NASA’s Parker Solar Probe and the Curious Case of the Hot Corona

Most of what we know about the corona is deeply rooted in the history of total solar eclipses. Before sophisticated instruments and spacecraft, the only way to study the corona from Earth was during a total eclipse, when the Moon blocks the Sun’s bright face, revealing the surrounding, dimmer corona.

The story of the coronal heating problem begins with a green spectral line observed during an 1869 total eclipse. Because different elements emit light at characteristic wavelengths, scientists can use spectrometers to analyze light from the Sun and identify its composition. But the green line observed in 1869 didn’t correspond to any known elements on Earth. Scientists thought perhaps they’d discovered a new element, and they called it coronium.

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Credits: NASA’s Goddard Space Flight Center/Gopalswamy

Most of what we know about the corona is deeply rooted in the history of total solar eclipses. Parker Solar Probe will fly through this very region, seeking clues to the Sun’s behavior. This photo was taken in Madras, Oregon, during the total solar eclipse on Aug. 21, 2017.

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Credits: NASA’s Goddard Space Flight Center/Lisa Poje/Genna Duberstein

Above the surface, the corona (illustrated here) extends for millions of miles and roils with plasma. Eventually, it continues outward as the solar wind, a supersonic stream of plasma permeating the entire solar system.

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Credits: NASA/JAXA/Hinode

A closeup of the Sun’s convective, or boiling, motion, with a small sunspot forming on the right, from Hinode, a collaboration between NASA and the Japan Aerospace Exploration Agency (JAXA). The outer layers of the Sun are constantly boiling and roil with mechanical energy. This fluid motion generates complex magnetic fields that extend far up into the corona.

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Credits: NASA/Johns Hopkins APL

Artist’s concept of NASA’s Parker Solar Probe. The spacecraft will fly through the Sun’s corona to trace how energy and heat move through the star’s atmosphere.

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Temperatures in the corona — the Sun’s outer atmosphere — spike to 3 million degrees Fahrenheit, while just 1,000 miles below, the underlying surface simmers at a balmy 10,000 F.

How the Sun manages this feat is a mystery that dates back nearly 150 years, and remains one of the greatest unanswered questions in astrophysics. Scientists call it the coronal heating problem.

Explains NASA’s solar spacecraft probe and its journey into the sun. Describes the Parker Solar Probe launching in 2018. Describes its makeup, composition, mission goal, and what it will face while circling the Sun.