Scientists at NASA have discovered a nearly invisible ring around Saturn. Spotted by Spitzer Space Telescope, the ring is so large that it would take one billion Earths to fill it. The ring's orbit is tilted 27 degrees from the planet's main ring plane. The bulk of it starts about 6 million kilometres away from the planet and extends outward another 12 million kilometres. Its diameter is equivalent to 300 Saturns lined up side to side. NASA Jet Propulsion Laboratory said its entire volume can hold one billion Earths. A paper about the discovery authored by Anne Verbiscer, an astronomer at the University of Virginia and two others was published today in the journal Nature.<br/>