehicle designed to withstand temperatures of more then 2,500 degrees Fahrenheit. Its various instruments are protected by an extra hardy heat shield, designed to keep the spacecraft relatively cool as it gets near our balmy host star. Already, the Parker Solar Probe has gotten up close and personal with the Sun, coming within 15 million miles of the star — closer than Mercury and any other spacecraft sent to the Sun before. “We got into the record books already,” Adam Szabo, the mission scientist at NASA Goddard Space Flight Center for Parker Solar Probe, tells The Verge.
Before the spacecraft’s launch, researchers were particularly interested in learning more about what’s coming out of the Sun. Energetic particles and plasma are continuously streaming from the Sun at all times — a phenomena that’s been dubbed solar wind. This highly energized material makes its way to Earth, causing the dazzling display of the aurora borealis. If we get too much of this stuff, it can sometimes muck up our spacecraft in orbit and even mess with our electric grid. There’s still a lot we don’t know about solar wind, such as what is accelerating this material so much that it can break free from the Sun. Learning the origins of the wind could help us better predict how it will impact us here on Earth.
Thanks to the Parker Solar Probe’s first close pass to the Sun, researchers are learning some surprising things about how the star behaves closer to its surface. The first batch of results and theories are detailed today in four papers published in the journal Nature.
Perhaps the biggest find from the probe so far is that the Sun’s magnetic field is much more volatile closer to its surface, switching its direction back and forth. “What we didn’t expect is for the magnetic field to become really really choppy,” says Szabo. The Sun’s magnetic field is filled with magnetic forces that move in various directions. And up close to the Sun, the direction of the star’s magnetic field would completely turn around a full 180 degrees in little moments known as “switchbacks.” “This is completely unexpected,” says Szabo. “These are significant orientation changes that we did not expect. And so we have been scratching our heads saying, ‘Okay, what can cause this?’”
Szabo says their best guess is that weird magnetic switches are caused by jets of solar wind bursting out of the Sun. Rather than flow out from the Sun in one continuous stream, some of the solar wind comes out in spikes or bursts, traveling faster than the surrounding medium. These “jet-lets,” as Szabo calls them, will stretch out the magnetic field, causing the magnetic forces to turn around completely. It’s possible that these weird magnetic switchbacks may be the reason the solar wind is able to get so fast and break free of the Sun. When the switchbacks occur, the magnetic field may reconnect with itself, causing massive explosions that shoot out high-speed particles from the Sun.
The researchers think that eventually these jets of solar wind run into the solar wind that has already made its way out into deep space, evening out and creating the relatively steady stream of particles that we see from Earth. While it makes sense based on what the Parker Solar Probe saw, the research is still in its early stages. “Now, we are still a bit too far out to sort of declare that this is the final answer to this question,” says Szabo. “Going four times closer to the Sun should really have the answer to this question.”
Researchers discovered lots of other intriguing details from the Parker Solar Probe data, such as how the Sun’s atmosphere rotates closer to the surface, and how dust particles propagate around the Sun — and there’s even more to look forward to. The Parker Solar Probe’s path around the Sun is an ever decreasing spiral, one that will take the vehicle even closer to the center of the Solar System in the years ahead. The spacecraft swings by Venus every so often, using the planet’s gravity to nudge the vehicle closer to the star. At its closest point, the Parker Solar Probe should come within 4 million miles of the Sun.
Right now, the spacecraft is starting its fourth close orbit around the Sun, and today’s results are just from the vehicle’s first orbit. That means there’s still plenty to learn in the months and years ahead as the Parker Solar Probe edges closer to its scorching target. The closer it gets, the more details scientists will unravel — but it’s possible we may never fully understand why our Sun is the way it is. “I’m absolutely confident that we will make significant improvements in our understanding,” says Szabo. “But to declare that there will be nothing left unanswered, I would hesitate to do so.”