[Sopater]

direct or even indirect observations of this body are impossible

If it is impossible to either directly or indirectly detect this body, why is it even "hypothetically" believed to exist?

[silverleaf]

http://www.space.com/scienceastronomy/astronomy/outer_planets_991014.html

[SunkenCiv]

...and

http://www.newscientist.com/article/mg20126932.200-is-there-a-planet-x.html

Probably I’ve posted something on John Matese (Google John Matese site:freerepublic.com).

[helpfulresearcher]

Every object in our solar system has gravity that pulls on every other body. When an object travels through space one can tell by the wobbles in its path when some heavy body is pulling on it from some direction. One can use this information to calculate the mass and location of the unseen heavy body.

This is how planet X was “discovered”. Its location is so far from the sun that it must be cold, and other bodies out that far have been icy objects. (Volatile materials boil off from the inner planets and then get cold trapped by planets out far from the sun where it is colder. (Kind of like your warm breath freezing out on your window in winter.)

It is hard to see this body because it is cold, dark and far away. As to the size of it, they have to guess what it is made of and then use the guessed density to calculate the size. Its not impossible to detect, just too hard for us at the moment.

The last bit in the article about planets falling into the sun or each other is hooey. We might have asteroids hit a planet, or something come from outside our solar system to mess things up, but that is way beyond unlikely. The vast majority of objects with erratic paths crashed into planets and each other long ago so the only ones left now have pretty regular orbits that do not intersect.

[helpfulresearcher]

They thought they saw it in 2005: http://science.nasa.gov/headlines/y2005/29jul_planetx.htm as a freeper posted above . I was wondering if Hubble had been used to look for it yet, and could not find any reliable images. If it had been found then it is likely Hubble would have been used to image it.

Apparently the jury is still out on the whole planet x thing. At http://space.y2u.co.uk/Astronomy_Planet_X.htm there is a good discussion of Planet X. Previous observations were found to be unreliable, and gravitational data was noisy, but more recent data suggests something may be there but not easy to locate precisely.