The (Northern) Winter Solstice happened yesterday, December 21, 2008 at 12:04 UT. Yeah, I’m sure you didn’t notice, but the days are getting longer from here on out. My longest night was spent with the best sleep I’ve had in a week. Now begins what I consider the best part of the night sky, the Winter constellations.
Right after sunset, Piscis Austrinus (PsA) is low on the SSW horizon. The reason I like PsA is Fomalhaut (alpha PsA). The magnitude 1.15, class A star has the distinction of being the first star where we tiny earthlings saw an extrasolar planet in the visible light spectrum, thanks to the Hubble telescope. Though not visible to the naked eye, Fomalhaut has a 25 AU debris disk circling at about 133 AU that emits a stunning amount of infrared radiation.
Right now, Venus is hanging around just west of Formalhaut. A month from now, on 21 Jan 2009, Venus will be in conjunction with Uranus. Watch for it.
Around 11pm local time, Orion, the naked-eye astronomer’s dream, is due south. The reddish Betelgeuse (alpha Ori) and blue Bellatrix (gamma Ori) mark the Hunter’s shoulders. bright blue Rigel (beta Ori) and the dimmer Saiph (kappa Ori) mark his feet. You can spend an entire evening lost in the wonders of Orion. Betelgeuse’s impressive 0.45 magnitude is more impressive when you know that it is 427 light years away. Not to be out done, Rigel’s 0.15 magnitude comes across 772 light years to brighten our winter sky.
Orion is one of the easiest constellations to find. Simply look for Orion’s belt, the three evenly spaced stars, Alnitak, Alnilam, and Mintaka, in a diagonal line. Look down and hanging from Orion’s belt is his sword. At first glance, Orion’s belt looks like three fuzzy stars, but if you look closely (you may need binoculars), some of the fuzziness will clear. The middle star, theta-1 Ori C, is blurred by the Great Nebula in Orion.
So what is Orion the hunter hunting? Where are his hunting dogs and what are they after? Where in the winter sky can we find one of our nearest star neighbors? Can we see any of our relatives up there? All this in our next installment of the winter sky unless you want to throw out your guesses in the comments.