Astronomy Picture of the Day . ... Today is the first day of Autumn in the Northern Hemisphere of Planet Earth. ... Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae. ... Looking Down on Saturn . ... No Earth based picture could possibly view the night side of Saturn and the corresponding shadow cast across Saturn's rings. Since Earth is much closer to the Sun than Saturn, only the day side of the planet is visible from the Earth. ... February 2014 . ...