QUESTION:
Can the Hubble telescope can take pictures of the 10th missing planet
in our solar system?

ANSWER from Sanjay Limay on April 24, 1996:
If there were a tenth planet, HST should be able to take a picture of it. 
However, there is no evidence anymore that there is a tenth planet in 
our solar system.  The belief that there was a tenth planet was due to 
our previous inability to precisely model the motions of the outer planets. 
However, after the fly-bys of the outer planets (Jupiter to Neptune) by 
Voyager 2, we now know the masses of those planets better than we did 
before, and the new values are able to explain the motions of the outer 
planets to within the observational errors (especially for the older 
observations).  Thus, there is no reason to invoke a large planet beyond 
Pluto to tug the planets to perturb their orbital motions.

However, there are many small objects beyond the orbit of Pluto that have 
been discovered in recent years.  But these newly identified members of 
the solar system are too small be called planets or even minor planets as 
they are perhaps no more than about 50 km radius.