Natural N4

Peter Firus

Year 12 Swifts Creek Secondary College

Comet McNaught

Comets are small bodies composed of rock dust and ices. Most are thought to have originated from the Oort Cloud – debris left over from the condensation of the solar nebulae. They circle the Sun in highly elliptical orbits allowing them to come very close to the Sun. Some, like Comet McNaught, have nearly parabolic orbits which may take thousands of years to return to the Sun, or indeed never return.
Comet McNaught was first discovered on August 7, 2006 by Robert H. McNaught. It reached maximum brightness of an apparent magnitude of -6.0 in mid January 2007 as observed in the Northern Hemisphere. The comet was not quite as bright in the Southern Hemisphere where this image was taken (Swifts Creek, Victoria), reaching a maximum apparent magnitude of -4 to -5. This magnitude is comparative to the maximum brightness of Venus (-4.7). This brightness earned it the title “the Great Comet of 2007”. Although this image was taken a full week after McNaught was at its maximum brightness, it was still clearly visible to the naked eye.
The enormous curved tail of McNaught is caused by the force of the Sun's radiation pressure and solar wind acting on its atmosphere, or coma. The dust in the tail reflects the sunlight and is the chief reason that the comet is visible.