Read: Astronomers can’t decide what the sun is made of
To ponder the unknowns feels like sitting with an inquisitive toddler. Why is the sun’s outer atmosphere, the corona, so hot? Where does the solar wind come from? Why does it shoot out of the corona like that? What makes the sun flare up sometimes, shooting even more excited particles out into space? These are some of the questions that scientists hope Parker can answer before its mission ends in 2025, with a fiery plunge right into the sun.
NASA released the first batch of results this week, published across four papers in Nature. The findings come from measurements of the corona, which is, remarkably, hotter than the surface itself. The corona extends millions of miles from the surface into space. The region is only visible to the naked eye during a solar eclipse, when the moon casts a shadow on the Earth and blocks out the sun, leaving only a golden ring hanging in a darkened sky.
The corona unleashes powerful streams of high-energy particles, known as the solar wind, which can be felt all across the solar system, and far beyond Pluto. The data from the Parker probe show that the solar wind is far more turbulent near the sun than in our own vicinity, tens of millions of miles away. The wind drags the sun’s magnetic field out into space, and even bends the field enough for magnetic forces to completely flip around for a few minutes at a time, pointing back at the sun itself instead of into space. The researchers weren’t expecting the strength of this effect, as well as how often it seems to occur.
Scientists also found that shifts in the sun’s magnetic field speed up the particles flowing away from the sun much faster than any of their models had predicted. Astronomers have spent decades probing the depths of countless distant stars in the cosmos, some of them billions of light-years away, but their own still keeps secrets from them.
Read: Where is our sun’s twin?
Scientists haven’t been able to make such close-up detections with instruments on Earth, or even with earlier missions to the sun, which never got as close. For studying the sun, proximity is everything. “Imagine that we live halfway down a waterfall, and the water is always going past us, and we want to know, what is the source of the waterfall up at the top?” says Stuart Bale, a scientist at the University of California at Berkeley, and the lead on a Parker instrument that examines the solar wind by measuring magnetic fields. “Is there an iceberg melting up there? Is there a sprinkler system? Is there a lake, a hole in the ground? And it’s very hard to tell from halfway down. So what Parker has done is got us closer than ever to the sun.”
At every close approach, the Parker probe will also get closer to pulling off one of the toughest feats of robotic space exploration. It sounds counterintuitive, but it’s actually harder to reach the sun than it is to leave the solar system altogether. The sun’s gravity is always tugging at everything around it, from giant planets to tiny moons, but those objects are also looping around the sun at great speeds, which keeps them from falling toward it. “To get to Mars, you only need to increase slightly your orbital speed. If you need to get to the sun, you basically have to completely slow down your current momentum,” Yanping Guo, the mission-design and navigation manager for the Parker Solar Probe, explained to me.