Thousands of years ago the sky gazers of
the classical world knew about six planets:
Mercury, Venus, Earth, Mars, Jupiter, 
and Saturn.
Thanks to the invention of the telescope,
 Uranus was discovered in 1781.
But discrepancies in its orbit meant
that something was tugging at it.
Sure enough that something turned out
to be Neptune.
Ever since scientists have wondered if there might be yet another planet in our solar system
sometimes called Planet X.
Now astronomers have strong evidence for one.
A planet roughly the size of Neptune
with a mass ten times the
Earth's and a thick atmosphere of
hydrogen and helium.
Just as Neptune was predicted based on its influence on Uranus,
the evidence for Planet X is
indirect. Astronomers observed six small
solar system objects and noticed they
come closest to the Sun in a unique
configuration. There's only a one in
fifteen thousand chance that this
orbital clustering is a coincidence. It
is much more likely that Planet X has
shepherded the six objects into their
orbits.  This explodes our conception of
the solar system because Planet X would
loop around the Sun unimaginably far
away, in a strange elliptical orbit so
far away that it takes fifteen thousand
years to make the trip.  By comparison
Neptune's orbital period is 165 years.
Of course, not everyone will be convinced of Planet X until we have visual proof.
Researchers are now using one of the
world's largest telescopes, Subaru in
Hawaii and they say they have a
reasonable chance of finding Planet X in
the next five years
Once spotted, we can welcome Planet X
as the ninth planet in our solar system.
