Merry Christmas and a happy holiday! I hope you're enjoying time with family and friends and a clear night is in the forecast. Should you poke your head out tonight, here's what's up.
At nightfall, a pretty crescent moon ornaments the dim constellation of Capricornus not far from Mars. Barely half a degree to the planet's east a 6-inch or larger telescope will net you Comet 15P/Finlay, now fading from its recent outburst. It's currently magnitude 9.6 with a little tail pointing to the east.
In a remarkable coincidence, comets have passed very close to the planet Mars twice this year. Comet Siding Spring drew physically close on and around October 19th, while Comet Finlay only appears next to the planet thanks to a lucky line-of-sight alignment.
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Later tonight, around 10 o'clock, look to the south. Orion has now climbed boldly into view along with sparkling Sirius and the "Winter Triangle" figure. Tucked below Lepus the Hare you'll find our Christmas comet, Lovejoy, now glowing at magnitude 5.5 and faintly visible to the naked eye from a dark sky location. Binoculars show it as a big ball of fuzz. For more information and a map showing its travels in the coming nights, click HERE .
Photos of Lovejoy show a huge coma or comet atmosphere more than half the size of the full moon tinted green from fluorescing carbon and cyanogen molecules; its super-skinny tail glows blue from light given off by carbon monoxide excited by ultraviolet light from the Sun.
If you now direct your gaze to the east around 10 p.m., Jupiter jumps right out. After Sirius and the moon, it's the brightest nighttime object the sky this winter. Use the planet to help you find the Sickle or head of Leo the Lion and its brightest star, Regulus.
Sharply-focused and steadily held 10x binoculars will show all four of its bright moons, assuming one or more aren't passing either behind or front of the planet or in eclipse. Lucky for us, Io, Europa and Ganymede will line up in a neat row east of Jupiter with Callisto well off to its west tonight. How many will you see?
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Finally, reports are coming in about a powerfully bright fireball that streaked across Japan's skies around 2 a.m. local time this Christmas morning. I've not been able to track down a brightness estimate, but the pictures show an object at least as brilliant as the full moon.
