Astronomers once thought asteroids were boring, wayward space rocks that simply orbit around the Sun. These objects were dramatically presented only in science fiction movies.

But recent observations show that asteroids are anything but dull. In reality they are dynamic, active worlds that can ultimately disintegrate due to the long-term subtle effects of sunlight, which can slowly spin them up until they begin to shed material.

Several telescopes, including NASA's Hubble Space Telescope, have caught the gradual self-destruction of the asteroid (6478) Gault. Images from Hubble show two narrow, comet-like tails of dusty debris streaming from the diminutive asteroid.

For Gault, a mass of rubble a few miles across, mere sunlight set the stage for its gradual demise. The force of sunlight, in concert with Gault's own asymmetrical shape, speeded up the asteroid's rotation over a period of more than 100 million years. The estimated spin-up rate is 1 second every 10,000 years.

Today, the asteroid is rotating once every two hours, a speed so fast that it can no longer hold its surface material. The slightest disturbance — perhaps the impact of a pebble, or just a failure of the stressed material — may have set off a collapse. The dust left the asteroid's surface in gentle, short bursts, perhaps due to landslides lasting anywhere from a few hours to a few days. The particles are drifting away from Gault's surface at the speed of a strolling human. The gentle process is like scattering flour into the air, where wind — or sunlight, in the case of Gault — stretches the debris into a long streamer.

Astronomers will monitor the asteroid for future events. About 800,000 known asteroids reside between Mars and Jupiter, and they may fly apart at the rate of roughly one per year.

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