A reality check for comet PANSTARRS

Posted Jan. 20, 2013

Sometimes that shiny new phone or car doesn’t quite live up to expectations, but we often overlook their deficiencies and make our peace. We may have to do the same with Comet L4 PANSTARRS.

Observers in the southern hemisphere have watched the comet closely since it emerged from the solar glare last month. It’s presently loping along through Corona Australis, the Southern Crown, and visible shortly before dawn for those living down under. Not too many months ago, PANSTARRS was forecast to reach a brilliant magnitude 0 (equal to the star Vega) come early March this year. In recent weeks however, the comet has been lagging.

Amateur astronomers have noticed that its rise in brightness has been slowing down or plateauing of late. As of Jan. 19, 2013 the comet is a small, dense fuzzball of about magnitude 8 with a short tail pointing west. Binoculars show it as a dim glow.

With less than two months to go before the “big show”, this lag has made some ardent comet watchers revise their expectations of just how bright PANSTARRS will become.

Seiichi Yoshida, a Japanese amateur astronomer who maintains the excellent and most useful Weekly Information about Bright Comets site (http:// bit.ly/XSiHTV), originally pegged the comet at magnitude 0 in March but has now revised his lightcurve (graphical representation of a comet’s rise and fall in brightness) to show PANSTARRS topping out closer to magnitude 3 at best. His estimate is based upon past as well as the most recent observations.

If this holds true, what does it mean for comet watchers? A magnitude 3 comet is 15 times fainter than one shining at magnitude 0. While still visible with the naked eye, such a comet would not be a visual spectacle. Given that PANSTARRS will be brightest when relatively near the sun in evening twilight, it would appear faint without optical aid, but still be a striking sight in binoculars and telescopes.

Of course this could change again, so I wouldn’t get too worried yet. Comets are wonderful to follow in part because of their unpredictability. L4 PANSTARRS may yet have a few tricks up its sleeve. Stay tuned for more updates in the coming weeks.

King is the photo editor at the Duluth News Tribune

and an amateur astronomer who blogs at

astrobob.areavoices.com

Tags: life, science