Larry Klaes (email@example.com)
Thu, 22 Jul 1999 16:38:15 -0400
>X-Authentication-Warning: brickbat12.mindspring.com: majordom set sender
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>Date: Thu, 22 Jul 1999 19:36:50 GMT
>From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>Subject: [ASTRO] Asteroid Found By Spacewatch Is Fastest Spinning Solar
>Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
>Asteroid Found By Spacewatch Is Fastest Spinning Solar System Object
>University of Arizona News Services
>July 22, 1999
>James V. Scotti
>(Editors note: Scotti is observing on Spacewatch. He will be back on campus
>Friday, July 23.)
>TUCSON, Ariz. -- A unique near-Earth asteroid discovered last year by
>Spacewatch at the Univerity of Arizona in Tucson is the fastest-spinning
>solar system object yet found, scientists report in tomorrow's issue (July
>23) of Science.
>Only 30 meters (100 feet) across, asteroid 1998 KY26 spins once every 10.7
>minutes. That's 10 times faster than the spin rate of any other object and
>almost 60 times faster than the average of all known asteroid rotation
>periods, the scientists say.
>Whirling at that speed and given its size, 1998 KY26 has to be a strong,
>single chunk of rock that was sent reeling from its parent asteroid in some
>space collision, said James V. Scotti , a senior research specialist at the
>UA Lunar and Planetary Laboratory (LPL) and a co-author of the Science
>LPL Professor Tom Gehrels, Spacewatch co-founder, discovered asteroid 1998
>KY26 on May 28, 1998, using the 0.9 meter (36-inch) Spacewatch telescope at
>Kitt Peak, Ariz. Six nights later Scotti, joined at the Spacewatch
>telescope by Dan Durda, took 111 images of the asteroid, measuring its
>minimum to maximum changes in brightness. Durda of the Southwest Research
>Institute in Boulder, Co., was formerly with LPL.
>Astronomers at telescopes in the Czech Republic, Hawaii and California also
>made the same kind of photometric measurements from June 2 to 8. This was
>when the asteroid made its closest swing by Earth at a half million miles,
>or twice the distance between the Earth and the moon. Between June 6 and 8,
>Steven J. Ostro headed a team from the NASA Jet Propulsion Laboratory in
>Pasadena, Calif., that used the Goldstone X- band radar of NASA's Deep
>Space Network to track the asteroid. Radar echoes revealed the asteroid's
>rapid spin rate. Petr Pravec of Ondrejov Astronomy Institute in the Czech
>Republic combined data gathered by the different optical observing groups
>and constructed a light curve to determine the precise rotation rate.
>The astronomers discovered the size and shape of 1998 KY26 from the radar
>echoes. This asteroid is unusual in that it is almost spherical, with a
>bare-rock surface pocked at least in part by meteoroid bombardment, they
>report. Their optical and radar observations show this asteroid is similar
>to carbonaceous chondritic meteorites, objects that formed early in solar
>system history. These meteorites are rich in primordial complex organic
>compounds and water.
>Asteroids in the 30-meter-diameter range survive between 10 million and 100
>million years before being destroyed in space collisions. Carbonaceous
>chondrites are weaker meteorites, so this asteroid will be smashed sooner
>than later, they add.
>Information from recent asteroid flybys suggests that large asteroids are
>less dense than the meteorites recovered and measured on Earth. Scientists
>theorize that most larger asteroids are porous "rubble piles" rather than
>monolithic bodies, Scotti said. Current theory says that "these rubble
>piles are conglomerates of debris broken apart by multiple collisions and
>held together by their mutual gravity, spinning slowly enough so that they
>don't fall apart," he added.
>Studying the detailed structure of these asteroids involves more than just
>scientific curiosity, Scotti said. There are two practical reasons for
>learning more about them: Asteroid minerals can provide raw materials for
>future space construction, and knowing how asteroids are put together
>provides critical knowledge for deflecting large ones headed for Earth.
>Each month, Spacewatch - the world's first telescope dedicated to searching
>for near-Earth asteroids - finds an average of two-to-three asteroids in
>our vicinity, and another 2,000 new ones in the asteroid belt. Spacewatch
>is funded by NASA, the University of Arizona and private donors.
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