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
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