Scientists believe they have discovered the Solar
System's 10th planet.
It was found by astronomers using a telescope near
San Diego in California, America.
The planet has yet to be given a real name by the
International Astronomical Union - but at the moment it is called
It was discovered back in January this year but
was found on a photograph taken of the sky in October 2003. There
have been so many pictures taken for this search that it's taken
over a year for the scientists to get round to checking the pictures.
The new planet (circled)
Over the last couple of years there have been discoveries
of two other objects, Quaoar and Sedna. Both of them are smaller
than Pluto and are thought to be asteroids rather than planets.
560 years for one orbit
The Earth takes one year to go around the Sun.
This new planet is so far away from the Sun
- about 97 times further than the Earth - that it takes 560 years
for it to complete one orbit.
At that distance, if you were to hold a pin at
arms length, then the head of the pin would cover the Sun. It's
also pretty cold out there too - as there wouldn't be much heat
from the Sun, the surface temperature is only likely to be around
-243 degrees. Pretty chilly!
Half the size of the Moon
By looking at the light we receive from this new
planet, we can also work out how big it is. It turns out that it’s
bigger than Pluto, at about 1,200 km across. That still only makes
it about half the size of the Moon though.
Anyone wishing to see the new planet will be disappointed.
Whilst it is in the skies over Norfolk, large telescopes will be
needed to see it and even then it will only appear as a faint spot