March 7, 2013 | 8
This year is shaping up to be a great one for amateur sky-watchers. Toward the end of 2013, astronomers expect the recently discovered Comet ISON (officially designated C/2012 S1) to shine mightily as it approaches the sun—possibly glowing as bright as the full moon. (Comets are unpredictable beasts, though, and often fail to meet the most optimistic predictions for their visibility.)
Before the main event, though, Comet Pan-STARRS should provide a nice warm-up act. Pan-STARRS (aka C/2011 L4) is already visible in the southern hemisphere, and will ease into northern skies in the coming days.
March 12 or 13 will likely provide the first good viewing opportunity in northern latitudes, as Comet Pan-STARRS lingers over the western horizon at dusk [see illustration at right]. The comet will be viewable with the naked eye as it climbs higher in the sky throughout March, according to predictions issued by the Paris Observatory. But binoculars are always useful to help make out a comet’s tail or coma (the fuzzy cloud of dust and gas surrounding the nucleus), the visible features that distinguish comets from less-adorned asteroids.
A word about the odd-sounding names “ISON” and “Pan-STARRS”: Comets are usually named for the astronomer or the observatory that discovered them (Hale-Bopp for Alan Hale and Thomas Bopp, to use a famous example*). The new comets were found at the ISON (International Scientific Optical Network) Observatory in Kislovodsk, Russia, and at the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) telescope in Hawaii, respectively.
A double feature of prominent comets is relatively rare. Comets as bright as Pan-STARRS only come along once every several years or so on average, comet researcher Karl Battams of the Naval Research Laboratory explained in an email. “Of course it is an inherently random process, as it appears we might get at least two comets like that this year,” Battams added. “Or so we hope, anyway!”
* CLARIFICATION (3/8/2013): The original text of this post cited the example of Edmond Halley and Halley’s Comet as an instance where a comet had been named for its discoverer. But as a reader noted on Twitter, Halley’s Comet was not strictly discovered by Edmond Halley. The comet had been spotted previously—numerous times over hundreds of years, in fact—but Halley recognized its periodicity and predicted its return.