This Christmas Eve, a vehicle will travel at incomprehensible speed around a celestial object to bring wonder to the people of Earth — and it’s not Santa’s sleigh.

On December 24 at 6.40am Eastern time, the Parker Solar Probe, a Nasa spacecraft, will pass within 3.8 million miles of the sun’s surface, more than seven times closer than any previous mission has. While surfing across the corona, the sun’s outer atmosphere, Parker will surpass the blistering speed of 430,000 miles per hour, breaking its own record as the fastest object ever made by humans.

“It’s a voyage of discovery,” said Nicky Fox, associate administrator of Nasa’s Science Mission Directorate. “We really are going into the unknown. Nothing has flown through the atmosphere of a star, and no other mission will for a long time.”

Since its launch in 2018, Parker has inched progressively closer to the sun during 21 solar flybys, called perihelions. The mission, a collaboration between Nasa and the Johns Hopkins Applied Physics Laboratory, has revolutionised our understanding of the sun, spotted comets, snapped captivating pictures and yielded insights about Venus.

In addition to its scientific haul, Parker has overcome the technical challenges of flying so close to the sun that the probe’s heat shield must contend with temperatures of nearly 1,093°C.

“We feel comfortable that the mission is doing really well, even way better than we designed it,” said Nour Rawafi, project scientist at the Applied Physics Laboratory. “But it still remains a very high-risk mission. Anything can happen at any time.”

During previous perihelions, the spacecraft traversed a region called the Alfvén surface, where the solar wind — a stream of particles emitted by the sun — escapes into space. But for its 22nd encounter on Tuesday, Parker will fly hundreds of thousands of miles closer, slipping well into a stellar region that has never been explored.

Going deeper into that area of the sun’s atmosphere could offer insights into the “interacting waves” that ultimately may contribute to the solar wind’s acceleration out into the solar system, said Adam Szabo, mission scientist at Nasa’s Goddard Space Flight Centre.

“We have just barely crossed this Alfvén point in previous encounters,” he said.

As a bonus, the sun is currently at its most active state, known as the solar maximum, raising the odds that the probe will witness spectacular pyrotechnics up close. The probe has already braved coronal mass ejections, major blowups that spew the sun’s plasma out into the solar system. The mission team is hoping for stormier solar seas that might illuminate the mechanisms that accelerate the solar wind and heat the sun’s corona.

“If the sun gives us one of these humongous explosions, like a coronal mass ejection, when Parker Solar Probe is very close to the sun, that would be fantastic,” Rawafi said.

The spacecraft will be out of contact until December 27, when Parker is scheduled to send a message back to Earth confirming its health. Assuming all goes well, the probe will transmit observations from the solar frontier over the coming months. Two more perihelions are scheduled for 2025, and Parker has enough fuel for several more years. But it will never venture any closer to the sun.