The year 2013 is certainly living up to its expectations as being the "Year of the Comets". With both Comet PANSTARRS and Comet ISON warming up on the sidelines, Comet Lemmon (C/2012) is already making Southern Hemisphere news as the star of the show.
While looking for Near-Earth objects, Alex Gibbs discovered Comet Lemmon (C/2012) on March 23, 2012 while participating in the Catalina Sky Survey (CSS). Back then, the five mile wide blip on the astronomical radar screen was glowing at a feeble magnitude 20, but it didn't take long before the comet began to change. At the moment, this traveling space rock is doing some pretty spectacular things - including being far brighter than anticipated. Currently near unaided eye visibility, the comet is expected to continue to intensify as it nears the Sun, possibly glowing as brightly as magnitude 5 at perihelion.
What makes Comet Lemmon (C/2012) so special? Presently it is being incredibly photogenic, sporting a long dust tail, an ion tail and brilliant color. Thanks to its chemical composition of a colorless, toxic gas called cyanogen and a companion volatile known as diatomic carbon, this icy visitor from the Oort Cloud appears green when exposed to sunlight. This makes Comet Lemmon quite beautiful in appearance and also makes for a wonderful opportunity for study. Astronomers are able to examine these pristine materials spectroscopically as the comet sublimates - a chance to study the impact of the solar winds and take a look at materials which share their origin with both stellar atmospheres and the interstellar medium.
As it approaches the Sun, Comet Lemmon will become even more visible - but where is it now? Easily seen in both binoculars and small telescopes, it is currently only accessible to Southern Hemisphere observers and about to reach the zero hour on the ecliptic plane on February 24th. It will be moving rapidly across the sky each night and soon be readily apparent to the unaided eye as it crosses into the constellation of Phoenix by March 7th. It will continue to head north and move into the constellation of Sculptor by March 17th. Don't delay your observations, because Comet Lemmon makes its closest approach to the Sun - perihelion - on March 24th. At this time it will be roughly the same distance from Sol (the Sun) as the planet Venus, but it will be hidden from our point of view by the Sun's glare.
As April opens, it is time for Northern Hemisphere viewers to begin planning for observations of Comet Lemmon. By mid-month it should become visible at lower latitudes as it enters into the constellation of Pisces. Since it will be placed just a few scant degrees ahead of the dawn glow, make sure to choose an observation point where you have an unobstructed eastern horizon and reasonably dark skies with good seeing. On April 19th, Comet Lemmon will cross the celestial equator and be ready to dazzle the sunrise skies. Comet Lemmon (C/2012) will remain in the direction of the constellation of Pisces as it exits our solar system - staying visible to most amateur telescopes for a short period of time. By the beginning of May, it will have dimmed to the extent that it will be very difficult to pick out of brightening skies, even with the help of a telescope.
As always, there are no guarantees that Comet Lemmon will continue to perform. As amateur astronomers well know, even the most celebrated of comets can be an incredible sight one night, only to break up and fizzle away when we least expect it. Even though it has been some 11,000 years, we do know this isn't Comet Lemmon's first trip through our neighborhood and there's always a chance it may disintegrate as it nears the Sun. However, never give up hope! Right now it is putting on an exciting show and there's no reason to believe it will stop. Just remember, there is only a small window of opportunity to view this comet, so plan accordingly. Choose your observing area in advance and have your equipment ready.
While getting up early in the morning isn't always an appealing prospect, having the chance to view one of the historic comets of 2013 is certainly worth the effort!