It's dangerous out there.
Particles and radiation from the Sun could sicken or kill astronauts en route to Mars or other remote targets. And so could particles from beyond the Sun. In fact, over the last few years, more of these particles have been charging into the solar system than at any other time since the start of the Space Age.
The particles are known as cosmic rays. Most of them are protons -- the electrically charged particles in the hearts of atoms. They're blasted into space at close to the speed of light by exploding stars.
The Sun generates a strong and wide-spread magnetic field that prevents most cosmic rays from entering the solar system.
Over the last few years, though, the Sun has been unusually quiet, so its magnetic field hasn't been as strong or as broad. According to a study released last year, that's allowed more cosmic rays to penetrate all the way to the inner solar system.
Unlike the intense outbursts from the Sun, which can kill in a hurry, cosmic rays are slow killers -- they can damage enough cells to cause cancer and other health problems.
The Sun is getting more active right now, so the number of cosmic rays should be going down. But studies show that a few centuries ago, the cosmic rays were flying much thicker. That means that astronauts on long-range flights through the solar system will need good shielding to protect them from the dangers of outer space. More about that tomorrow.
Script by Damond Benningfield, Copyright 2010
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