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Space rock mysteriously falls apart

March 6, 2014
Courtesy of NASA
and World Science staff

NASA’s Hub­ble Space Tel­e­scope has recorded the nev­er-be­fore-seen break-up of an as­ter­oid in­to as many as 10 smaller pieces, as­tro­no­mers re­port.

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.

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


“This is a rock, and see­ing it fall apart be­fore our eyes is pret­ty amaz­ing,” said Da­vid Je­witt of the Uni­vers­ity of Cal­i­for­nia at Los An­ge­les, who led the as­tro­nom­i­cal fo­ren­sics in­ves­ti­ga­t­ion.

The crum­bling as­ter­oid, des­ig­nat­ed P/2013 R3, was first no­ticed as an un­usu­al, fuzzy-look­ing ob­ject by the Catalina and Pa­n STARRS sky sur­veys on Sept. 15. 

A fol­low-up ob­serva­t­ion on Oc­to­ber 1 with the W. M. Keck Ob­serv­a­to­ry on the sum­mit of Mauna Kea, a dor­mant vol­ca­no on the is­land of Ha­waii, re­vealed three bod­ies mov­ing to­geth­er in an en­ve­lope of dust nearly the di­am­e­ter of Earth.

“The Keck Ob­serv­a­to­ry showed us this thing was worth look­ing at with Hub­ble,” Je­witt said. “With its su­pe­ri­or res­o­lu­tion, space tel­e­scope ob­serva­t­ions soon showed there were really 10 em­bed­ded ob­jects, each with comet-like dust tails. The four larg­est rocky frag­ments are up to 400 yards in di­am­e­ter, about four times the length of a foot­ball field.”

Hub­ble da­ta showed the frag­ments drift­ing away from each oth­er at a lei­surely one mile per hour, like a slowly walk­ing pe­rson. The as­ter­oid be­gan com­ing apart early last year, but new pieces con­tin­ue to re­veal them­selves, as the new­est im­ages show.

It’s un­likely the as­ter­oid is dis­in­te­grat­ing be­cause of a col­li­sion with anoth­er as­ter­oid, which would have been in­stan­ta­ne­ous and vi­o­lent, re­search­ers said. Nor is the as­ter­oid com­ing un­glued due to the pres­sure of in­te­ri­or ices warm­ing and va­por­iz­ing.

This leaves a sce­nar­i­o, as­tro­no­mers said, in which it is dis­in­te­grat­ing due to a sub­tle ef­fect of sun­light, which causes the as­ter­oid’s spin rate to grad­u­ally in­crease so that its pieces gently pull apart. The pos­si­bil­ity of dis­rup­tion in this man­ner has been dis­cussed by sci­en­tists for sev­eral years, but nev­er re­liably ob­served.

For this sce­nar­i­o to oc­cur, the as­ter­oid must have a weak, frac­tured in­te­ri­or—probably as the re­sult of pre­vi­ous col­li­sions, the sci­en­tists added. Most small as­ter­oids are thought to have been dam­aged in this way.

With the pre­vi­ous dis­cov­ery of an ac­tive as­ter­oid spout­ing six tails, named P/2013 P5, as­tro­no­mers are find­ing more ev­i­dence the pres­sure of sun­light may be the pri­ma­ry force caus­ing the dis­in­tegra­t­ion of small as­ter­oids—less than a mile across-- in our so­lar sys­tem.

The as­ter­oid’s rem­nant de­bris, weigh­ing about 200,000 tons, will in the fu­ture pro­vide a rich source of me­te­oroids. Most will even­tu­ally plunge in­to the sun, but a small frac­tion of the de­bris may one day blaze across our skies as me­te­ors, the re­search­ers said.


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NASA’s Hubble Space Telescope has recorded the never-before-seen break-up of an asteroid into as many as 10 smaller pieces, astronomers report. 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. “This is a rock, and seeing it fall apart before our eyes is pretty amazing,” said David Jewitt of the University of California at Los Angeles, who led the astronomical forensics investigation. The crumbling asteroid, designated P/2013 R3, was first noticed as an unusual, fuzzy-looking object by the Catalina and Pan STARRS sky surveys on Sept. 15, 2013. A follow-up observation on October 1 with the W. M. Keck Observatory on the summit of Mauna Kea, a dormant volcano on the island of Hawaii, revealed three bodies moving together in an envelope of dust nearly the diameter of Earth. “The Keck Observatory showed us this thing was worth looking at with Hubble,” Jewitt said. “With its superior resolution, space telescope observations soon showed there were really 10 embedded objects, each with comet-like dust tails. The four largest rocky fragments are up to 400 yards in diameter, about four times the length of a football field.” Hubble data showed the fragments drifting away from each other at a leisurely one mile per hour, like a slowly walking person. The asteroid began coming apart early last year, but new pieces continue to reveal themselves, as the newest images show. It’s unlikely the asteroid is disintegrating because of a collision with another asteroid, which would have been instantaneous and violent, researchers said. Nor is the asteroid coming unglued due to the pressure of interior ices warming and vaporizing. This leaves a scenario, astronomers said, in which it is disintegrating due to a subtle effect of sunlight, which causes the asteroid’s spin rate to gradually increase so that its pieces gently pull apart. The possibility of disruption in this manner has been discussed by scientists for several years, but never reliably observed. For this scenario to occur, the asteroid must have a weak, fractured interior—probably as the result of previous collisions, the scientists added. Most small asteroids are thought to have been damaged in this way. With the previous discovery of an active asteroid spouting six tails, named P/2013 P5, astronomers are finding more evidence the pressure of sunlight may be the primary force causing the disintegration of small asteroids—less than a mile across-- in our solar system. The asteroid’s remnant debris, weighing about 200,000 tons, will in the future provide a rich source of meteoroids. Most will eventually plunge into the sun, but a small fraction of the debris may one day blaze across our skies as meteors, the researchers said.