Jupiter-sized Planet Lurking in Oort Cloud?

[sanman]

Lately I've read some articles about the possibility of a Jupiter-sized planet hidden in the Oort cloud.

This assertion is based on analysis of cometary deflections and observations of Sedna.

What is the likelihood of this?

We all know that there must be lots of planet-sized stuff out there besides Sedna, but Jupiter-sized?
If Neptune and Uranus have been known for so long, then how could a Jupiter-sized planet remain undetected for all this time?

 

[D H]

The consensus among most solar system astronomers is "No". They have pretty much nailed the dynamics of the solar system pretty using just the known bodies in the solar system. The last nail in the Planet X coffin was an adjustment to Neptune's mass based on the very well-observed flyby of Voyager. Before this adjustment, there was a small unexplained discrepancy in Uranus' orbit.

Every branch of science has its share of not-quite woo-woos, astronomy included. The news media likes the woo-woos more than the boring non-woo-woos. The non-woo-woos are boring.

The best current answer of Sedna's currently unexplained eccentricity is that we don't know. Most astronomers say just that. A well-reasoned "we don't know" does not sit well with journalists. They want a sensationalistic answer to help garner readers. More readers = more $$ from advertisers. Anything beyond "we don't know" is baseless conjecture. Some fringish astronomers like to make baseless conjectures, partly because the newsies eat that stuff up.