Back...
The Tenth Planet
August 2005
Discovery Image
Motion through the Stars
Size
The Kuiper Belt
Sources:
NASA
Sky & Telescope
|
The discoverers attempted to image the new planet with the Spitzer Space Telescope
but didn't detect it. That placed an upper limit on the size: 3,000 kilometers across.
Its lower limit is derived from its brightness. Even if its surface is 100 percent
reflective, it would still be larger than Pluto, which is 2,250 km across.
|