The incredibly rare sight of an asteroid’s disintegration was recently captured in a series of images by NASA’s Hubble Space Telescope. The images show (in great clarity) the never-before-seen process of a fully intact asteroid coming apart — into ten pieces in this instance.
While fragile comet nuclei have been observed disintegrating during close approaches to the Sun, this is something quite different.
“This is a rock. Seeing it fall apart before our eyes is pretty amazing,” explained David Jewitt of UCLA, USA, who led the astronomical forensics investigation.
The disintegrating asteroid, dubbed P/2013 R3, was first observed as a rather unusual, blurry-looking object on September 15th 2013, by the Catalina and Pan-STARRS sky surveys. “Follow-up observations on 1 October with the Keck Telescope on Mauna Kea, Hawaii, revealed three co-moving bodies embedded in a dusty envelope that is nearly the diameter of Earth.”
“Keck showed us that this thing was worth looking at with Hubble,” Jewitt stated. “With its superior resolution, the space-based Hubble observations soon showed that there were really ten distinct objects, each with comet-like dust tails. The four largest rocky fragments are up to 200 metres in radius, about twice the length of a football pitch.”
The data from Hubble showed that the individual fragments are diverging from each other at a rate of around 1.5 kilometers per hour — that’s slower than the average person walks. While the asteroid began disintegrating sometime early last year, the most recent observations show that new pieces are still continuing to emerge.
“This is a really bizarre thing to observe — we’ve never seen anything like it before,” stated 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.”
NASA/ESA/Hubble Space Telescope provides more:
The ongoing discovery of more fragments makes it unlikely that the asteroid is disintegrating due to a collision with another asteroid, which would be instantaneous and violent in comparison to what has been observed. Some of the debris from such a high-velocity smash-up would also be expected to travel much faster than has been observed.
It is also unlikely that the asteroid is breaking apart due to the pressure of interior ices warming and vaporising. The object is too cold for ices to significantly sublimate, and it has presumably maintained its nearly 480-million-kilometre distance from the Sun for much of the age of the Solar System.
This leaves a scenario in which the asteroid is disintegrating due to a subtle effect of sunlight that causes the rotation rate to slowly increase over time. Eventually, its component pieces gently pull apart due to centrifugal force. The possibility of disruption by this phenomenon — known as the YORP effect — has been discussed by scientists for several years but, so far, never reliably observed (eso1405).
For break-up to occur, P/2013 R3 must have a weak, fractured interior, probably the result of numerous ancient and non-destructive collisions with other asteroids. Most small asteroids are thought to have been severely damaged in this way, giving them a “rubble pile” internal structure. P/2013 R3 itself is probably the product of collisional shattering of a bigger body some time in the last billion years.
“This is the latest in a line of weird asteroid discoveries, including the active asteroid P/2013 P5, which we found to be spouting six tails,” stated Agarwal. “This indicates that the Sun may play a large role in disintegrating these small Solar System bodies, by putting pressure on them via sunlight.”
The findings were published in the Astrophysical Journal Letters on March 6th 2014.
Image Credit: NASA, ESA, D. Jewitt (UCLA)