On Aug. 6, the Parker Solar Probe will launch from the Kennedy Space Center in Florida for one extremely intense mission: to fly closer to the sun than any spacecraft before.
The probe will fly through and study the sun’s atmosphere, where it will face punishing heat and radiation. At its closest, it will come within 6.1 million kilometres of the sun.
“A lot of people don’t think that’s particularly close,” said Nicola Fox, the project scientist for the Parker Solar Probe. “But if I put the sun and the Earth in the end zones in a football field, the Parker Solar Probe will be on the four-yard line in the red zone, knocking on the door for a touchdown.”
Named after astrophysicist Eugene Parker — the first living researcher to receive such an honour — the probe will travel in the sun’s outer atmosphere, called the corona. Because it isn’t very dense, the corona is difficult to study. The only time we can see it is during a solar eclipse, or with a specially made instrument called a coronagraph, which blocks out the sun’s light.
While the sun is vital to our existence, it’s not really our ally. It is a roiling, churning ball of gas and charged particles that generates a solar wind that influences our planet — and not always in a good way.
Solar flares are one example. These eruptions occur in cooler regions of the sun, called sunspots. Just like Earth, the sun has a magnetic field. But unlike Earth, different regions of the sun rotate at different speeds. This can cause magnetic loops to become tangled. After twisting tighter and tighter, the stored energy is released as a solar flare.
These are often followed by coronal mass ejections, where charged particles (plasma) erupt and travel at increased speeds along the solar wind.
These events can cause radio blackouts and even knock out power grids. One of the most well known is the power outage that left six million people shivering in the dark in Quebec in March 1989.
“It’s of fundamental importance for us to be able to predict space weather much like we predict weather here on Earth,” said Alex Young, a solar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., during a news conference Friday.
With the Parker Solar Probe mission, scientists want to better understand these phenomena: the sun’s corona, magnetic field, solar flares and the wildly fast solar wind.
“The solar wind goes from a steady breeze to a supersonic flow from the corona to millions of miles an hour,” Young said. “So why does this happen? What is going on here?”
The way the sun works is counterintuitive.
“It’s a very strange, unfamiliar environment for us. We’re used to the idea that, if I’m standing next to a campfire and I walk away from it, it gets cooler. But this is not what happens on the sun,” Young said. “As we go from the surface of the sun, which is 10,000 degrees, and quickly move up into the corona, we find ourselves quickly at millions of degrees.
This mystery “drives not only how this star works, our sun, but also all the stars in the universe,” Young said.
Why it won’t melt
Clearly, a spacecraft the size of a small car flying that close to the sun needs some serious protection.
The Parker Solar Probe actually won’t be facing the million-degree temperatures that the sun generates. It’s important to note there is a difference between temperature and heat. Temperature measures how fast particles are moving, while heat measures the total amount of energy that is transferred. The particles may be moving fast but if there are few of them they won’t transfer that heat.
Scientists explain it this way: It’s the difference between putting your hand in an oven (not touching anything) and in a pot of hot water. Your hand would burn in the water because it is in contact with many more particles compared to in the oven, where it could withstand the same temperature for a longer duration.
Since the sun’s corona isn’t very dense, the spacecraft won’t be interacting with many particles.
That being said, it will still have to endure temperatures near 1,400 C.
For that, it is equipped with a white ceramic shield — built out of reinforced carbon and carbon foam — that will only ever face the sun.The solar arrays that provide power to the probe retract upon each close approach, so little is exposed to the sun’s powerful rays, while a cooling system also helps to prevent the spacecraft from frying.
It takes eight minutes for the sun’s light to reach us, and the same goes for any message from the probe. Being so close to the sun, the autonomous spacecraft needs to be able to make quick decisions.
If all goes well, the Parker Solar Probe will launch on Aug. 6 and arrive safely on Nov. 1. It will then begin its 88-day orbit of the sun that will take it out past Venus. At its closest approach, which will be in 2024, it will be travelling 692,000 km/h.
The probe will complete 24 orbits with seven gravity assists around Venus that will help it pick up speed.
This isn’t the first mission to study the sun. NASA has launched several, including the ongoing Solar Dynamics Observatory and the Solar and Heliospheric Observatory.
Two other spacecraft have had close flybys, though not nearly as close as the Parker Solar Probe’s route. In 1974, Helios 1 passed within 45 million kilometres of the sun’s surface, and Helios 2 within 43.4 million kilometres two years later.
“We’ve done so much science by looking at the star. We’ve looked at it every single different way you can imagine. We’ve looked at it in every wavelength, we’ve travelled in beyond the orbit of Mercury even,” Fox said.
“But we need to get into this action region. Into this region where all these mysteries are really occurring. And that’s why we’re doing this kind of daring journey.”