Is 'Planet 9' a Kidnapped Ex-Exoplanet?
The mysterious origin of the hypothetical planet that may be lurking in the outermost regions of the solar system just got weirder.
Astronomers are working hard to track down any visible signs of a large undiscovered planet pottering around in a distant corner of the solar system. We have a pretty good idea that it exists -- its gravity seems to be tugging on a few Kuiper belt objects (KBOs) -- but there has yet to be any direct visual clue that it's really out there.
The fact that it hasn't been picked up by infrared or optical surveys is actually a fairly good indicator as to how far away and how big this thing is; by ruling out where we know it isn't, we can put limits on the planet's physical size and take a stab at its composition. Granted, this isn't the first time astronomers have found clues to a massive object lurking in the outer solar system, but this time the evidence is pretty compelling.
NEWS: 9th Planet May Lurk in the Outer Solar System
Astronomers have already done some work in guessing what Planet 9 might be made of, but on Tuesday (May 31) researchers threw a wildcard into the mix: What if Planet 9 isn't from 'round these parts? Could it be an alien world, kidnapped by our sun from its home star billions of years ago? In other words, is Planet 9 an ex-exoplanet?
"It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard," said astronomer Alexander Mustill, of Lund University, Sweden, in a statement.