When Worlds Collide (in Sci-Fi and Science)

From Spitzer Space Telescope’s acclaimed Hidden Universe series, NASA/JPL/Caltech.

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 m