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According to Prof. Daniel P. Whitmire from the University of Arkansas, the suspected Planet Nine triggers comet showers linked to mass extinctions on Earth at intervals of about 27 million years.
Planet Nine is thought to be gaseous, similar to Uranus and Neptune; hypothetical lightning lights up the night side. Image credit: R. Hurt, IPAC / Caltech.

Planet Nine is thought to be gaseous, similar to Uranus and Neptune; hypothetical lightning lights up the night side. Image credit: R. Hurt, IPAC / Caltech.

Though astronomers have been looking for Planet Nine for over a century, the possibility that it’s real got a big boost recently when Dr. Konstantin Batygin and Prof. Mike Brown from the California Institute of Technology (Caltech) inferred its existence based on orbital anomalies seen in objects in the Kuiper Belt.

If the Caltech astronomers are correct, Planet Nine is a gas giant about 10 times more massive than Earth and could currently be up to 1,000 times more distant from the Sun.

Prof. Whitmire and his colleague, Dr. John Matese, first published research on the connection between Planet Nine (or as they called it ‘Planet X’) and mass extinctions in the January 3, 1985 issue of the journal Nature.

At the time there were three explanations proposed to explain the regular comet showers: an unknown planet, the existence of a sister star to the Sun, and vertical oscillations of the Sun as it orbits the galaxy.

The last two ideas have subsequently been ruled out as inconsistent with the paleontological record.

Only Planet Nine remained as a viable hypothesis, and it is now gaining renewed attention.

Prof. Whitemire and Dr. Matese’s hypothesis is that as Planet Nine orbits the Sun, its tilted orbit slowly rotates and the planet passes through the Kuiper Belt of comets every 27 million years, knocking comets into the inner Solar System.

The dislodged comets not only smash into the Earth, they also disintegrate in the inner Solar System as they get nearer to the Sun, reducing the amount of sunlight that reaches the Earth.

In 1985, a look at the paleontological record supported the idea of regular comet showers dating back 250 million years.

Newer research shows evidence of such events dating as far back as 500 million years.

Prof. Whitmire and Dr. Matese published their own estimate on the size and orbit of Planet Nine in their original study.

They believed it would be between one and five times the mass of Earth, and about 100 times more distant from the Sun, much smaller numbers than estimates of Dr. Batygin and Prof. Brown.

“What’s really exciting is the possibility that a distant planet may have had a significant influence on the evolution of life on Earth,” said Prof. Whitmire, who published his findings in the January issue of the Monthly Notices of the Royal Astronomical Society.

“I’ve been part of this story for 30 years. If there is ever a final answer I’d love to write a book about it.”