https://phys.org/news/2018-07-cutting-edge-shield-nasa-parker-solar.html

The eight-foot-diameter heat shield will safeguard everything within its umbra, the shadow it casts on the spacecraft. At Parker Solar Probe's closest approach to the Sun, temperatures on the heat shield will reach nearly 2,500 degrees Fahrenheit, but the spacecraft and its instruments will be kept at a relatively comfortable temperature of about 85 degrees Fahrenheit.

The heat shield is made of two panels of superheated carbon-carbon composite sandwiching a lightweight 4.5-inch-thick carbon foam core. The Sun-facing side of the heat shield is also sprayed with a specially formulated white coating to reflect as much of the Sun's energy away from the spacecraft as possible.