Re: why doesnt the sun have rings?

Depending on your point of view, our sun does have a ring... or a couple of 
 belts and even a cloud!   Because of Jupiter's tremendous tidal forces, no 
planet formed in the interval between it and Mars. The asteroids form an 
orbiting ring around our star, although that area is traditionally referred 
to as the Asteroid Belt. 
     Further out, much further out, the Kuiper Belt of comet nuclei would 
look like a vast, tenuous ring to a distant alien astronomer. That same 
obwerver might notice the huge Ort Cloud of cometary nuclei which surrounds 
our solar system on all sides. Occasionally one of the Kuiper or Ort 
objects is perturbed and falls through the solar system and we Earthlings 
observe a comet. Once a great while, one of these comets smashes into a 
planet, as Shoemaker-Levy did to Jupiter in 1996.
     Other stars have been observed to have great rings of dust and gas. 
Check out the NASA web sites for Hubble photos of Beta Pictoris. We think 
some of the rings around stars may someday form planets and solar systems 
like ours; according to that theory of planet formation, WE were the rings 
around our sun long, long ago!
      Thank you for an exciting question. Keep your eyes on the stars.
Jim Foerch
James C. Veen Observatory
Lowell, Michigan