For the first time, a spacecraft has made contact with the sun. During a recent flyby, NASA’s Parker Solar Probe entered the sun’s atmosphere.
“We have finally arrived,” Nicola Fox, director of NASA’s Heliophysics Science Division in Washington, D.C., said December 14 in a news briefing at the fall meeting of the American Geophysical Union. “Humanity has touched the sun.”
Parker left interplanetary space and crossed into solar territory on April 28, 2021, during one of its close encounters with the sun. While there, the probe took the first measurements of exactly where this boundary, called the Alfvén critical surface, lies. It was about 13 million kilometers above the sun’s surface, physicists reported at the meeting, held online and in New Orleans, and in Physical Review Letters on December 14.
“We knew the Alfvén critical surface had to exist,” solar physicist Justin Kasper of the University of Michigan in Ann Arbor said at the news briefing. “We just didn’t know where it was.”