In the darkness before dawn on Sunday morning, a Delta Heavy rocket blasted off from Cape Canaveral, Florida. On board was the Parker Solar Probe, a Nasa spacecraft destined to dart closer to the Sun than any before.
Despite being the closest star to the Earth and the driving source of energy on our planet, the Sun clings tightly to its secrets. The Parker Solar Probe will finally start answering some of the many questions about it. “We’ll be going where no spacecraft has dared go before — within the corona of a star,” explains project scientist Nicky Fox of John Hopkins University Applied Physics Laboratory.
“Space travel is hard. Going to a lot of these places right on the fringes harder still,” says instrument scientist Ralph McNutt, also of Applied Physics Laboratory. “But if we’re going to really understand what’s going on with our world and how it affects us, we have to keep pushing the frontier.”
“How the various plasma physics evolves as it comes from the Sun coming outward first to the orbit of Mercury is the terra incognita of all of this,” says McNutt. Parker Solar Probe will explore this unknown region of the Sun with four instruments capable of measuring magnetic fields, plasma, energetic particles, and the nature of the Sun’s corona and solar wind.
The surface of the Sun is 5,600 degrees Celsius, yet the wispy corona – only visible during eclipses – is millions of degrees hotter. This is a mystery that scientists hope the Parker Solar Probe will help answer. “It’s a bit like if you walked away from a campfire and suddenly got much hotter,” says Fox.
But getting that close to a star isn’t easy. “We have to keep the spacecraft behind the thermal shield at all times,” says McNutt, describing how the Parker Solar Probe will stay tucked behind its nearly 8-foot diameter, 4.5-inch thick heat shield made of carbon composite and carbon foam.
But even with an innovative heat shield designed to withstand up to 1,300 degrees Celsius – temperatures hot enough to melt steel on Earth – while keeping the spacecraft at room temperature, the Parker Solar Probe can’t get too close to the Sun for too long. Instead, Parker will use the planet Venus, doing series of seven flybys over the next seven years to complete 24 close approaches between Mercury and the Sun. Eventually, it’ll get within just 3.8 million miles of the solar surface. Long before then during its first close approach in November, Parker will be closer than any spacecraft has been before.
The spacecraft will also measure the solar wind, tracking the constant outflow and irregular larger eruptions of particles and solar material that drive space weather. “Even though the solar wind is invisible, we can see it encircling the poles as the aurora, which are beautiful – but reveal the enormous amount of energy and particles that cascade into our atmosphere,” says Fox. “We don’t have a strong understanding of the mechanisms that drive that wind toward us, and that’s what we’re heading out to discover.”
Although the solar wind is measured by other spacecrafts farther from the Sun – and tracked closely on Earth due to its potential to produce colourful aurora (or when more intense, disrupt electronics – these will be the first close measurements from the source of high-energy solar particles as they are accelerated up to 1.8 million miles per hour.
That space weather can get more intense during coronal mass ejections when the Sun burps large clouds of particles into space that have their potentially catastrophic impact When asked what would happen if a major event happens while the spacecraft is close to the Sun, McNutt laughs: “It could turn into a very wild ride. But we’ve got backups, and backups on backups, and backups on those in order to be able to get through get through the storm.”
Another set of instruments will investigate the Sun’s magnetic field, a strong jiggling mess of both closed loops and open streamers that may be responsible for why the corona gets so hot. While the probe will be measuring the field for the entire mission, the truly exciting part of these measurements will start around 2021 when the spacecraft starts dipping within the corona. “We’re going close,” says McNutt. The spacecraft will cross the Alfvén point where particles are accelerated faster than the speed of sound, torn free from the surface of the Sun.
Deep within the Sun’s gravity well, the Parker Solar Probe will quickly become the fastest spacecraft, travelling at 430,000 miles per hour relative to Earth when it hits its closest approach in 2024, or fast enough to complete the journey from Paris to Sydney in under two minutes.
The Parker Solar Probe will also be setting a more human record: this is the first spacecraft to be named for a living human. Eugene Parker first predicted the existence of the solar wind in 1958 a year before it was first observed by the Soviet Luna 1 spacecraft, and three years before those observations were confirmed by Nasa’s Mariner 2 spacecraft.
This article was originally published by WIRED UK
