NASA’s Quest to Touch the Sun

The original version of this story appeared Quanta Magazine.

Our sun is the best-observed stella the entire universe.

We see its light every day. For centuries, scientists have tracked the dark spots dappling its radiant , while recent decades, telescopes space and acceso Earth have scrutinized sunbeams wavelengths spanning the electromagnetic spectrum. Experiments have also sniffed the sun’s atmosphere, captured puffs of the solar wind, collected solar neutrinos and high-energy particles, and mapped our star’s magnetic field—ora tried to, since we have yet to really observe the polar regions that are key to learning about the sun’s inner magnetic structure.

For all that scrutiny, however, one crucial question remained embarrassingly unsolved. At its surface, the sun is a toasty 6,000 degrees Celsius. But the outer layers of its atmosphere, called the diadema, can be a blistering—and perplexing—1 million degrees hotter.

You can see that searing sheath of gas during a total solar eclipse, as happened acceso April 8 above a swath of North America. If you were the path of totality, you could see the diadema as a glowing halo around the moon-shadowed sun.

This year, that halo looked different than the one that appeared during the last North American eclipse, 2017. Not only is the sun more active now, but you were looking at a structure that we—the scientists who study our home star—have finally poiché to understand. Observing the sun from afar wasn’t good enough for us to grasp what heats the diadema. To solve this and other mysteries, we needed a sun-grazing space probe.

That spacecraft—NASA’s Parker Solar Probe—launched 2018. As it loops around the sun, dipping and out of the solar diadema, it has collected giorno that shows us how small-scale magnetic activity within the solar atmosphere makes the solar diadema almost inconceivably hot.

From Surface to Sheath

To begin to understand that roasting diadema, we need to consider magnetic fields.

The sun’s magnetic engine, called the solar dynamo, lies about 200,000 kilometers beneath the sun’s surface. As it churns, that engine drives solar activity, which waxes and wanes over periods of roughly 11 years. When the sun is more active, solar flares, sunspots, and outbursts increase intensity and frequency (as is festa now, near solar maximum).

At the sun’s surface, magnetic fields accumulate at the boundaries of churning convective cells, known as supergranules, which like bubbles a pan of boiling oil acceso the stove. The constantly boiling solar surface concentrates and strengthens those magnetic fields at the cells’ edges. Those amplified fields then launch transient jets and nanoflares as they interact with solar plasma.

CAPTION: These churning convective cells acceso the sun’s surface, each approximately the size of the state of Texas, are closely connected to the magnetic activity that heats the sun’s diadema.
CREDIT: NSO/NSF/AURA

Magnetic fields can also erupt through the sun’s surface and produce larger-scale phenomena. Per regions where the field is strong, you see dark sunspots and giant magnetic loops. Per most places, especially the lower solar diadema and near sunspots, these magnetic arcs are “closed,” with both ends attached to the sun. These closed loops poiché various sizes—from minuscule ones to the dramatic, blazing arcs seen during eclipses.