Solving Mysteries of the Sun with the Parker Solar Probe

On August 12, 2018, NASA launched the Parker Solar Probe, a spacecraft designed to study the Sun and its environment. Since then, Parker has sped through the inner solar system, equipped with a suite of instruments built to withstand the Sun’s incredible heat, to investigate unresolved mysteries about our nearest star.

Journey to the Sun

Though many observatories on Earth and in space point towards the Sun, Parker is providing new insight by traveling closer to the star than any spacecraft before it. It’s accomplishing this by progressively orbiting closer and closer, using seven flybys of Venus over the last six years. In April 2021, Parker became the first spacecraft to “touch the Sun”—dipping into the Sun’s corona, it’s upper atmosphere. Parker team member and University of Michigan professor Justin Kasper likened his excitement of this milestone to visiting a planet for the first time.

The most recent, and final, Venus flyby has propelled Parker towards its closest approach of the Sun on December 24, 2024. Parker will speed past just 4.51 million miles (7.26 million kilometers) above the solar surface at a record 430,000 miles per hour (700,000 kilometers per hour). Traveling that fast would get you from New York to Tokyo in less than one minute. This milestone caps off several years of discoveries that have reshaped our understanding of our nearest star.

A Complex Solar Wind

Near Earth, the solar wind is a relatively constant flow of plasma, with a few twists and turns. The solar wind is made up of charged particles, such as electrons, which means it carries along with it electric and magnetic fields. The magnetic field will suddenly flip direction causing quick reversals, called switchbacks, of the solar wind.

In 2019, Parker Solar Probe made a major discovery—closer to the Sun, the solar wind is much more complicated than previously known. While these switchbacks occur throughout the solar wind, they are more plentiful near the Sun’s surface. The question then became, what causes them?

Why Is the Corona So Hot?

Understanding the origin of these switchbacks may help solve the mystery of why the corona is so much hotter than the Sun’s surface. By the 1940s, scientists understood that the Sun’s corona, its atmosphere, is weirdly hot—from upwards of 2 million degrees Fahrenheit in the corona to just 10,000 degrees Fahrenheit at the Sun’s surface. In 1958, physicist Eugene Parker theorized about what could be causing this phenomenon, but this problem has stumped scientists for decades as it seems to defy the laws of physics. Parker is providing data that is helping scientists develop a solution to this long-standing problem.

The Origin of the Solar Wind

In 2023, Parker dipped close enough to the Sun to better study where the solar wind is generated on the Sun’s surface. The so called “fast” solar wind was detected emanating from coronal holes, areas where magnetic field lines leave the Sun but don’t loop back to reconnect at the surface. During solar minimum, when the Sun isn’t very active, those holes tend to appear only near the poles. During solar maximum, a period every 11 years when the Sun becomes more active, these holes appear all over the Sun. This allows the fast solar wind to travel directly towards the Earth, increasing aurora on Earth and other space weather effects.

Everything but the Sun

In route to the Sun, the Parker Solar Probe has observed planets and comets, supergiant stars and gamma-ray bursts, and has made discoveries no one was expecting. Several trips by Venus prompted observations of Venus’ surface, imaging its geology in visible light. Parker also supplied new data about Venus’ comet-like tail, which could help us understand how water escaped from the dry planet.

Final Approach

As Parker makes its final approach to the Sun, there are still discoveries to be made, but those already captured are providing deeper insights not only of the Sun, but other stars, and their impacts on the planets that orbit them.