I'm obsessed with the apocalypse. No joke.

I always carry a mini-emergency kit stuffed in an Altoids tin, and I know that if the apocalypse comes, my husband and I are supposed to meet at our apartment, grab our pre-packed bags, maybe the cat, and head for the hills. 

We own a Grundig self-powered radio with hand crank and charger for cell phones with various adapters. Survival manuals. Canned food. Bottled water. Check. Check. Check.

Zombies, watch out! We're armed. Nuclear attack? No prob--we've got pills for that.

But what if the apocalypse isn't zombies? What if it's not radiation poisoning we've got to be worried about? What if it's simply some giant celestial object bearing down on us?--I'd need several pills to handle that. 

Sounds improbable? Think again.

Illustration by LYNETTE R COOK

PLANET TO PLANET, DUST TO DUST

According to astronomers at UCLA, Tennessee State University and the California Institute of Technology, two terrestrial planets collided some 300 light-years from Earth, leaving an immense ring of dust surround its mature sun-like star.

"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 co-author Gregory Henry, an astronomer at Tennessee State University (TSU). "A massive disk of infrared-emitting dust circling the star provides silent testimony to this sad fate."

"It's as if Earth and Venus collided with each other," said Benjamin Zuckerman, UCLA professor of physics and astronomy and a co-author on the paper.

"Astronomers have never seen anything like this before."

Actually, even they didn't see the planetary collision because it happened sometime in the past few hundred thousand years, a recent occurrence in the scope of the universe. 

The collision wasn't observed directly, but inferred by the massive amount of dust particles orbiting BD+20 307, a close binary star (two stars orbiting around their common center of mass) located in the constellation Aries.

The two stars are very similar in mass, temperature and size to our own sun, except BD-2 307 is surrounded by one million times more dust than is orbiting our sun. That's more warm orbiting dust than any other sun-like star known to astronomers. 

Zuckerman, Henry, and Michael Muno, an astronomer at Caltech at the time of the research, studied BD-2 307, gathering X-ray data using the Chandra X-ray Observatory, a NASA launched satellite, and brightness data from one of TSU's automated telescopes in southern Arizona, hoping to discover the age of the star. 

Muno explained that early on in their research, they "expected to find that BD-2 307 was relatively young, a few hundred million years old at most." The massive dust ring surrounding the star suggested that it was in its final stages in the formation of the star's planetary system. 

However, astronomers Francis Fekel and Michael Williamson, also from TSU, provided additional spectroscopic data from another TSU automated telescope in Arizona, confirming that BD-2 307 was actually much older than originally thought. 

"The binary system appears to have an age of several billion years, comparable to our solar system," Fekel said. 

Apparently, the dust surrounding BD-2 307 orbits the binary system very closely, where dust typically cannot survive long. Large pieces are reduced to dust, and small pieces are pushed away by stellar radiation. Therefore, the dust-forming collision near BD-2 307 must have taken place rather recently. 

This sad tale of planetary demise has astronomers like Fekel wondering, "How do planetary orbits become destabilized in such an old, mature system, and could such a collision happen in our own solar system?"

SHOULD WE HEAD FOR THE HILLS?

Those fearing a celestial apocalypse can sleep a little more soundly with the knowledge that computer models predicting planetary motions, find a "small probability for collisions of Mercury with Earth or Venus sometime in the next billion years or more."

No word was mentioned of Mars. 

However, Zuckerman points out that major collisions have already occurred in our own backyard. Indeed, many astronomers believe our moon was formed from the grazing collision of two planets--the young Earth and a body about the size of Mars. The crash would have created vast amounts of debris, some of which condensed to form our favorite celestial nightlight. 

According to Zuckerman, the planetary collision in the BD-2 307 system puts Earth's collision with an asteroid, 65 million years ago, to shame. By comparison, he calls Earth's collision, "a mere pipsqueak."

That's the asteroid collision that many believe killed the dinosaurs. 

I think I'll still carry my emergency kit with me. But I'll leave the Hazmat suit at home. 

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The findings will be published in a December issue of the Astrophysical Journal.