Saturn's iconic rings will temporarily disappear this weekend in a rare celestial event that hasn't happened since 2009.According to Space.com, the planet's rings align perfectly with Earth's line of sight every 13 to 15 years, making them appear nearly invisible. It's called the "ring plane crossing." The phenomenon will start on Sunday and extend for a few days. Saturn's rings will appear as a very thin line in the middle of the planet for a few months afterward. RELATED STORY | Astronauts won't get overtime for their extended stay aboard the Space Station, NASA saysUnfortunately, most people won't be able to see Saturn-sans-rings because the planet will be on the eastern horizon in the morning twilight sky. NASA predicts the phenomenon will return in 2038 and 2039. ...read more read less