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X-Ray Astronomy IV

January 10, 2018

Little stars can pack a wallop. They can produce giant explosions of radiation and charged particles. And that could be bad news for the prospects for life on planets around such stars.

The smallest true stars are red dwarfs. They can be as little as just eight percent the mass of the Sun. Such stars are small, cool, and faint — only about one ten-thousandth as bright as the Sun.

The stars are quite turbulent. Giant bubbles of gas rise from such a star’s core to the surface, where they cool and sink. This generates powerful magnetic fields. The field lines sometimes tangle and snap, producing outbursts known as flares. The most powerful flares are far more energetic than those produced by the Sun.

Any planets in the “habitable zone” of such a star would be quite close to the star itself. So a flare would wash the planet’s surface with radiation — especially ultraviolet and X-rays. In fact, a red-dwarf flare can produce more X-rays than the entire Sun does. So while red dwarfs are puny, they can shine as some of the brightest X-ray objects in the sky.

Repeated flares could destroy a planet’s ozone layer, and even strip away its atmosphere. That would leave any life on the planet unprotected.

We don’t know what form life might take on other worlds, though, or whether life might exist underground. But we do know that life would be difficult around these tiny stars with giant kicks.

More about X-ray astronomy tomorrow.

Script by Damond Benningfield

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