A new space probe will study the sun’s corona and the solar wind

UNTIL February, when the first of SpaceX’s Falcon Heavy lifters was launched, the world’s most powerful rocket was the Delta IV Heavy. On August 11th, if all goes according to plan, one of these will take off from Cape Canaveral carrying a craft called the Parker Solar Probe.

This probe, as its name suggests, is designed to get close to the sun. The rules of orbital mechanics mean that requires a lot of energy. Hence the need for a launcher as powerful as the Delta IV Heavy. A combination of rocket thrust and a series of gravitational “assists” from Venus will put the probe in a long, looping solar orbit. At its closest, it will fly within 6m kilometres of the nearest thing the sun has to a surface—the top of the layer known as the photosphere, which the naked eye perceives as the solar disc. That will bring it 85% closer to the photosphere than Mercury, the planet closest to the sun, ever gets.

This path will take it through the corona, a shell of superhot plasma...