2) It comes from the edge of the solar system Pan-STARRS was flung into the inner solar system from the Oort cloud, a mass of icy bodies orbiting the sun from just beyond the orbit of Neptune out to a range 100,000 times the distance between the Earth and sun, NASA officials have said. A rogue comet's orbit is occasionally changed, bringing it closer to the sun than it has ever been before.
3) It is a "sungrazing" comet When a comet enters the inner solar system from the Oort cloud on a course that brings it extremely close to the sun, the object is known as a "sungrazer." On Sunday, Comet Pan-STARRS will be about 28 million miles (45 million km) from the sun.
Sungrazing comets have irregular orbits, making them unpredictable. Sometimes, their trajectories can even bring the comets close enough to collide with the sun. But if a sungrazer survives its close brush with the star, like Pan-STARRS has, the comet can brighten magnificently.
4) It almost faded away While astronomers initially thought that Comet Pan-STARRS could dazzle stargazers with its brightness, the comet exhibited some early signs that it wouldn't brighten as expected in the northern sky. Some astronomers predicted that the comet's magnitude - a measure of its brilliance - would fade, making it difficult to see once it passed above the equator, but now scientists expect that the comet may brighten even more when it passes close by the sun on Sunday, before fading quickly thereafter.