A rare green comet named Nishimura will be visible in the Northern Hemisphere until early next week. The comet, about a kilometer in size, will pass by Earth at a distance of 78 million miles on September 12. It will be visible near the Leo constellation, but binoculars are recommended to spot it. After its close encounter with the sun, the comet is expected to be visible in the Southern Hemisphere by the end of September. The comet was discovered by an amateur Japanese astronomer and is the third comet he has found.