On February 18th, 1930, American astronomer Clyde Tombaugh discovered the planet Pluto from a series of pictures taken the previous month at Lowell Observatory.

Related Websites
Send your students to these websites, or just take a look yourself:

See these images and marvel at the splendour of these planets.

http://pds.jpl.nasa.gov/planets/welcome.htm

The relative sizes of the planets and their moons.

http://www.nasm.si.edu/ceps/etp/ss/solsys_l.jpg

This site takes a look at Voyager and what it - and we - have learnt so far.

http://www.nasm.si.edu/ceps/etp/etp.htm

Lots more stuff on the planets

http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.html

Maybe you’d rather listen to them than look at them!

http://www.aquarianage.org/lore/holst.html