What do you call an outer Solar System object that is larger than Pluto?
Nobody is yet sure.
The question arose recently when
an object currently twice as far out as Pluto and not in the
plane with the rest of the planets, was
to be 30 percent wider than
UB313's size was measured by a noting its distance from the
Sun and how much
infrared light it emits.
Previous size estimates were based only on visible light and greatly
affected by how reflective the object is.
Whether 2003 UB313
is officially declared a planet will be answered shortly by the
International Astronomical Union.
In the above picture, a scientific artist has imagined
UB313 in its
distant orbit around the Sun coupled with a hypothetical moon.