Our fastest jets can cross the country in a few hours. Rockets that carry astronauts reach thousands of miles per hour. But there's one machine that makes all of them look like they're standing still, and it spends its time diving toward the Sun.
It's NASA's Parker Solar Probe, the fastest object ever built by humans. When it swept closest to the Sun in December 2024, it was traveling about 430,000 miles per hour, or roughly 118 miles every second. That's almost three times faster than the previous record holder, a spacecraft called Helios 2. Even so, that's only about 0.064 percent of the speed of light.
A Mission to Touch the Sun
The Parker Solar Probe launched on August 12, 2018. Its job is to study the Sun's corona, the wispy outer atmosphere you can see during a total solar eclipse. It's the first spacecraft ever to fly into the low corona. It was designed and built by the Johns Hopkins University Applied Physics Laboratory.
Scientists had wanted to send a probe like this since 1958, but it kept getting postponed because of cost. The final mission cost NASA about $1.5 billion. On December 24, 2024, it made its closest pass yet, coming within about 3.8 million miles of the Sun's surface. Mission controllers had to wait until December 26 to hear its signal and confirm it had survived.
Why It Goes So Fast
The probe doesn't have a giant engine pushing it to those speeds. Gravity does the heavy lifting. The probe travels in a long, stretched-out orbit, and just as a ball speeds up rolling downhill, it picks up speed as it falls toward the Sun, then slows again as it swings back out.
Getting that close took clever planning. The probe used a series of flybys of Venus, using the planet's gravity to reshape its orbit and bring it nearer and nearer to the Sun. During an earlier pass in 2023, it was already moving fast enough to fly from New York to Tokyo in just over a minute.
How It Survives the Heat
Near the Sun, sunlight is about 475 times more intense than it is here at Earth. To survive, the probe carries a six-sided heat shield about 7.5 feet across and just 4.5 inches thick. It's made of two panels of reinforced carbon composite around a lightweight carbon foam core.
The shield can handle about 2,500 degrees Fahrenheit on its sunny side, yet it weighs only about 160 pounds. Behind it, the instruments stay at a comfortable 85 degrees, about like a summer afternoon.
Named for a Living Legend
The probe was the first NASA spacecraft named after a living person, physicist Eugene Parker of the University of Chicago. Back in the 1950s, he developed a theory predicting the solar wind, the stream of particles constantly flowing out from the Sun.
The spacecraft carries a memory card with the names of more than 1.1 million people who signed up to come along, plus photos of Parker and a copy of his 1958 scientific paper. The mission has since been extended to 2029.
When its fuel finally runs out, the probe's instruments are expected to be destroyed by the Sun's heat. But its tough heat shield is expected to keep circling the Sun for millions of years, a lasting little monument to human curiosity.
