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jbjb When Worlds Collide you ll see the most amazing, awe inspiring scenes ever put on
film. The forces of nature unleashed in all their terrifying force. Tremendous tidal waves
smashing New York City. Molten fires in the bowels of the earth gushing out to consume
our world. Nearly 60 years ago, audiences thrilled to the destruction of the Earth in
George Pal s classic film, When Worlds Collide. The idea of a planetary smash-up is a staple
of science fiction, but can it really happen? Astronomers using NASA s Spitzer Space Telescope
think they ve actually seen the aftermath of such a collision around another star. The
story unfolded as Dr. Casey Lisse and his team studied disks around young stars. Once
planets have formed astronomers think there are a lot of left-over asteroids in the system.
They occasionally slam together and produce dusty debris. Spitzer s Infrared Spectrograph was designed to detect
the faint glow from this material. By spreading the light out into its component colors, astronomers
can look for the spectral fingerprints of different minerals. Our dusty star of interest
is a faint speck known as HD 172555. It s about 100 light years away and 12 million
years old which, compared to our 4.5 billion year old Sun, is like a baby born a few days
ago. Studying its spectrum, Dr. Lisse and his colleagues realized they had found something
very peculiar that they had not seen around other stars. Aside from the usual indicators
of rocky rubble, they found features corresponding to tektite, obsidian, and silicon monoxide
gas. What s strange is that tektite and obsidian are formed from molten materials. Tektites
are hardened chunks of lava found around meteor impacts on Earth, and obsidian is volcanic
glass. Vaporized rocks can form silicon monoxide gas. You don t get this kind of material by
just smashing a couple of asteroids together. The evidence suggests something much more
cataclysmic. Imagine what would happen if our moon slammed, at high velocity, into a
Mercury-sized planet. The resulting impact would eject a massive amount of molten material
into space. As it cooled it would likely form tektite, obsidian, and silicon monoxide gas,
explaining the features seen in the HD 172555 spectrum. s amazing to think Spitzer may have
caught the aftermath of such an incredible collision. But, it s not the first time astronomers
have speculated about world-shattering events. In fact, similar things may have happened
right here in our own back yard. Mercury is a strangely dense planet compared to the other
worlds in the solar system. Now if it formed from the same stuff as Venus and Earth, why
would it be any different? A world-shattering impact could be the answer. When planets form
the lighter materials rise and denser ones sink to the core. Remove the outer, lighter
layers and you re left with a denser planet, once what s left cools off. Looking to our
neighbor Mars we see a massive impact scar in its Southern hemisphere. This area, known
as the Hellas Basin, must have formed from an asteroid impact long ago. The resulting
plume of molten material would have been blasted into space, some of it eventually reaching
the ancient Earth. Even closer to home, most astronomers believe that our own moon was
formed in a similar cataclysm. The theory is that a Mars-sized body grazed the still-
forming Earth, generating a massive amount of molten debris. The orbiting rubble would
clump together over time, forming the moon. The tektite and obsidian debris from such
massive impacts would not last long around our sun, or others. Solar winds and gravitational
interactions tend to sweep away the dust over time, and in a few tens of thousands of years
the evidence would be erased. In the long history of our solar system, that s hardly
the blink of any eye. The evidence may be long gone here, but seeing what may happen
when worlds collide around a nearby star shows us it s not just science fiction after all.
For the Spitzer Science Center, I m Dr. Robert Hurt reminding you there s a hidden universe
just waiting to be discovered. When worlds collide, the result is spectacular, and astronomers
think they ve detected the aftermath of such an event around an Thomas Lucas Normal Thomas
Lucas Microsoft Word 10.1 4)*q Thomas Lucas Productions, Inc. When worlds collide, the
result is spectacular, and astronomers think they ve detected the aftermath of such an
event around an Title +chR Microsoft Word Document NB6W Word.Document.8