Saturn's rings are already mind-blowingly large — about 70,000km across — but astronomers at the Leiden Observatory in the Netherlands have found a much more extensive ring system. At least they think they have — all they can actually see are shadows.
The discovery of the rings came about during observation of star j1407, a very young 'sun-like' star. While they were watching, they noticed that the star was undergoing a series of complicated eclipses, lasting for weeks. Upon further examination of the data, scientists hypothesised that this was caused by a series of rings surrounding j1407. They're exactly like those surrounding Saturn, but 'millions of kilometres' in diameter.
To put that in perspective, Matthew Kenworthy, the astronomer who created the most recent model, says that "if we could replace Saturn's rings with the rings around J1407b, they would be easily visible at night and be many times larger than the full moon."
Over time (we're talking astrological time, so millions of years), the rings will probably thin out and disappear altogether, as the matter that makes them up clumps together and forms satellites. But until then, you can stare at the hypothetical model above, and imagine what it would be like to have that hanging over your head. [Modelling giant extrasolar ring systems in eclipse via Rochester]