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This series of Hubble Space Telescope
images reveals the breakup of an asteroid over a period of several
months starting in late 2013. The largest fragments are up to 180
meters (200 yards) in radius.
Image Credit: NASA, ESA, D. Jewitt
(UCLA)
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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.
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 mph. The
asteroid began coming apart early last year, but new pieces continue
to reveal themselves, as proved in the most recent images.
It is unlikely the asteroid is
disintegrating because of a collision with another asteroid, which
would have been instantaneous and violent by comparison to what has
been observed. Debris from such a high-velocity smashup would also be
expected to travel much faster than observed. Nor is the asteroid
coming unglued due to the pressure of interior ices warming and
vaporizing.
This leaves a scenario in which the
asteroid is disintegrating due to a subtle effect of sunlight, which
causes the rotation rate of the asteroid to gradually increase.
Eventually, its component pieces—like grapes on a stem—succumb to
centrifugal force and 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, P/2013 R3
must have a weak, fractured interior—probably as the result of
numerous non-destructive collisions with other asteroids. Most small
asteroids are thought to have been severely damaged in this way.
P/2013 R3 is likely the byproduct of just such a collision sometime
in the last billion years.
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 Hubble Space Telescope is a project
of international cooperation between NASA and the European Space
Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages
the telescope. The Space Telescope Science Institute (STScI) in
Baltimore conducts Hubble science operations. STScI is operated for
NASA by the Association of Universities for Research in Astronomy,
Inc., in Washington.
J.D. Harrington
Headquarters, Washington
202-358-5241
j.d.harrington@nasa.gov
Ray Villard
Space Science Telescope Institute,
Baltimore, Md.
410-338-4493 / 410-338-4514
Villard@stsci.edu
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