NASA’s Parker Solar Probe Buzzes the Sun to Unlock Secrets of Our Host Star

Data beamed back from the heat-tolerant probe could help explain why the sun’s outer atmosphere, or corona, which reaches temperatures of 3.5 million degrees Fahrenheit, is hundreds of times hotter than its surface, according to the scientists. The data could also yield new insights into the origin of solar wind, the potentially dangerous stream of charged particles and hot gas that blasts out into space from the sun’s surface.

“These are mysteries that have been bugging us for decades,” said Nour Raouafi, an astrophysicist at the Johns Hopkins Applied Physics Laboratory and the project scientist for the probe.

Dr. Raouafi was one of five mission scientists who discussed the probe’s historic flyby in New Orleans at a meeting of the American Geophysical Union. The flyby was detailed in a paper published Tuesday in the journal Physical Review Letters.

Previously, scientific data about the solar wind came only from Earth- and space-based telescopes, other spacecraft operating farther from the sun and lunar experiments conducted decades ago by Apollo astronauts.

Images taken by a camera aboard the probe helped Dr. Raouafi’s team confirm that the probe had crossed the corona’s upper boundary, or what astronomers call the Alfvén critical surface. The boundary—which the probe showed to be wrinkly rather than smooth—marks the point at which material rising from the sun escapes the star’s gravity and magnetic forces, and streams outward as the solar wind at speeds of up to 1.7 million miles an hour.

“What we’re seeing now is that the sun is like a balloon that has a bunch of little holes punched in it with the wind coming out of those little holes with different speeds and densities,” said Stuart Bale, a University of California, Berkeley, astrophysicist and one of the scientists who described the flyby at the meeting.

In addition to a camera, the probe is equipped with instruments that measure electromagnetic fields and charged particles inside the corona—all protected by an 8-foot-wide heat shield designed to withstand extreme temperatures.

With the probe to buzz the sun 14 more times over the next four years, Dr. Bale said he expects future data will help answer more questions about the sun. On the flybys to come, the probe is projected to come even closer to the sun—within 3.8 million miles during its final passes in 2024 and 2025.

The sun is about 93 million miles from Earth.

The final flybys are expected to coincide with what astronomers call the solar maximum, a period that comes every 11 years during which outbursts of energy from the corona known as coronal mass ejections and similar phenomena are especially intense.

Scientists are eager to obtain reliable data on the solar maximum, as the outbursts have the potential to trigger electrical blackouts, scuttle banking systems and disable global positioning satellites, according to scientists. The outbursts also pose a threat to airplane passengers and astronauts—including those who one day might colonize the moon and Mars.

“Once we start talking about people leaving the magnetic bubble of earth, which protects us from cosmic rays and solar particles, we need to be able to predict how those particles propagate,” said Cindy Cattell, a University of Minnesota physicist who attended the meeting but isn’t involved with the mission. “Perhaps we can improve those predictions with data from the Parker probe.”

The probe was named for Eugene Parker, a University of Chicago astrophysicist who first predicted the existence of solar wind in 1958.