The Little Gem Nebula or NGC 6818 is a planetary nebula located in the constellation of Sagittarius. It has magnitude 10 and oval diameter of 15 to 22 arcseconds with a 15th magnitude central star. It was discovered by William Herschel in 1787. NGC 6818 is located in the constellation of Sagittarius (The Archer), roughly 6000 light-years away from Earth. The glow of the cloud is just over half a light-year across.