Did you catch the conjunction of Jupiter and the moon last night? Amazing sight. For fun I tried to see how early I could spot Jupiter once the moon rose high enough to clear the trees.
In 8×40 binoculars the planet was a pale, grey-white dot against a blue sky at 4:08 p.m. 15 minutes before sunset. With the nearby moon making it easy to know exactly where Jupiter was, spotting it was a snap.
How about naked eye? That took a few more minutes. At 4:15 p.m. it flashed weakly in and out of view as a faint pinprick. I could barely hold onto it, yet 15 minutes later in the post-sunset sky, Jupiter was unmistakeable.
The best views came as twilight deepened into night and the pair combined their lights for a stunning sight. Since the moon moves eastward as it revolves around the Earth, it creeps across the sky to the tune of 12 degrees (24 full moon diameters) each day. That’s one moon diameter per hour. Normally we don’t notice this movement during a single night, but last night was the exception. When the moon lines up with a bright object like a planet or star, its orbital motion is obvious.
Being so close to Jupiter, it was incredibly easy to see how its position changed with respect to the planet and also the nearby bright star Aldebaran. Even 20 minutes sufficed to see a noticeable change in position. When a beautiful halo surrounded the twosome at 11 p.m., the moon had already moved past Jupiter headed east. Cool!
If the weather didn’t cooperate for you last night, another Jupiter-moon conjunction will occur next month on January 21. At around 10 p.m. (CST) that night, they’ll be slightly closer than they were last night. After that, we’re pretty much done for the year. There’s a conjunction in March but it won’t be nearly as tight.
Tomorrow we’ll look back at 2012′s celestial highlights and then preview the coming year.