Life on Earth has little to fear from the hypothesized Planet Nine, astronomers say.
Some scientists have suggested that a big undiscovered body lying on the far outer reaches of the solar system could be responsible for many of the mass extinction events throughout Earth’s history, by shaking up the distant comet repository known as the Oort cloud and sending some its denizens screaming toward our planet.
But Planet Nine — a newly proposed but not yet confirmed world perhaps 10 times more massive than Earth that’s thought to orbit far beyond Pluto — probably could not have triggered such “death from the skies” events, researchers said.
“I suspect it has something like zero effect on us,” said Mike Brown of the California Institute of Technology (Caltech) in Pasadena.
Brown and lead author Konstantin Batygin, also of Caltech, suggested the existence of Planet Nine in a paper that was published last week. They infer the planet’s presence based on indirect evidence: Computer models suggest that a distant, unseen world has shaped the strange orbits of a number of small objects in the Kuiper Belt, the ring of icy bodies beyond Neptune.
Researchers say an anomaly in the orbits of distant Kuiper Belt objects points to the existence of an unknown planet orbiting the sun.
Researchers say an anomaly in the orbits of distant Kuiper Belt objects points to the existence of an unknown planet orbiting the sun. Here’s what we know of this potential “Planet Nine.”
Credit: by Karl Tate, Infographics artist
Planet Nine likely has an elliptical orbit, coming within 200 to 300 astronomical units (AU) of the sun at its closest approach and getting as far away as 600 to 1,200 AU, Brown said. (One AU is the distance from Earth to the sun — about 93 million miles, or 150 million kilometers).
Neptune orbits about 30 AU from the sun, and Pluto never gets farther than 49 AU from our star. So Planet Nine, if it exists, is very distant indeed — but not distant enough, Brown said, to stir up any of the trillions of comets in the Oort cloud, which begins perhaps 5,000 AU from the sun.