Early on Christmas Eve in 2024, a NASA craft swooped at blazing speed through the sun's atmosphere.
The Parker Solar Probe, equipped with a robust heat shield, made the closest-ever approach to our dynamic star, coming some 3.8 million miles (6.1 million kilometers) from the stellar surface. That's seven times closer than any other probe. The mission is designed to fly into the sun's corona, or outer atmosphere, which spawns many of the powerful solar storms and weather that impact Earth.
To understand our star's behavior, a craft had to go where no craft had gone before.
"It's really exciting," Nour Raouafi, an astrophysicist at the Johns Hopkins Applied Physics Laboratory and project scientist for the mission, told Mashable. "The sun is like a laboratory to us."
Though the lab announced the craft made the historic flyby on Christmas Eve, the probe will be in position to send a beacon tone to Earth on Dec. 27, which will confirm its safety.
To make this record-breaking pass, the nearly 10-foot-long probe has made 22 orbits around the sun, allowing it to swoop ever deeper into the corona. And while doing so, the spacecraft has been continually picking up speed. When you repeatedly swing by such a massive and gravitationally powerful object — the sun is a sphere of hot gas 333,000 times as massive as our planet — you accrue lots of speed. Out in space, there's nothing to stop this motion.
On this close flyby, the probe reached some 430,000 miles per hour (692,000 kilometers per hour).
"It's the fastest human-made object ever."
"That's like going from Philadelphia to Washington, D.C. in one second," marveled Raouafi. "It's fascinating. It's the fastest human-made object ever."
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The spacecraft can survive such an extreme plunge into the corona because it's fitted with a robust heat shield designed to withstand intense solar radiation. The shield itself, which is eight feet (2.4 meters) in diameter and 4.5 inches (nearly 12 centimeters) thick, heats up to some 2,500 degrees Fahrenheit, but just a couple of feet behind the shield, the environs are surprisingly pleasant. The instruments operate at round room temperature.
Why Parker Solar Probe swooped into the sun
In 2022, the probe flew into "one of the most powerful coronal mass ejections (CMEs) ever recorded," NASA explained. A CME is the eruption of a mass of super hot gas (plasma) into space.
Raouafi hopes it happens again. (The sun is in an active state, so the odds are about as good as they get.)
When the sun unleashes an explosion of energy and particles, the corona accelerates these particles. Such solar storms have huge implications for our energy grids and communications systems on Earth, as well as for astronauts in space — particularly as NASA prepares to return astronauts to the moon, and eventually, beyond.
"That's why we want to fly through regions where these particles are accelerated," Raouafi said. "We want to understand how the acceleration is done."
The Parker solar probe's researchers expect the spacecraft, fitted with instruments to measure and image the solar wind (a constant stream of charged particles emanating from the corona), will enable us to better forecast when and where a potent CME or solar flare may hit.
For example, when a CME erupts from the sun's surface, it must travel over 92 million miles to reach Earth. Along the way, this hot gas will "pile up" the solar wind ahead of it.
"That will affect its arrival time to Earth," Raouafi explained. Knowledge about these space dynamics is critical: A good space weather forecast would allow power utilities to temporarily shut off power to avoid conducting a power surge from a CME, and potentially blowing out power to millions.
Infamously, in 1989, a potent solar flare-associated CME knocked out power to millions in Québec, Canada. The CME hit Earth's magnetic field on March 12 of that year, and then, wrote NASA astronomer Sten Odenwald, "Just after 2:44 a.m. on March 13, the currents found a weakness in the electrical power grid of Quebec. In less than two minutes, the entire Quebec power grid lost power. During the 12-hour blackout that followed, millions of people suddenly found themselves in dark office buildings and underground pedestrian tunnels, and in stalled elevators." The same solar event fried a $10 million transformer at Salem Nuclear Power Plant in New Jersey.
"Hopefully we'll see something that surprises us quite a bit."
Following this Christmas Eve journey through the corona, the probe has two more planned passes in March and June 2025 that will bring it a similar distance to the sun. This is true exploration into uncharted territory, a place where scientists seek the unexpected.
"Hopefully we'll see something that surprises us quite a bit," Raouafi said.
