An asteroid some 300 million miles from the Sun broke up slowly before astronomers' eyes this week, probably after being weakened by collisions with other space objects.

"Seeing this rock fall apart before our eyes is pretty amazing," lead investigator David Jewitt, a professor in the University of California Los Angeles Department of Earth, Planetary and Space Sciences, told the AFP.

The occurrence was unusual in that the asteroid wasn't suddenly broken up by a major collision or by going too close to the Sun. Asteroid P/2013 R3 was pulled apart slowly "like grapes on a stem" as sunlight caused it to rotate faster and faster, Jewitt told the AFP.

The Hubble Space Telescope captured images of the process, which unfolded at a rate slower than human walking speed, according to the Los Angeles Times.

In a press release, UCLA described the asteroid pieces as "drifting away from each other at a leisurely pace of one mile per hour, slower than a strolling human."

Astronomers had been watching the asteroid since September and believe it began coming apart early last year.

"Seeing this rock fall apart before our eyes is pretty amazing," Jewitt described in the press release.

Because the pieces were moving away from each other so gradually, scientists knew the asteroid wasn't breaking up due to a recent impact, which would have immediately sent pieces flying.

Coming apart in around 10 fragments, the asteroid is now in pieces that weigh as much as 200,000 tons each, the four largest each measuring twice the size of a football field.

The fragments will further disintegrate into meteoroids, and many of them will go into the Sun. 

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