Planet Tyche?

A couple of astronomers think that they have evidence for a new planet, which they have named Tyche. If Tyche exists (as the Bad Astronomer points out, evidence is not proof)

If Tyche exists, it is so far away, 2,500 AU (1 AU = distance from the Sun to the Earth), that it has no measurable effect on the orbits of the planets we now know (the traditional mechanism for discovering new planets). At that distance, it would take 124,242 years to orbit the Sun (assuming a circular obit). This article says that Tyche would be 15,000 AU out, which would result in a Tychean year being roughly half-a-million of our years. Voyager 1 is a skosh over 116 AU from the Sun, Voyager 2 is 95 AU away; so unless some new technology is developed for really fast space travel (along with a way to deflect stuff from collisions), we're not going to get a probe near this planet anytime soon, even if it does prove out.

One of the definitions of a planet by the International Astronomical Union is that a planet "clears its own orbit" of other stuff. I don't know how they could begin to tell that for an object so far away.

Look at it this way: In space, light travels about 186,000 miles a second. The Moon is just under two light-seconds away, which was far enough to occasionally mess up a conversation between the Apollo spacecrafts and Mission Control. Tyche would be just over two light-weeks away at the nearer estimated distance or just under three light-months at the further distance.

If Tyche is really there, it would be as unreachable to us as the Moon was to humans in the 15th Century. It'll be interesting to see if the planet appears in Roberta X's story.