Stars Beyond Saturn

Hi Ana-Marie,

I'm not sure, but I think you're referring to the ancient Greek view of the solar system. In this system, the Earth was the center of the universe. The planets (of which six were known, out to Saturn), and the Sun revolved around the Earth. Beyond this, the stars were fixed in space. This seems like a reasonable conclusion to draw, for a couple reasons. The Greeks noticed the planets were moving, but the stars were not, so it made sense that the planets were revolving around the Earth while the stars were fixed. This is shown in the figure below.


Photo from Minnesota State University,

However, this view of the solar system is very outdated. The stars (besides the Sun) are much farther away from the Earth than the other planets are, and the whole system makes up the Milky Way galaxy! These other stars, like our Sun, rotate around the center of the Milky Way at a range of distances from the center. This movement can be detected, and is being studied by satellites like and (which will be launched in 2013).

Thanks for the question!
Ben M.

(published on 04/11/2011)