Planet X? No, that idea can be crossed off the list then

18 March 2014

For a long time astronomers believed, or hoped, there was a Jupiter, or Saturn, size planet lurking out in the distant reaches of the solar system. The presence of such a body, commonly referred to as “Planet X”, they thought, might account for the odd orbital paths of some of the other outer planets, dwarf planets, and various other Trans-Neptunian Objects (TNO).

But no, a NASA backed mission, that has spent just over a year scanning the sky, did not find any evidence of a such planet:

This news comes from a paper analyzing observations by WISE, the Wide-field Infrared Survey Explorer, a scrappy little mission that spent 13 months mapping the entire sky in infrared wavelengths. This is where warm objects are bright, things like dinky stars, asteroids, galactic dust, and more. WISE was very sensitive and was able to see objects that were pretty faint. For example, it found tens of thousands of previously undiscovered asteroids, some of which get pretty near the Earth. These glow in the infrared, heated by the Sun. What it didn’t discover, though, was another giant planet in our solar system. And it’s pretty definitive: It would’ve seen a planet the size of Saturn out to a distance of 1.5 trillion kilometers, more than a tenth of a light year! A planet the size of Jupiter would’ve been seen out to twice that far.

I imagine it’s possible there are other, much smaller planets, or dwarf planets, yet to be detected, out in the solar system’s far reaches though.

Originally published Tuesday 18 March 2014, with subsequent revisions, updates to lapsed URLs, etc.