Jupiter And The Moon – What A Show!

Jupiter and the moon 15 minutes before sunset. The photo captures their appearance in binoculars. Photo: Bob King

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.

The waxing gibbous moon and Jupiter light the way ahead in this picture taken during twilight last night Dec. 25, 2012. Photo: Bob King

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.

By 11 p.m., when a halo circled the duo, the moon had moved off to the east of Jupiter. Photo: Bob King

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.

The closest and arguable the best conjunction of Jupiter and the moon in the coming year happens on January 21, 2013. They two will be only a bit more than one moon diameter apart around 10 o’clock that evening. Created with Stellarium

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.

8 Responses

  1. Wayne Hawk

    Aloha “a.b.”!
    For a few days before Christmas and for almost the entire day, we had one of our infamous “winter storm systems” clouding up Hawaiian skies. Then, around midnight, the clouds began to break up leaving large sections of clear sky! Thanks to being an avid reader of this Website, I looked at the moon and much to my surprise I actually could see Jupiter at the “11 o’clock” position of the moon!
    Again, I had one of those “mind-rushes” thinking just how tiny we are in the grand scope of the universe and what a wonder it is that I could actually see Jupiter by just “looking”. Then I wondered how many folks had looked at the moon and didn’t have a clue as to what they were actually able to see. For those who noticed, I have a feeling they thought it was Venus since that planet is often the one most seen and/or talked about in the evening or mornings. What a shame it was for them not to know.
    Thanks for keeping this site going for those of us who have an interest in what is going on in our vast universe, Bob. This is appreciated more than you know.
    I hope your Christmas was safe and relaxing. Sounds like it was.

  2. Giorgio Rizzarelli

    Thank you Bob for the great pictures. Since on 25th we had overcast I’m enjoying the event through your photos, and those of a friend in South America which, as you certainly know, saw it as an occultation (more are of course on http://spaceweather.com/gallery/index.php?title=jupiter).
    I confirm that Jupiter becomes visible (invisible) at naked eye around sunset (sunrise), with variations according to meteo conditions.
    Thanx for the tip about the January conjunction!

    1. astrobob

      Hi Giorgio,
      Since you live in Italy, you will see different variations on the next several conjunctions of Jupiter and the moon. When I looked ahead, my point of view was “U.S. centered”. It’s fun to see a planet or star when the sun is still in the sky – good sport you know!

  3. thomas s

    howdy Bob, hope you had a very Merry Christmas. The conjunction must have been a special holiday treat. But a question. Read something the other day about a comet (Ison) discovered by Russian astronomers. The claim was that as it approaches the sun this summer, it could rival the light from a full moon in our skies. Is this hype or reality?

    1. astrobob

      Hi Thomas,
      I had a great Christmas with my family. Yes, Comet ISON will probably become a bright sight. Claims of it rivaling the full moon are a little off. When nearest to the sun and visible only with protection, the comet might approach something like -10 to -13. MAYBE. Remember that all this light would be concentrated in its tiny head, so it would look like a brilliant star. Again, it would be so close to the sun that the view would be nothing like seeing a full moon in a dark sky.

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