First Spacecraft to Touch the Sun — Why We Put It There in First Place

Rebecca Jean T.
4 min readDec 30, 2021

Earlier this year, NASA’s Parker Solar Probe became the first spacecraft to touch the Sun. The Parker Solar Probe was launched in 2018 to study the Sun’s corona. There is much will still don’t know about this mysterious outer layer of the Sun, but NASA hopes to use the probe to aid us in discoveries about the Sun that could also be applied to observations about other stars as well.

Layers of the Sun

Just like the Earth, the Sun has multiple layers that make up its interior. The corona of the Sun can be thought of as a sort of atmosphere for the Sun. Similar to how Earth has its crust as the surface and the air we breathe as the atmosphere, the Sun has a surface and the corona. The word corona means crown and is used to describe structures that surround something in almost every branch of science.

Diagram of the layers of the Sun. Starting from the inside going out, inner core, radiative zone, convective zone, subsurface flows, photosphere, chromosphere, and corona.
Credit: Lumin Learning

The Corona

The Sun’s corona is made of plasma, hot ionized gas. It emits wavelengths mostly in the form of x-rays. The amount of visible light the corona emits is much less than the surface, so the brightness of the surface makes it where we cannot see the corona most of the time. The best views of the corona for Earth-based observations are during a total solar eclipse. Because the Moon blocks out so much sunlight during this time, we can see the corona. Astronomers use this time to observe the corona and collect data.

Image taken during a total solar eclipse. The moon looks like a black circle in the middle, and the corona is a bright soft white light surrounding it.
Credit: NASA/Aubrey Gemignani (Aug. 21th, 2017)

The Big Mystery About the Corona

The Sun’s corona is actually hotter than its surface, a fact that has baffled scientists since its discovery in the 1930s. This is because heat transfer does not usually work in this way, and shouldn’t work in this way. The core of the Sun is powered by nuclear fusion reactions. These reactions are incredibly hot, causing the core to be around 27 million degrees Fahrenheit! The heat from the core disperses as it travels outwards through the Sun, cooling down as it further disperses. By the time it reaches the surface, it is a little under 10,000 degrees Fahrenheit. While this may sound extremely hot, the Sun’s surface is surprisingly…

Rebecca Jean T.

Published author on NASA’s Radio Jove project. Researching science topics to deliver to you in bite-sized stories.