Misc: jan 99 " pretty fly for a white guy " was a no1 hit for who?

Questions

Our galaxy is commonly known as the ?

Which month has a diamond as a birthstone?

A heavenly body moving under the attraction of the Sun and consisting of a nucleus and a tail is a(n) ?

From 1979 until 2000 the most distant planet from the earth was ?

How many planets are there in our solar system?