The Parker Solar Probe (PSP; previously Solar Probe, Solar Probe Plus or Solar Probe+) is a NASA space probe launched in 2018 with the mission of making observations of the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million km or 4.3 million miles) from the center of the Sun, and by 2025 will travel, at closest approach, as fast as 690,000 km/h (430,000 mph) or 191 km/s, which is 0.064% the speed of light. It is the fastest object ever built.