[bagels]

There are other ways besides seeing changes in orbits to confirm the existence of a body. Venus, Mars, Jupiter, and Saturn are easily seen with the eye, for instance.

Planet 9 might be confirmed with infrared surveys as a post from last week discussed or some other method.

[adrian_b]

You are right, I was only replying to the parent article, where the incorrect argument was stated, that the orbits pointing to an external attractor mean that it exists now in that direction.

There may be one or more big planets at great distances from the Sun, but not for the reason stated in the parent article, which is better explained by an ancient star flyby.