A US spacecraft will swoop inside the Sun's corona, its superheated outer atmosphere, on a pathfinding mission to learn more about how stars work. Nasa's $1.5bn Parker Solar Probe, which will be protected by a shield that can withstand temperatures of 1,400C, will journey within 6m km of the Sun's surface, seven times closer than any previous spacecraft. From a report: Set to kick off next July, the plan is to plunge the Parker Solar Probe into the Sun's corona -- the hazy bit you can see around the edges of the Sun during a total solar eclipse -- to study this phenomenon. The car-sized spacecraft will get closer to the Sun than any other mission ever has. Travelling at the dizzying speed of more than 720,000 kilometres per hour, the probe will eventually come within less than 6.4 million kilometres of the Sun's surface. We've been studying the Sun for thousands of years, and even though we now have remote sensing observatories and spacecraft that examine it in spectacular detail, many questions still remain. The two big ones are: 1. Why is the corona on the outside of the Sun at least 300 times hotter than the surface? 2. Why does the solar wind speed up?