For the first time, a space probe has succeeded in flying through the sun’s outer atmosphere, known as the corona. The probe was launched in 2018, is about the size of a small car and can withstand more heat and radiation than any missile before. The Swiss Thomas Zurbuchen is Director of Science at NASA and explains the importance of this mission in an interview.
SRF News: Why is this NASA mission a milestone?
Thomas Zurbuchen: It is an unbelievable success to get so close to the sun on a mission. We have looked at the sun for over 50 years, the most important star for us, which gives us life here on earth. For the first time we touched the sun, solar material that hovers in the sky above the sun and is held down by magnetic fields.
Scientifically, one of the most important questions is how the stars heat the surface.
What exactly did the probe do in the solar atmosphere?
The probe is on an orbit going out to Venus and getting closer and closer to the sun. You can think of it like a football field: the goal on one side is the sun, the goal on the other side is the earth. We are now halfway in the penalty area near the sun. There we make precise observations of the environment.
If you stand very close to the fire while grilling, your head will be warm. But as soon as you walk away from the fire, your head suddenly becomes 100 times hotter. We have this situation with the sun.
They hope to gain knowledge about the stars so that we can better understand how they work. What are the specific questions?
Scientifically, one of the most important questions in star physics is how the stars heat the surface. When we look at the sun with a telescope, the sun looks like an oil pan on the surface. The interior of the sun is heated by nuclear fusion and the material comes to the surface. If you walk away from the sun or other stars, the sun’s atmosphere becomes a lot hotter than on the surface. If you say that the surface is around 10,000 degrees, the atmosphere above it is 1,000,000 degrees. This is incredibly difficult to understand. If you stand very close to the fire while grilling, your head will be warm. But as soon as you walk away from the fire, your head would suddenly become 100 times hotter. We have this situation with the sun.
Why is it important for us on earth to understand why the surface of the sun is less hot than the atmosphere?
The hot atmosphere has an incredible impact on us. First, this atmosphere heats the upper layer of the earth, so it has an impact on the end of our atmosphere through ultraviolet radiation. All of the unhealthy ultraviolet radiation that sometimes hits the earth comes from there. Second, magnetic storms can be located. These storms have a negative impact on our satellites, which we need for communication or GPS, for example. And just like on earth, where we make weather forecasts, we want to be able to make predictions about the weather in space, the so-called space weather.
As with Icarus, is there a risk that the probe will get too hot and burn up?
We built the probe so that this would not happen. But of course: everything has to go perfectly on each of these fly-bys. The probe must be placed in such a way that the heat shield is aimed at the sun. If there was a mistake here, the mission would have failed within minutes and the probe burned up.
The interview was conducted by Simone Hulliger.