On Friday 12 May astronomers will see 73P/Schwassmann-Wachmann 3 become the closest comet to pass Earth in 23 years. The comet is much smaller than the naked-eye comets Hyakutake (1996) and Hale-Bopp (1997) � but well worth looking at through binoculars. This comet, unlike any others to have passed the Earth recently, is in the process of breaking up.

73P/Schwassmann-Wachmann 3 is currently in the constellation Cygnus, the Swan, which makes up part of the Summer Triangle. From a dark location observers will be able to spot the larger fragments with good binoculars, from midnight.

73P/Schwassmann-Wachmann 3 will pass within 5.5 million miles of Earth � just 20 times further than the Moon. Whilst this distance is small in astronomical terms, the comet is not close enough to pose any threat to the Earth. However, scientists predict that the debris left behind by the comet may result in a small meteor shower in a few years.

Scientists have been watching 73P/Schwassmann-Wachmann 3 with larger telescopes for several weeks, and hope their observations will tell us more about the composition of comets. The image above shows fragment B of the comet and was taken by staff at the National Space Centre in Leicester, using the Faulkes Telescope North. Click here for a larger image.

Don Yeomans manages NASA's Near Earth Objects Program office at the Jet Propulsion Laboratory in California, USA. It is his job to keep track of the fragments and tell astronomers where to find them. "It's driving us nuts; fragments of fragments of fragments. It�s doing its best to make our lives miserable," he said, laughing.

As the comet passed Jupiter, the gas giant�s gravity began tearing it apart. The comet has now broken into 59 fragments and will continue to disintegrate as it makes its close encounter with Earth.

The comet was discovered in 1930 by the German astronomers Arnold Schwassmann and Arno Arthur Wachmann. Calculations revealed that it orbits the Sun once every 5.5 years, but it wasn't seen again until 1979. Astronomers missed it in 1985, but found it again in 1990. When it returned in 1995 astronomers realised it got dramatically brighter in a short period of time, and then they realised it had more than one nucleus.