NASA’s Parker Solar Probe has now marked itself safe from its closest-ever encounter with the sun.

The probe sent a signal just before midnight on Dec. 26, saying it was “alive” and doing fine. This should come as a relief to NASA scientists since communication with the probe “went dark” Christmas Eve when it made its record-breaking closest ever pass — a mere 3.8 million miles from the sun’s surface, according to a NASA blog.

That might seem like a big distance, but in the universe, everything is relative. If the Earth and sun marked opposite end zones of an American football field, the probe’s latest pass took it to the sun’s four-yard line.

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Better Understanding the Sun

The probe is collecting data that will help researchers better understand how the sun “works.” Scientists hope the information will help solve some solar mysteries, like why is the corona 300 times hotter than the sun’s actual surface, which is 300 miles below it? What powers the supersonic solar wind that blows charged particles into the solar system? And what makes those particles move at up to half the speed of light?

“This is one example of NASA’s bold missions, doing something that no one else has ever done before to answer longstanding questions about our universe,” Arik Posner, Parker Solar Probe program scientist at NASA Headquarters in Washington, said in another blog before the probe broke its record. “We can’t wait to receive that first status update from the spacecraft and start receiving the science data in the coming weeks.”

That data will help scientists better understand the Northern Lights because they are generated when the “space weather” driven by the sun’s supersonic winds interacts with Earth’s atmosphere. But there are practical concerns and reasons to understand these forces better as well. Geomagnetic storms can impair GPS satellites and could disable electricity grids.

Scientists expect the probe’s first data transmissions from its close pass around January. This moment has been a long time coming, according to a Johns Hopkins Applied Physics Laboratory timeline.

Long Time Coming

When Eugene N. Parker was a professor at the University of Chicago in the mid-1950s, he predicted the solar wind with mathematical theory. In the 1970s, NASA’s Jet Propulsion Laboratory proposed a flyby mission — but they didn’t yet have the technology — especially the means to protect an instrument from the sun’s heat.

That changed in the 2000s. Scientists developed a carbon composite heat shield that can withstand temperatures up to 2,500 degrees Fahrenheit while holding the probe’s electronics and instruments to 85 F. They also created a cooling system for the spacecraft’s solar panels by pumping pressurized water through titanium radiators, keeping their temps to 320 F while collecting energy to power the craft’s instruments.

Parker was present when the probe launched on August 12, 2018. He died on March 15, 2022, at age 94. The probe holds a plaque with a quote from its namesake: “Let’s see what lies ahead.”

As data begins flowing back from the probe after this and the next two passes, it should provide some answers.

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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.