Brightening a millionfold since its discovery in June 2011, the icy interloper has already become easily visible by the naked eye from the Southern Hemisphere as a distinct tail of gas and dust. (Related: "New Comet Found; May Be Visible From Earth in 2013.")

Astronomers originally stumbled upon the comet nearly two years ago while searching for potentially hazardous asteroids. Using one of the world's largest digital cameras, on Hawaii's Pan-STARRS telescope—the comet's namesake—the team snagged a faint image of the comet while it was still more than 700 million miles (1.1 billion kilometers) away, between the orbits of Jupiter and Saturn.

What gave it away was its fuzzy appearance, which is caused by the melting ice and released gases