After spending 990 days speeding through the solar system and zipping around Venus and our home star, NASA's Parker Solar Probe has achieved the headline goal of its mission:
More specifically, an instrument aboard the probe,, notified scientists back on Earth that the spacecraft had crossed a critical threshold and was within the sun's corona -- a furnace of unfathomable proportions, where temperatures can reach up to 3 million degrees Fahrenheit.
The announcement was made at the annual meeting of the American Geophysical Union in New Orleans on Tuesday.
Michael Stevens, an astronomer at the Center for Astrophysics (CfA), Harvard and the Smithsonian, explained that the probe had to cross the Alfvén point, a fuzzy layer where the sun's magnetic field holds the star's plasma and wind tightly. An instrument on Parker, developed by CfA, determined that Parker had passed the point three times on April 28 -- entering the corona and high-fiving the sun.
Parker is a remarkable probe. It's the fastest laboratory ever built, using gravity to swing around Venus and the sun and to gather speed across its orbit. It's also the closest human-built object to the sun -- its recent closest approach, in November, put it within 5.3 million miles of the sun. For reference, Mercury is around six times further away, at 36 million miles.
There are dangers in cozying up to the star. Earlier this year, scientists working with Parker reported that the probe was. Parker has a state-of-the-art heat shield that keeps it from overheating, though the CfA instrument that deemed Parker had touched the sun is exposed to the elements.
Though the solar squeeze is an important milestone for Parker, there's still much to learn about the sun. Parker will continue to swing by the sun, collecting data from within the corona about the solar wind and plasma,. In 2023, it'll get even closer, coming within just 4.9 million miles. As long as it survives those plasma explosions, its closest approach will occur three years from now when it comes within 4.3 million miles.