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Space weather

How radiation from the Sun and supernovae poses a constant threat to life on our planet

Our universe can seem like a somewhat benign place, but phenomena in our Solar System and beyond can have a serious impact on life on Earth. Eruptions from the Sun and cosmic rays from afar can cause havoc with our atmosphere, affecting not just satellites and astronauts in orbit but life on Earth too. Over the years we’ve been getting better at predicting space weather, but the risk to Earth is ever present. So we can never be too prepared for the next big event that heads our way.

Space weather refers to a lot of things, although it often relates mostly to the Sun, which has the most direct effect on Earth. While our star happily burns away and provides us with both light and heat, it can on occasion erupt in a violent explosion. One such event is a solar flare, when a build-up of magnetic energy is released. These normally erupt from sunspots, which are dark and relatively cool regions on the Sun’s surface. Flares are exceptionally bright, releasing large amounts of photons and other particles in our direction, and they can last from minutes to hours. They are categorised in a variety of classes, with the most powerful being X-class flares.

Another type of eruption from the Sun is a coronal mass ejection (CME). These are sometimes associated with solar flares, although the exact relationship is unknown. CMEs, like solar flares, are also the result of magnetic fields building up, but they instead hurl large amounts of matter into space. They can look like large fans of gas zooming out, with the hot plasma they produce taking up to three days to reach us. Using telescopes we can see and monitor both solar flares and CMEs before they reach Earth…

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Extract from Space Weather by Jonathan O’Callaghan. Featured in How It Works 112.

Title image credit: NASA

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