This weekend, the European Space Agency and NASA are launching a new, hardened spacecraft bound for the center of our Solar System, where it will get a view of our Sun that no vehicle has seen before. The probe, dubbed the Solar Orbiter, will be tasked with observing the Sun’s poles, in hopes of better predicting how our parent star behaves.
Up until now, practically all vehicles we have sent toward the Sun have stuck around the star’s mid-section, orbiting in line with all the planets in the Solar System. But the Solar Orbiter is set to fly a path around the Sun at a high angle, so that it can get a glimpse of the polar regions that have eluded our observations for so long. Just like Earth, the Sun also has poles on its “top” and “bottom,” but they’ve been hard to see since our planet orbits near the Sun’s equator.
Once in this lopsided orbit, the Solar Orbiter will come within 26 million miles, or 42 million kilometers, of the Sun, gathering images and data from a truly unique vantage point. Hopefully, this new information can help scientists figure out some of the mysteries of our star that have remained unsolved for decades. Specifically, they want to know what drives our star’s strange 11-year cycle, where it alternates between times of intense activity and times of quiet.
“We understand the cyclic behavior; we’ve observed it for 400 years, ever since people have pointed the telescope at the Sun,” Daniel Müller, the ESA’s project scientist for the Solar Orbiter mission, tells The Verge. “But we don’t really know why it is 11 years and obviously [what drives] the strength of the cycle.”
The 11-year itch
At the beginning and end of its 11-year run, the Sun’s massive magnetic field completely switches direction. During this impressive flip the poles essentially trade places, going from positive to negative or from negative to positive.
The strange process dictates how the star is going to behave for the next decade. During this 11-year period, the Sun alternates between what’s known as solar maximum and solar minimum. When the Sun is at solar maximum, sunspots dominate its surface, while the Sun is relatively sunspot-free during solar minimum.
This sunspot cycle also coincides with just how much junk the Sun sends our way. Highly energized particles are constantly breaking free from the Sun and speeding outward in all directions, eventually making their way to Earth. But when the Sun is at solar maximum, this particle parade gets much more volatile and intense. The Sun’s solar flare activity heats up, and the star will burp up a whole bunch of particles at a time, which carry pieces of the Sun’s magnetic field — creating a highly energized chaotic cocktail that zooms toward our planet.
Fortunately, our planet has its own strong magnetic field that acts like an umbrella, shielding us from most of the Sun’s particles. But when a large influx of solar plasma heads our way, it can be an issue. These events can perturb our magnetic field and trigger geomagnetic storms — also known as space weather events. This can potentially muck up spacecraft that are in orbit around Earth, like our GPS satellites, and heighten the radiation risk to astronauts on the International Space Station. A strong enough storm can even disturb the power grid on the ground.
Scientists have been trying to better understand this behavior for decades, so that we can best prepare for potential storms. “What we want to be able to do is reliably forecast space weather conditions in the Earth environment,” says Müller. Researchers have gotten good data of the Sun’s magnetic field from its middle, but since the poles are an important part of this flipping process, scientists are eager to observe them as the Sun evolves. “We’re missing the key part, which is at the poles,” says Müller.
Surviving the Sun
That’s where Solar Orbiter comes in. Roughly the size of a small bus, the box-shaped spacecraft houses 10 instruments, designed to take images of the Sun’s surface, as well as gather data on the star’s magnetic field, its atmosphere, and more. These precious tools are protected by Solar Orbiter’s most essential piece of equipment: its heat shield.
The shield is a large rectangular piece of titanium that adorns one side of Solar Orbiter. It is coated with a special material called SolarBlack that can absorb the intense heat from the Sun, preventing Solar Orbiter’s instruments from getting fried. Thanks to the design, the shield will be able to withstand blazing temperatures of more than 1,100 degrees Fahrenheit (around 600 degrees Celsius).
“Behind the heat shield the rest of the spacecraft is hiding, and we have to keep that heat shield pointing at the Sun for the entire duration, unless we’re doing maneuvers,” says Ian Walters, the project manager for Solar Orbiter at Airbus, which built the spacecraft.
Of course, the instruments will need to look at the Sun from time to time to get the data that they need. Engineers have built little doors into the heat shield that will open and close every so often to allow some of the instruments to get a view of the Sun. Taking measurements will heat the instruments up, but a special radiator at the base of the heat shield should conduct the heat away from the instruments and out into space.
If it all works, then Solar Orbiter will get some of the closest images ever taken of our Sun’s surface. “At closest approach, it will roughly be three times better resolution than anything we’ve seen so far on ground,” says Müller.
Eyes on the star
Solar Orbiter is set to launch late Sunday night at 11:03PM ET from Florida, out of the newly renamed Cape Canaveral Space Force Station. Its ride into space is an Atlas V rocket, operated by the United Launch Alliance. It’ll then spend the next two years traveling toward the Sun, swinging by Earth and Venus a few times to pick up speed and get into its angular orbit around the star.
It’s a similar route to one that another NASA spacecraft took towards the Sun two years ago. In 2018, NASA launched a solar-bound spacecraft called the Parker Solar Probe, which has gotten closer to the Sun than any human-made vehicle has come before. The mission has already gathered valuable data about the Sun that is better shaping our understanding of how the celestial body works. Like most other solar vehicles, the Parker Solar Probe is orbiting in line with the planets and it’s not equipped with a camera. Solar Orbiter will be able to complement that mission with its unique route and instruments. “There’s an amazing amount of synergy between these two missions,” says Müller. “They’re not really competing with each other. They really have complimentary focal points.”
Above all, Müller says he’s excited for Solar Orbiter to venture to a new region of our Solar System that we’ve never really been to before. Going to these unexplored poles means scientists will probably learn something new. “This is really something that no one can tell you what will it look like exactly,” says Müller. “But we really hope that we can fill in this blind spot in our knowledge of the Sun.”