NASA is celebrating a historic milestone – its Parker Solar Probe successfully flying through the Sun’s corona (upper atmosphere). The spacecraft is flying closer to the Sun than any mission in history. The US space agency has described this as a ‘monumental moment”.
Thomas Zurbuchen, the associate administrator for NASA’s Science Mission Directorate, in a statement said the Parker Solar Probe touching the Sun is a monumental moment for solar science. “Not only does this milestone provide us with deeper insights into our Sun’s evolution and its impact on our solar system, but everything we learn about what our own star also teaches us more about stars in the rest of the universe.”
Nicola Fox, director of NASA’s heliophysics division, said humanity has touched the Sun. Craig DeForest, a solar physicist at the Southwest Research Institute in Boulder, Colorado, said this is a huge milestone. “Flying into the solar corona represents one of the large great unknowns.”
The Parker probe is flying even closer towards the heart of the solar system, head-on into the solar wind and into our star’s atmosphere. It cross the Sun’s atmosphere at 9.33am Universal Time on 28 April 2021. It took several months for mission scientists to download and analyse the data it collected.
This probe is said to be worth about USD 1.5 billion. Since its launch in 2018, it has been orbiting the Sun and looping even closer to the solar surface on each pass. A carbon-composite heat shield protects its instruments from temperatures that will eventually soar to 1,370 degrees Celsius.
Nour Raouafi, the mission’s project scientist, said the spacecraft crossed the Alfven boundary when it was around 14 million kilometers, or just under 20 solar radii, from the Sun’s surface. That’s about where team members had expected to find the interface. Some researchers had speculated that the boundary would be rather ‘fuzzy’, but it was instead somewhat sharp and wrinkly. The spacecraft passed into the corona for nearly five hours and then back out again, and might have crossed into it briefly twice more. Inside the corona, the solar wind speed and plasma densities dropped, suggesting the boundary had indeed been crossed. “We are learning new things that we did not have access to before,” Raouafi says.
The Parker Probe, as it crossed the Alfven surface, flew through a pseudostreamer of electrically charged material, inside which conditions were quieter than the roiling environment outside. While inside the corona, the spacecraft also studied unusual kinks in the magnetic field of the solar wind, known as switchbacks.
Scientists knew about switchbacks previously, but the Parker Solar Probe data have allowed them to trace where they come from, all the way down to the solar surface.