If you don't count Comet McNaught, which furtively grazed the horizon for a few days before its great southern-sky performance in 2007 and the unexpected brightening of Comet 17P/Holmes in late 2007, we northerners haven't had a truly satisfying comet-watching experience since Hale-Bopp in 1997. We're overdue!
Since then we've been teased and then disappointed a few times. Back in 2004 I looked forward eagerly to seeing two fuzzy iceballs by eye at the same time — a visual treat not achieved since 1911. But comets NEAT and LINEAR failed to live up to their advance billing. Comet Elenin (C/2010 X1), discovered last year, likewise might not perform as well as hoped when it peaks this coming September.So it's with some trepidation that I write about a promising discovery made two weeks ago. Comet PanSTARRS (C/2011 L4) was found by an automated survey telescope of the same name in Hawaii. For the record, that odd acronym stands for Panoramic Survey Telescope And Rapid Response System. It's a 1.8-m prototype for a quartet of military-funded scopes that astronomers hope to build on the lip of the extinct volcano Haleakala. Pan-STARRS 1 has had its share of development issues, but that's a story for another day.
Richard Wainscoat (University of Hawaii) reports that C/2011 L4 was first spotted on the morning of June 6th, then Marco Micheli, Lisa Wells and he followed up the next day with the 3.6-m Canada-France-Hawaii Telescope. As it turns out, observers at Mount Lemmon Observatory had unknowingly imaged it nearly two weeks earlier, on May 24th.
The comet is undeniably faint (19th magnitude) and distant (6.6 astronomical units or 610 million miles from us), with just a hint of a coma. But it didn't take dynamicists long to realize that this icy visitor is headed toward us. It will pass just 0.3 a.u. (30 million miles) from the Sun — though more than 80 million miles (130 million km) from Earth — in the first months of 2013.
I've used "first months" because for now the orbit remains uncertain — as of today celestial dynamicists at the Minor Planet Center predict a perihelion on February 5th, while their counterparts at NASA's Jet Propulsion Laboratory suggest it'll come a month later, and it might not occur until April.
Regardless, there's a possibility that Comet PanSTARRS could become a 1st-magnitude object around that time, sliding up from southern declinations to become an evening-sky adornment low in the west after sunset. At least that's how things look now — but let's not get too excited just yet. Check back here at a later date for updates.