kuiper_belt.html

Kuiper Belt

Roughly 10 billion icy objects outside the orbit of Neptune.

Although believed to exist since 1930's, only discovered in 1992 because objects are far away and thus faint.

Most of the bright KBOs are the same as a 100 watt light bulb on the Moon.
Exception is Pluto because it is covered by bright frost and so reflects 90% of sunlight.
Objects like the Moon reflect only a few percent.
That is why scientists originally believed that Pluto was much bigger than it is.