On May 31st, 2017 we learned about

The Parker Solar Probe’s complicated course to cruise through our Sun’s corona

In a little over a year, NASA is going to investigate what makes the Sun so hot. Like many questions associated with rocket science, this is actually a bit more complicated than you might think. For as much as we’ve figured out about the size and structures of stars thousands of light years away, we still have a lot of questions about exactly how our local star functions. To find out more, we’re sending the Parker Solar Probe, which will get as close as 3.7 million miles above the Sun’s surface. If that seems far away, keep in mind that that’s still close enough to sweep through the Sun’s outermost layer, the corona. Which also, incidentally, is where things are at their hottest.

The way the Sun sheds heat is a bit unintuitive. Even though it’s hot enough to maintain a series of fusion reactions in its core, the Sun’s out layers are somewhere where the heat is. The surface of the Sun, called the photosphere, can get to around 10,340° Fahrenheit, which is such an absurd number it’s hard to really conceptualize. However, the layer sitting on top of that, the chromosphere that makes those pretty loops of plasma in photos, can reach temperatures of 35,540° Fahrenheit. Beyond that is the corona, which can kind of be thought of as the Sun’s version of an atmosphere. It’s a less dense collection of high-energy particles, with temperatures reaching over a million degrees. Figuring out the dynamics that make the surface cooler than the outer “clouds” is one of the tricky questions the Parker Solar Probe will be gathering data on once it arrives in orbit next fall.

Arranging the appropriate orbit

Keeping with the whole “complexity” theme, getting the probe to the Sun in the first place will be tricky as well. The Earth is zipping around the Sun at around 19 miles per second, which means that upon launch, the probe will be too. To get closer to the Sun, the probe will need to slow down significantly, flying against the Earth’s orbit so that it can get in closer to our local star. At one point, plans called for the probe to head out to Jupiter to be able to establish a slower orbit, but the current plan calls for a few loops around Venus instead. In the end, the probe will still arrive at the Sun at a screaming 124 miles per second, which is a good way to deal with being cooked in the corona.

To survive this pass through million-degree heat, the Parker Solar Probe will carry a thick heat shield on one end. At only four-and-a-half inches thick, the carbon composite shield is expected to provide enough protection for some very fast passes through the corona, probably benefiting from the fact that heat transfer isn’t an instantaneous process. Most of the delicate, sciencey-bits should be able to enjoy the trip at around room temperature, even if the local weather is quite a bit hotter than that.


My second grader asked: Why is it the Parker Solar Probe?

Yes, “Parker” doesn’t sound quite as exotic as Juno or Cassini, although the motivation is similar to the latter example. Like Cassini, Hubble and other spacecraft, the Parker probe is named after a contributor to our understanding of space. Eugene Parker predicted solar wind before it had ever been measured, and his picture, a few papers and inscription of his choice will be part of the spacecraft’s payload.

Source: Parker Solar Probe: NASA renames upcoming mission to touch the Sun by Jason Davis, Planetary Society

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