NASA’s Parker Solar Probe to fly through sun’s corona

In 2018, NASA scientists launched the Parker Solar Probe on what they call “a mission to touch the sun.” Since then, the spacecraft has looped around our star 21 times, with the research team nudging the craft’s orbit ever closer to the solar surface. Now, the probe is on track for its closest approach yet. On December 24, the Parker Solar Probe will zip through the solar corona at about 690,000 kph, passing within 6.1 million km of the star’s surface.

“Every time we get closer, we are spending more time within the atmosphere of the sun,” says solar astrophysicist and project scientist Nour Rawafi, from the Johns Hopkins Applied Physics Laboratory where the probe was designed and built. Explosions of plasma and solar magnetic field that emerge from this part of the sun can cause brilliant auroral displays and are powerful enough to interfere with power grids and telecommunications.

Scientists have spent decades studying heliophysics from afar to get an idea of how energy is transferred within the corona to create coronal mass ejections and other solar weather. Every solar approach the probe makes, Rawafi says, “will help us get the fingerprints of these complex physical processes while they are developing.”

During the flyby, the spacecraft will be operating in one of the solar system’s most extreme environments. It took about six years for researchers to develop a heat shield for the spacecraft. Called the Thermal Protection System, it consists of 4.5 inches of gritty black carbon foam sandwiched between carbon fiber plates. The shield sits at the front of the craft and flight controllers ensure it’s always facing the sun. Its outer plate is coated with a specially made white ceramic which reflects light and heat away from the craft’s payload of instruments. At its closest approach, the heat shield’s surface “will be at about 1,800 to 1,900 °F,” Rawafi says. But the craft’s payload of instruments will sit comfortably at room temperature.

The Parker probe’s payload contains multiple suites of instruments. One snaps images, others measure magnetic field strength and particle properties. Insights from the collected data will have implications for predicting space weather, and help scientists understand how the sun creates and defines its solar system, says David Malaspina, a researcher at the Laboratory for Atmospheric and Space Physics. He was one of the scientists who developed the proposal for the Parker Solar Probe in 2008.

The data from the probe’s previous flybys confirmed a century-old hypothesis that there’s a dust-free zone around the sun, Malaspina says. Those approaches also revealed the existence of switchbacks within the magnetic field of the solar corona. In these areas, the magnetic field carried by the solar wind doubles back on itself as the stream of plasma shoots outwards into space.

This was not the only coronal surprise the Parker Solar Probe has revealed. Recently, a PhD student working with Malaspina, Benjamin Short, found indications of relatively quiet areas within the solar corona where the magnetic field and plasma remained stable. Unexpectedly, the fraction of solar wind displaying these calm characteristics seems to increase closer to the surface (Astrophys. J. 2024, DOI: 10.3847/1538-4357/ad7b13). “It’s sort of like getting closer to a hurricane,” Malaspina says, “but finding more and more patches of total quiet.”

The scientists involved with the mission are excited to see what this deepest dive into the solar corona reveals about our nearest star. “Now the mission is achieving its full purpose and traveling as close to the sun as it possibly can,” Malaspina says. “It’s been a long journey.”

The spacecraft’s journey will not end with this approach. The Parker Solar Probe is scheduled to fly by the sun at the same distance twice more next year. After that, NASA will likely choose to extend the mission, Rawafi says.

An extension will provide scientists with data on how the corona fluctuates over a full 11-year solar cycle. Both the spacecraft and payload are still in great condition and the future of the probe is bright, he says, adding “in 1969 we landed humans on the moon. And Christmas Eve of 2024, we are embracing a star.”