Our solar system is an active place, and that is no better illustrated than with these recent observations by the Hubble Space Telescope of asteroid P/2013 R3 breaking apart — and it’s not even disintegrating in Earth’s or any other planet’s atmosphere, but rather as it travels through space 480 million km away from the Sun!
Seen over the course of four months, the breakup of the 200,000-ton space rock is thought to not be the result of an impact event but rather the slight but unyielding force of solar illumination on an already compromised cluster of rubble, barely held together by its own gravity.
“This is a really bizarre thing to observe — we’ve never seen anything like it before,” says co-author Jessica Agarwal of the Max Planck Institute for Solar System Research, Germany. “The break-up could have many different causes, but the Hubble observations are detailed enough that we can actually pinpoint the process responsible.”
Unlike previous breakups observed in the asteroid belt, this is a fairly slow-motion process. The pieces of P/2013 R3 are moving away from each other at a relative 1.5 km/hour — about as fast as a person walking.
If an impact were responsible, fragments would be expected to be traveling much faster and in all sorts of different directions. That’s why astronomers suspect solar radiation.
But it’s not thought that the Sun’s heat has somehow ‘melted’ the asteroid apart, but rather that the physical reaction of the asteroid itself unevenly radiating absorbed heat has altered its rotation over time — enough so that centrifugal forces overcome its inward gravitational pull and it’s literally pulled apart by the resulting shear. (Otherwise known as the Yarkovsky–O’Keefe–Radzievskii–Paddack, or YORP, effect.)
This is the first time this recently-hypothesized process has been directly observed occurring in the asteroid belt.
“This is a rock. Seeing it fall apart before our eyes is pretty amazing.”
– David Jewitt of UCLA, lead author of the study
Eventually fragments of this asteroid may one day find their way to Earth, burning up as bright meteors in our night sky.