Oh right. Well that's not such a difficult program to write; you just need to know how to draw a sphere, maybe with a bitmap representation of the surface, then draw 10 spheres (sun+9 planets), to whatever scale is appropriate, and move the planets around the sun at comparatively realistic rates.
Do the orbits need to be circular or elliptical?
Do you need to include moons? Asteroids?
How much time should the longest revolution of a planet around the sun take?
Is it OK for the planets to be spherical or do they have to be more realistic than that?

mugnebot: could you clarify the comment "I need too. I have no time"? Is this a programming assignment of some kind (college etc)? Why do you have no time? Are you on an programming course that includes OpenGL? If you want us to help you out here then you need to be honest with us about your situation.

Also how much code have you written so far and where are you stuck?