From the perspective of PhysicsWeb: Kuiper Belt Objects 2003 UB313and 2003 EL61

Ref: http://physicsweb.org/articles/news/9/8/1/1

Astronomers may have discovered the tenth planet in our solar
system -- the first since Pluto 75 years ago. "2003 UB313", as
it is currently called, is about 97 times further away from
the Sun than the Earth -- more than twice as far away as Pluto.
However, it remains to be seen if the astronomical community
will accept 2003 UB313 as a fully fledged planet as many
astronomers argue that Pluto itself is not a proper planet.

See: http://physicsweb.org/articles/news/9/8/1/1