(Image: NASA, ESA, and D. Jewitt (UCLA))

Lengthy break-ups are complicated, even if you’re an asteroid. The Hubble Space Telescope has spotted a space rock going its separate ways – the first ever caught in the act. This animation shows it disintegrating in a series of images taken between October 2013 and January this year.

Why couldn’t it stick together? Comets are icy and liable to break up when they get too close to the sun, as happened to comet ISON last year, but rocky asteroids usually fragment after a collision with another object, so we think.

This asteroid, known as P/2013 R3, is drifting apart much too slowly for that, with its 10 or so fragments separating at the leisurely pace of 1.5 kilometres per hour. One idea is that the true cause was something much less dramatic than a collision: the constant heat of the sun. If the asteroid had been weakened by previous impacts, the heating could have produced a small force on one side of the rock, making it rotate. This extra spin could have been enough to make it fly apart, producing comet-like tails.

It’s not the first time Hubble has seen a freaky asteroid. In September last year astronomers used it to observe an object called P/2013 P5, and realised that it has six tails. That was probably falling apart in a sun-induced spin as well, but the slightly newer P/2013 R3 is the first to have its fragments caught on camera.