Invaders from outer space might have doomed the dinosaurs, after all. Dr. Daniel Whitmire, a retired professor of astrophysics, published a paper that a recently inferred ninth planet (Planet X) causes catastrophic comet showers on Earth at intervals of approximately 27 million years. 

In the beginning of this year, researchers at Caltech (led by Professor Mike Brown) proposed the existence of Planet X on the outskirts of our solar system. They based their planetary detective work on orbital anomalies of objects within the Kuiper Belt, a disc-shaped region past Neptune that’s home to comets and larger space bodies. The researchers surmised that such a planet would be 10 times the mass of Earth.

If you’re wondering, Planet X is so named because at the time it was originally theorized, Pluto was still considered the ninth planet. Dr. Daniel Whitmire and his colleague, John Maltese, first proposed a connection between comets caused by Planet X’s orbit and mass extinctions on Earth all the way back in 1985. But with the Caltech research coming into focus, their theory got new life.  

They believe that as Planet X’s tilted orbit around the sun slowly rotates, and as it passes through the Kuiper belt every 27 million years or so, it knocks comets into the inner solar system. These comets smash into Earth, causing all manner of cataclysmic destruction, and also disintegrate in the inner solar system nearer the sun, reducing the sunlight that’s reaching Earth.

Research based on the paleontological record shows evidence of regular comet showers dating back 500 million years.

Daniel Whitmire’s paper is published in the Monthly Notices of the Royal Astronomical Society.


Photo: Artist's impression of a 1000km-diameter planetoid hitting a young Earth. Credit: Don Davis / NASA.