Comet Lulin

The unusual celestial body, which is about 300,000 miles wide and some 38 million miles away, was due to appear just after midnight, close to Saturn during its first visit to the Earth's inner solar system.

The comet has a green hue because of the chemicals in its head, or coma, however, viewing it could be challenging for novice astronomers.

Discovered only a year ago, the comet gets its green colour from a poisonous, cyanide-like gas in its atmosphere.

The Swift satellite has recorded simultaneous ultraviolet and X-ray images of the comet.

A comet is a clump of frozen gases mixed with dust. These "dirty snowballs" cast off gas and dust whenever they venture near the sun.

Formally known as C/2007 N3, Comet Lulin was discovered last year by astronomers at Taiwan's Lulin Observatory.