Recent sightings of great comets, or comets bright enough to be seen without the aid of special equipment, are Comet Lovejoy in 2011, Comet McNaught in 2007, Comet Hale-Bopp in 1997, Comet Hyakutake in 1996, Comet West in 1976, Comet Ikeya-Seki in 1965, Comet Skjellerup-Maristany in 1927 and Halley's Comet in 1910. Numerous comets too dim to be seen by anyone but astronomers regularly pass through the solar system.
The most recent great comet, Comet Lovejoy, discovered by Australian amateur astronomer Terry Lovejoy, was a member of a cluster of comets called the Kreutz comets that broke apart from a single large comet in the twelfth century. After Comet Lovejoy passed the Earth, it plunged through the Sun's corona and survived, exciting NASA and other scientists. This is remarkable because the comet's core is composed of ice.
Comet McNaught was distinguished by its long, spectacular tail visible for several nights in the southern hemisphere.
Comet Hale-Bopp, discovered by two amateur astronomers simultaneously in New Mexico and Arizona, caused a sensation when it passed close to the Earth in 1997. It was visible to the naked eye for a full year and a half and is considered the brightest comet seen for decades and one of the most observed comets of all time.