New, temporary radiation belt spotted around Earth

You may not have noticed it, but for several weeks last year, the Earth was surrounded by an extra ring of radiation.

There are two doughnut-shaped rings of highly charged particles encircling the planet. Discovered in 1958, they're known as the Van Allen radiation belts.

So it came as a surprise when NASA's recently launched twin satellites to the treacherous region discovered a third, temporary ring. It appeared for a month before a shock wave from the sun destroyed it. Scientists are still trying to figure out how often this happens.

The twin spacecraft launched last year on a mission to explore the Van Allen belts. Solar storms can cause the rings to expand, posing a potential threat to satellites.

The discovery was reported online Thursday in the journal Science.