[meteorite-list] UA Catalina Sky Survey Discovers Possible Extinct Comet (596 Scheila)

[Ron Baalke]

http://uanews.org/node/36262

FOR IMMEDIATE RELEASE
FROM THE UNIVERSITY OF ARIZONA

December 23, 2010


Contact information follows this story.

UA Catalina Sky Survey Discovers Possible Extinct Comet

The extraterrestrial rock is tumbling through space alongside 
thousands of similar objects in our solar system's main asteroid 
belt, roughly between the orbits of Mars and Jupiter.

An asteroid discovered more than 100 years ago my not be an 
asteroid at all, but an extinct comet that is coming back to 
life, according to new observations.

The night of Dec. 11, Steve Larson, senior staff scientist with 
the Catalina Sky Survey, was searching for potentially hazardous 
asteroids when he came across what looked like a comet: a faint, 
wispy tail surrounding a bright, star-like core. Four images 
taken over the course of 30 minutes revealed the object was 
moving relative to the background stars.

"Its brightness of a total magnitude of 13.4 visual, which is 
about 900 times fainter than the faintest star you can see in a 
clear, dark sky, led me to suspect that it was a known comet, but 
I checked the comet database and got nothing," Larson said.

According to Larson, comets are thought to be a major source of 
Earth's water, and "extinct" comets may be useful resources for 
space exploration. 

Further investigation revealed that the object was a known 
asteroid called (596) Scheila, discovered in 1906. The 
extraterrestrial rock is tumbling through space alongside 
thousands of similar objects in our solar system's main asteroid 
belt, roughly between the orbits of Mars and Jupiter, out of the 
ecliptic plane in which most planets and asteroids travel.

Catalina Sky Survey team member Alex Gibbs checked previous 
images in the survey's archives but found no activity until Dec. 3. 
At that time, the object appeared brighter and slightly diffuse.

Previous analysis of (596) Scheila's color indicated that it is 
composed of primitive carbonaceous material left over from the 
formation of the solar system and might be an extinct comet.

After the discovery was announced, the astronomical community 
responded by pointing many of the world's largest telescopes at 
the object to obtain images and spectra to determine if its tail 
consists of ice and gases spewing out of the body or if it is 
dust left behind from a collision with another asteroid. 
Preliminary spectra of the outburst show that the coma surrounding 
the asteroid is composed of dust, but more observations will be 
needed to understand just what is happening with (596) Scheila.

"Most asteroids are collision fragments from larger asteroids and 
display a range of mineral composition," Larson explained. "But 
a fraction are thought to be former comets whose volatile ices 
have been driven off by the sun. If the activity in Scheila 
proves to be cometary in nature, this will be only the sixth 
known main-belt comet, and about 100 times larger than 
previously identified main belt comets."

In 1998, Larson founded the Catalina Sky Survey, a NASA-supported 
project to discover and catalog Earth-approaching and potentially 
hazardous asteroids.  It operates two telescopes in the Catalina 
Mountains and one in Australia and is currently discovering 70 
percent of the world's known near-Earth objects, including one 
that fell in northern Sudan in 2008. 

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MEDIA CONTACT:

Steve Larson, Catalina Sky Survey, (520) 621-4973, 
slarson at lpl.arizona.edu