NASA’s Parker Solar Probe: Closest Ever to the Sun

The Sun is a hot glowing ball of hydrogen and helium 150 million km away from us, and is vital to life on Earth. The Sun’s outer atmosphere, the corona, is 300 times hotter than its outer plasma layer, which appears to defy thermodynamics and is still a mystery. We cannot see the corona directly from Earth unless there is a solar eclipse.

On 14 December 2021, NASA announced that a spacecraft named Parker Solar Probe has entered the Sun’s corona for the first time in human history. This was similar to the moon landing, which led to a boom in space exploration.

The Sun had become inaccessible due to various engineering challenges. In August 2018, NASA launched Parker Solar Probe to uncover the mysteries of the Sun’s corona and solar wind. It is the first mission to be named after a living scientist, Dr. Eugene Parker, who coined the term ‘solar wind’ and gave the theory for the same.

Parker Solar Probe is also the fastest spacecraft ever built by humans. It has made repeated interactions with Venus to move into its closest orbit to the Sun, where it can get inside the Sun’s corona and obtain samples for further analysis. On April 28, 2021, Parker Solar Probe entered the Sun’s magnetic atmosphere 13 million km above the photosphere and was in close contact with the Sun. Parker Solar Probe measured fluctuations in the Sun’s magnetic field and sampled charged particles. It encountered streamers on its way to the sun.

Credit: NASA/Johns Hopkins APL

The spacecraft has a sun-facing shield made of carbon-carbon composites and is designed to withstand 1370 degrees Celsius. The shield has a reflective aluminum coating to avoid any solar radiation absorption. The main instruments are placed in the center of the shield’s shadow and operate at a maximum temperature of 32 °C and this case is ensured by a number of autonomous sensors and reaction wheels to ensure the operation of the main body.

In 2019, Parker Solar Probe discovered that charged particles in the Sun’s magnetic field follow very chaotic paths, called switchbacks. As the spacecraft moves closer to the Sun, the origin of the switchbacks will be explored. The origin of switchbacks is important for understanding the physics of the Sun, because switchbacks are responsible for the acceleration of solar winds and superheating of the corona, and are the points where the magnetic field exerts torque on charged particles bound to the Sun, which affects the Sun. Near the Sun, you’ll find these switchbacks in abundance.

On September 5, 2022, NASA’s Parker Solar Probe navigated through a coronal mass ejection (CME) and its observations are helping to prove a 20-year-old theory of the interaction of CMEs with interplanetary dust in which Comets, Asteroids and even planetary particles are involved. The CME displaced the dust about 6 million miles from the Sun. These interactions can affect space weather, satellites, communications and navigation systems, and even Earth’s power grids and so it is very important to understand these interactions.

“These interactions between CMEs and dust were theorized two decades ago, but had not been observed until Parker Solar Probe viewed a CME act like a vacuum cleaner, clearing the dust out of its path,” said Guillermo Stenborg, an astrophysicist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland.

The next solar encounter of the Parker Solar Probe starts on September 22, 2023, 22:48 UTC.  Parker Solar Probe will reach closest (as close as 6.16 million km) to the Sun in 2025. A lot more discoveries are on the way.

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