Planet 9
Too far out to be easily spotted by telescopes, the potential unseen
planet appears to be making its presence felt by disturbing the orbits
of so-called Kuiper belt objects, said Rodney Gomes, an astronomer at
the National Observatory of Brazil in Rio de Janeiro.
Kuiper belt objects are small icy bodies—including some dwarf planets—that lie beyond the orbit of Neptune.
Once considered the ninth planet in our system, the dwarf planet
Pluto, for example,(Never Fear Pluto, I still believe you're a planet, mighty at heart!), is one of the largest Kuiper belt objects, at about
1,400 miles (2,300 kilometers) wide. Dozens of the other objects are
hundreds of miles across, and more are being discovered every year.
What's intriguing, Gomes said, is that, according to his new
calculations, about a half dozen Kuiper belt objects—including the
remote body known as Sedna—are in strange orbits compared to where they
should be, based on existing solar system models. (Related: "Pluto Neighbor Gets Downsized.")
The objects' unexpected orbits have a few possible explanations, said
Gomes, who presented his findings Tuesday at a meeting of the American Astronomical Society in Timberline Lodge, Oregon.
"But I think the easiest one is a planetary-mass solar companion"—a
planet that orbits very far out from the sun but that's massive enough
to be having gravitational effects on Kuiper belt objects.
Mystery Planet a Captured Rogue?
For the new work, Gomes analyzed the orbits of 92 Kuiper belt
objects, then compared his results to computer models of how the bodies
should be distributed, with and without an additional planet.
If there's no distant world, Gomes concludes, the models don't
produce the highly elongated orbits we see for six of the objects.
How big exactly the planetary body might be isn't clear, but there are a lot of possibilities, Gomes added.
Based on his calculations, Gomes thinks a Neptune-size world, about
four times bigger than Earth, orbiting 140 billion miles (225 billion
kilometers) away from the sun—about 1,500 times farther than Earth—would
do the trick.
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