Goodbye Moon! But Will The Green Comet Still Show?

Notice how fuzzy comet 45P/Honda-Mrkos-Pajdusakova is. No tail either. It faded and lost its tail soon after after passing closest to the sun on December 31. This photo was made on Feb. 8, the last dark, moonless morning. Credit: Chris Schur

Last week, several people asked about seeing “the comet.” They meant 45P/Honda-Mrkos-Pajdusakova — a mouthful, so the comet made sense. I’d written about 45P in an earlier blog when it was visible in the morning sky just before dawn and after moonset. But last Thursday, moonlight encroached on this fuzzy, spread-out object and pretty much blanked it from view.

Because 45P passed just 7.7 million miles from the Earth on Saturday — close as comets go — there was some hyperventilating in the press about spotting the object, which glowed a pretty emerald green in time exposure photographs. Only problem: the full moon. While it gaveth the pretty penumbral eclipse, it tookith the comet away.

This map shows the comet’s nightly location around 10 p.m. CST now through Feb. 19. It passed nearest Earth on Feb. 11 and is now headed back out to deep space beyond the asteroid belt. Still relatively near our planet, 45P moves quickly from Bootes across Canes Venatici (Hunting Dogs) and into Coma Berenices in the coming nights. Stars are shown to magnitude +8. Click for a large version. Map: Bob King, Source: Stellarium

But starting tonight, the waning gibbous moon rises late enough to let the comet shine in a dark sky. You’ll find it very low in the northeastern sky in the constellation Bootes the Herdsman not far from the brilliant orange star Arcturus. The comet will be about 10° high (one fist) around 9:30-45 p.m. local time 15 to 30 minutes before moonrise tonight depending on your latitude. Northern states and Canada are favored.

The comet continues to climb away from the eastern horizon at the same time the moon rises later and later. By tomorrow night, we’ll have more than an hour of dark sky, so it will be even easier to track down this interplanetary fuzzball.

This black and white map might be easier for you to use while outside with binoculars or telescope. It shows the comet’s nightly location into early March. Stars are shown to magnitude +8 and north is up. Click for a large version and then make a print out. Created with Chris Marriott’s SkyMap software

Since no one’s reported observations in the past few nights, it’s hard to say how bright 45P will be. Last week, it looked like a puff of smoke glowing at magnitude +8. From a dark sky, I saw it easily in my 10×50 binoculars as a hazy patch of light nearly the size of the full moon. It was pretty spread out, and I had to know just where to look. By now, the comet should maybe a magnitude fainter and difficult (impossible?) in ordinary binoculars but still visible in large binoculars or a 4.5-inch or larger telescope.

Use these maps to help guide you to 45P. This week and next will be the last times to see it before its next bright return in October 2032. I’ll be watching for it the next clear sky and will report back. Be sure to stop by later for an update. One last bit of news — as of today, there are 3,450 known comets.

** UPDATE: Great news! 45P is still hanging in there. I saw it Wednesday night (Feb. 14) in 10×50 binoculars 15 minutes before moonrise. The comet remains very diffuse and quite large — about ½° across or the size of a full moon — but faint and very spread out. I estimated its magnitude at +8.3. 45P  should become a bit easier to see as it climbs higher into a dark sky in the next couple nights.

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