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.


The discovery sequence for Comet PanSTARRS (C/2011 L4), showing the 19th-magnitude object's motion against background stars from 9:20 to 10:23 Universal Time on June 6, 2011.

PS1 Science Consortium

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.


Image of Joe Stieber

Joe Stieber

June 16, 2011 at 1:15 pm

Why use non-standard names for comets? They should be called C/2010 X1 (Elenin) and C/2011 L4 (PANSTARRS).

Is the second paragraph, you refer to comets NEAT and LINEAR. There are dozens of comets with those names as a suffix, so which ones do you actually mean?

I could make similar comments about Comets McNaught and Hale-Bopp (presumably C/2006 P1 and P/1995 O1 respectively), but I don't want to belabor the point.

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Image of Jakub Černý

Jakub Černý

June 16, 2011 at 3:09 pm

If this comet is most likely dynamically new comet from oort cloud. That means that will probably brighten slower then expectation in article. Probably this comet will be only near 4 mag close to horizon after perihellion. But we can be maybe surprised.

And one more note, from Hale-Bopp we could very good observe comet Ikeya-Zhang in 2002 which had magnitude 3 and was nice naked eye objekt with few degree naked eye tail.

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June 24, 2011 at 5:50 pm

We won't see it. The world ends in December 2012....

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June 25, 2011 at 4:35 pm

Actually I think the whole idea of comets being named after automated instruments is ridiculous. It results in a lot of confusion ie there are nearly 200 comets named LINEAR!

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George Eberts

August 29, 2011 at 10:47 am

I just returned from the Black Forest Star Party and we were watching a fairly bright comet pass near M71 in Sagitta. Where on the S & T website did you report this? Where's the finder chart? I searched as soon as I got back and there's nothing I can find!

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