Parker's three closest orbits will bring it within 6.1 million kilometres (3.8 million miles) of the Sun's surface and inside its outer atmosphere, or corona, where temperatures reach millions of degrees Kelvin.
It does have heat shielding, and it's actually pretty wicked, but we'll get into that later. Because first, we have to address those searing temperatures.
As NASA has explained, the trick to protecting Parker lies in the difference between temperature and heat, along with the density of space.
Temperature is a measurement of how fast particles are moving, but heat measures how much energy they actually transfer. In space, you can have particles moving very fast, but not transferring a lot of heat, because there's a lot of space between those particles.
"Similarly, compared to the visible surface of the Sun, the corona is less dense, so the spacecraft interacts with fewer hot particles and doesn't receive as much heat."
That means the heat shield, which protects most of the instruments on board the probe, will only be heated to about 1,644 degrees Kelvin (1,370 C° or 2,500 F°).
It's fantastic technology, really. It's made of two superheated carbon-carbon composite boards, which sandwich a 11.5-centimetre (4.5-inch) carbon-foam core.
The Sun-facing side is painted brilliant white in ceramic paint to deflect as much of the Sun's light as possible; it's about 2.4 metres (8 feet) in diameter. The shield weighs just 72.5 kilograms (160 pounds) because of the lightness of the foam. And, amazingly, it keeps everything behind it at or below 300 Kelvin (30 C° or 85 F°).
https://www.sciencealert.com/nasa-parker-solar-probe-why-it-won-t-melt-technology-science-heat-space