[meteorite-list] Worlds in Collision

[Sean T. Murray]

Great picture for this on APOD:
http://antwrp.gsfc.nasa.gov/apod/astropix.html

----- Original Message ----- 
From: "Darren Garrison" <cynapse at charter.net>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Thursday, September 25, 2008 1:04 AM
Subject: [meteorite-list] Worlds in Collision


http://www.foxnews.com/story/0,2933,427023,00.html

Huge Planetary Collision Left Tons of Space Debris

Around a distant star, two planets similar to Earth collided and were 
destroyed,
astronomers said today.

The somewhat speculative scenario is based on the leftovers: a ring of 
debris
around the star that includes a million times more dust than now circles our
sun.

"It's as if Earth and Venus collided," said researcher Benjamin Zuckerman, 
UCLA
professor of physics and astronomy. "Astronomers have never seen anything 
like
this before. Apparently, major catastrophic collisions can take place in a 
fully
mature planetary system."

The researchers used X-ray data and other observations of a star called 
BD+20
307. They had assumed it was a young star, just a few hundred million years 
old,
and the debris was leftovers from planet formation.

But earlier this year, another study showed the star was actually a binary 
pair,
and that the stars were billions of years old.

So why all the debris? The dust is about the same distance from the stellar 
pair
as Earth is from the sun, and given current theories of planet formation, 
that
debris should have been swept up into planets by now or pushed away by 
stellar
radiation. It simply shouldn't be there.

A colossal collision must have created all that dust sometime in the past 
few
hundred thousand years and perhaps much more recently, the astronomers 
figure.

It would have been a whopper.

"If any life was present on either planet, the massive collision would have
wiped out everything in a matter of minutes - the ultimate extinction 
event,"
said Gregory Henry, an astronomer at Tennessee State University (TSU) who 
worked
with Zuckerman on the research. "A massive disk of infrared-emitting dust
circling the star provides silent testimony to this sad fate."

To put the collision into context, Zuckerman said: "By contrast with the 
massive
crash in the BD+20 307 system, the collision of an asteroid with Earth 65
million years ago, the most favored explanation for the final demise of the
dinosaurs, was a mere pipsqueak."

The work was funded by the National Science Foundation and NASA, and also by 
TSU
and the State of Tennessee. It will be detailed in the December issue of the
Astrophysical Journal.

The conclusion has the astronomers thinking about home.

"This poses two very interesting questions," said TSU astronomer Francis 
Fekel.
"How do planetary orbits become destabilized in such an old, mature system, 
and
could such a collision happen in our own solar system?"

It has already happened here, in fact. Our moon is thought to have been 
created
when a Mars-sized object slammed into Earth.

Henry points out that computer models done by other researchers suggest that 
as
planets in our solar system migrate over time, there is a "small probability 
for
collisions of Mercury with Earth or Venus sometime in the next billion years 
or
more."

Of course by then the sun will have expanded and we might be toast anyway.
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