Now four days into its journey, the Parker Solar Probe (PSP) is on its first mission to 'touch' the Sun. What 'touch' actually means in this scenario is that the PSP will be the first ever probe to travel within the Sun's corona; it's outer atmosphere. We can see the Sun's corona when there is a total solar eclipse; when the Moon is positioned between the Earth and the Sun a red aura/glow can be seen around the Moon - this is the otherwise faint glow of the Sun's corona not being obscured by the rest of the Sun's light that we normally see.

But surely we know enough about the Sun already?

The Sun's corona holds yet unsolved mysteries. It is the outermost layer of the Sun's atmosphere, yet is much hotter than either the photosphere and the chromosphere: ~6,000^oC and ~20,000^oC respectively, whilst the corona can have temperatures between 1,000,000^oC and 3,000,000^oC. Another main aspect of the corona that the PSP wishes to investigate is the supersonic solar winds and solar energetic particles at extremely high energies (with speeds of up to more than half that of the speed of light) and what drives both of these mechanisms. These are important questions to ask when it comes to understanding one of the most fundamental astronomical objects that humans first saw. 

The Parker Solar Probe's mission will last seven years, completing 24 total passes of the Sun. The closest approach of the mission will be at roughly 3.8 million miles away from the Sun's surface, but its first approach in November 2018 will see the probe reach 15 million miles away to take its first set of scientific measurements within the corona itself. 

Watch the launch from Sunday here:

For more information, visit these NASA web pages:

NASA, ULA Launch Parker Solar Probe on Historic Journey to Touch Sun

Parker Solar Probe

Thumbnail image credit: NASA/Johns Hopkins APL/Steve Gribben