After battling moonlight, Comet 45P/H-M-P returns for a final go-round in dark skies. Even better, it's up by 10 o'clock!
|Update (February 15, 2017): Arecibo Observatory has captured radar images of Comet 45P/Honda-Mrkos-Pajdusakova. It's only the seventh comet to be imaged using radar because comets rarely come close enough to Earth. Scroll down to see the radar image.|
It's rare for a comet to transition from pre-dawn object to evening target in only six days, but 45P/Honda-Mrkos-Pajdusakova's proximity to Earth made all the difference. When it passed only 7.7 million miles above our rooftops on February 11th, the green blob briefly sped across the sky at up to 9° a day.
Lucky for us, it's been traveling west towards evening, while the Moon's been moving east. That's why, starting tonight, 45P/H-M-P will once again be visible in a moonless sky. On the evening of February 14th, the comet will stand about 10° high in the northeastern sky just before moonrise. Depending on your latitude, you might get as little as 10 minutes up to a half hour of dark sky. Things quickly improve later in the week as 45P rapidly gains altitude as the Moon rises later and later.
45P/H-M-P got a lot of hype last week; unfortunately, the bright Moon put the kibosh on viewing such a diffuse object for small scope and binocular users. Not only that, but the comet wasn't as bright as expected. Some predicted a peak magnitude of around +6.5, but it never got brighter than +8. Such is the nature of these cosmic fuzzballs. They can thwart our expectations, follow due course, or put on a surprise show.
As we move into a moonless observing window, the comet remains spread out and tailless. Because it's well past perihelion and leaving Earth in the dust, it's expected to fade this week to around magnitude +9. That makes it fringey for 50-mm binoculars but likely still visible from a dark sky.
Telescope-toting observers will do better and enjoy views of what resembles a puff of smoke or mist, with a somewhat more "condensed" or compact central region. 45P/H-M-P still has legs! Pushing ever westward from Boötes through Canes Venatici and into Leo, on February 14th, the comet covers 6° in 24 hours, 5° on February 15–16, and 4° on Feb. 16–17. When you do find it in your telescope, take a peek a little while later, and you'll notice movement to the west at the rate of about 12′ an hour.
The best time to view the comet in the coming week will be from around 10–11 p.m. local time, when it's well placed in the eastern sky. 45P/H-M-P should fade rapidly by late February, so be sure to see it while you can. At its next bright return in October 2032, the comet's expected to reach magnitude +7. I'll keep an eye on it, so check back here for an update in a day or two. Happy hunting!
** UPDATE: Great news! I was able to spot the comet in 10x50 binoculars 15 minutes before moonrise tonight (Feb. 14). It appeared quite large — about 30′ or a full moon diameter wide — but of course faint and very diffuse with an estimated magnitude of +8.3. In just a night or two, the comet will be considerably higher before moonrise and a little bit easier to see.
** UPDATE #2: The Arecibo radio dish spotted the comet too! Instead of visual observations, Arecibo captured radar images of the comet as it flew by Earth, making it the seventh comet to be imaged by radar. The image below shows 13 images collected over two hours of observation.