Title: Anatomy of an Asteroid Break-Up: The Case of P/2013 R3 Author: Dave Jewitt, Jessica Agarwal, Jing Li, Harold Weaver, Max Mutchler, Stephen Larson
We present an analysis of new and published data on P/2013 R3, the first asteroid detected while disintegrating. Thirteen discrete components are measured in the interval between UT 2013 October 01 and 2014 February 13. We determine a mean, pair-wise velocity dispersion amongst these components of Delta v=0.33±0.03 m s^-1 and find that their separation times are staggered over an interval of ~5 months. Dust enveloping the system has, in the first observations, a cross-section ~30 km² but fades monotonically at a rate consistent with the action of radiation pressure sweeping. The individual components exhibit comet-like morphologies and also fade except where secondary fragmentation is accompanied by the release of additional dust. We find only upper limits to the radii of any embedded solid nuclei, typically ~100 to 200 m (geometric albedo 0.05 assumed). Combined, the components of P/2013 R3 would form a single spherical body with radius \lesssim 400 m, which is our best estimate of the size of the precursor object. The observations are consistent with rotational disruption of a weak (cohesive strength ~50 to 100 N m^-2) parent body, ~400 m in radius. Estimated radiation (YORP) spin-up times of this parent are \lesssim 1 Myr, shorter than the collisional lifetime. If present, water ice sublimating at as little as 10^-3 kg s^-1 could generate a torque on the parent body rivaling the YORP torque. Under conservative assumptions about the frequency of similar disruptions, the inferred asteroid debris production rate is \gtrsim 10³ kg s^-1, which is at least 4% of the rate needed to maintain the Zodiacal Cloud.
NASA's Hubble Space Telescope has recorded the never-before-seen break-up of an asteroid into as many as 10 smaller pieces. Fragile comets, comprised of ice and dust, have been seen falling apart as they near the sun, but nothing like this has ever before been observed in the asteroid belt. Read more
Astronomers Puzzle Over Newfound Asteroid That Acts Like a Comet
The main-belt comet, designated P/2013 R3, was discovered in September at two observatories: the Catalina Sky Survey in Arizona and the Pan-STARRS 1 telescope in Hawaii. Only a dozen or so main-belt comets have been discovered, so astronomers quickly took to the world's largest telescopes to get a better look at the rare object. Jewitt examined P/2013 R3 with the 10-meter Keck 1 telescope in Hawaii, whereas astrophysicist Javier Licandro of the Institute of Astrophysics of the Canary Islands and his colleagues used the institution's 10.4-meter Gran Telescopio Canarias. Both saw that the object was different than all other main-belt comets discovered so far. Read more