Saturn's spectacular system of rings is well known but it now turns out to be far bigger than ever imagined. The largest ring previously known lies at 3 to 8 times the radius of the planet. This is dwarfed by the new find, which stretches from 128 to 207 times the radius of Saturn, and is 40 times as thick.
The ring's low density kept it from being discovered until Anne Verbiscer of the University of Virginia and colleagues used data from the Spitzer space telescope's multiband imaging photometer to make out the ring by its thermal emissions in response to being heated by sunlight. A bonus from this discovery is understanding why Iapetus – one of Saturn's moons – is mysteriously dark on one side. It seems this darkening is from material falling from the newly discovered ring.
Further reading
A J Verbiscer et al. 2009 Nature, advance online publication, doi:10.1038/nature08515.