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What are the biggest unsolved mysteries about the Sun?

The Sun is the most well studied star in the Universe for us on Earth, and many of the theories about how stars evolve are based on our ability to observe the Sun in exceptional detail. The biggest unsolved problem now is how to explain, understand, and predict the activity that produces the hot corona, the cycle of sunspots, and the related dynamic phenomena that we know as coronal mass ejections and flares.

Stars don’t last forever. How long is ours likely to last, and what will happen when it dies?

In several billion years its outer layers will start to swell, making it a giant star that has expanded to include the orbit of Mercury. But our descendants should have mastered space travel by then. Before that time, the Andromeda Galaxy will collide with our own Milky Way, so perhaps the gravitational interaction will throw stars around.

What are solar winds, and how damaging can they be to life on Earth?

The solar corona is so hot that the Sun’s strong gravity cannot fully contain it, and the result is a flow of particles from the Sun known as the solar wind. Our atmosphere and our magnetic field protect us from most of the damaging effects, but satellites and astronauts in space – and even passengers on over-the-pole flights – can be vulnerable, and constant surveillance of the Sun is needed for their protection.

LEON GOLUB is a Senior Astrophysicist at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts