Launched in 2018, the Parker Solar Probe has successfully completed seven close flybys of the sun and embarked on its eighth flyby on April 28, 2021, which included a daring dive into the scorching solar corona. During a press conference on December 14 at the annual meeting of the American Geophysical Union (AGU), NASA scientists revealed that the spacecraft has ventured into the sun’s atmosphere on three separate occasions, even conducting an extended five-hour pass.
Operating in the upper region of the sun’s atmosphere, where temperatures soar to approximately 1 million degrees Celsius—exceeding the visible surface temperature of the sun at a mere 5,500 degrees Celsius—the spacecraft has successfully collected atmospheric particles using its specialized instrument, the Solar Probe Cup. This significant achievement of entering and sampling the solar atmosphere is regarded by scientists as a groundbreaking milestone comparable to landing on the moon.
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The Parker Solar Probe approached the Sun at a distance of approximately 13 million kilometers.
“Humanity’s long-awaited moment has arrived,” stated Nicola Fox, Director of NASA’s Heliophysics Division, at the AGU, as she discussed the achievement of the Parker Solar Probe touching the sun.
The sun’s powerful solar winds, consisting of plasma flows and high-energy particles, emanate from the solar corona. These winds are primarily restrained by the sun’s magnetic field, which also limits plasma eruptions from the sun’s surface.
However, when solar winds exceed a specific velocity and surpass the solar atmosphere at a region known as the Alfvén point, they can break free from their magnetic confinement. Yet, the exact location of this point had remained uncertain.
Now, the Parker Solar Probe has provided an answer to this long-standing question. Previous estimates, based on remote imaging of the solar corona, predicted that the Alfvén point would be located around 6.9 to 13.8 million kilometers from the sun’s surface. On April 28, at a distance of approximately 13 million kilometers from the sun, Parker detected conditions consistent with those predictions, marking its first venture into the solar atmosphere.
A Series of Astonishing Discoveries
Scientists revealed in the journal Physical Review on December 14 that solar winds and solar flares, rapid bursts of solar radiation, can impact power grids and disrupt communication networks on Earth.
Nour Raouafi, a scientist involved in NASA’s Parker Solar Probe project and a researcher at the Johns Hopkins Applied Physics Laboratory, remarked, “Our journey has been filled with unexpected surprises as we explore these uncharted territories.”
To withstand the intense heat, engineers developed a heat shield using materials with remarkably high melting points such as sapphire, tungsten, molybdenum, and niobium, according to representatives from the Harvard-Smithsonian Center for Astrophysics (CfA).
“When the cup makes contact and performs measurements, it literally glows red, with certain instrument parts reaching temperatures over 1,000 degrees Celsius and emitting an orange-red light,” explained CfA astrophysicist Anthony Case.
The data collected within the solar corona by the Parker Solar Probe provides unprecedented insights into the sun, enabling scientists to deepen their understanding of the forces that generate immense energy, fueling the sun and other stars.