Beautiful Jupiter-moon conjunction on tap for tonight

A partial halo rings the moon and Jupiter (upper left) last night Jan. 20, 2013. Tonight the moon will sit right under the planet. Photo: Bob King

Ready for another one of Jupiter’s fly-by-night meetings with the moon? Tonight’s pairing of planet and moon will be the closest yet in a series that began last fall.

Observers in North and South America will get the best views at the most convenient hour. At 9 p.m. (CST) Jupiter will be just one moon diameter (1/2 degree) north of the moon and high in the southern sky.

The waxing gibbous moon and Jupiter will be closest around 9 p.m. (CST) together tonight Jan. 21, 2013 high above the constellation Orion. Maps created with Stellarium

Their proximity also means you have the opportunity to watch the moon “move its own diameter” in a hour. With Jupiter as a reference, you’ll easily see the two approach and separate during the evening. And yes, the moon moves a moon-span in about an hour as it orbits planet Earth. Check it out yourself.


Jupiter emerges in real time from behind the moon during the Dec. 25, 2012  occultation seen in Brazil. Credit: Carlos Bella

Sky watchers living across a wide swath of South America will get an extra treat – a Jupiter occultation. Because the moon is relatively close to Earth, its position shifts slightly against the background stars depending on your location. Seen from central S. America, it’s over 1/2 degree farther north compared to the view from northern U.S., putting it on a path to occult the planet. As the moon travels eastward during the night, it will first cover and then uncover Jupiter. Click HERE for a map and list of cities and times where the occultation will be visible.

Simulated view of the moon and Jupiter – with satellites Ganymede (G), Io (I) and Callisto (C) – as seen in binoculars and small telescopes tonight. North is up, west to the right.

Binoculars will show 2 or 3 Jovian satellites tonight depending on magnification and how steadily you can hold them. Through a telescope you’ll see all three plus be able to watch the shadow of Europa pass over the planet’s cloud tops between 9:18 p.m. and 12:52 a.m. (CST). Look for a tiny black pinprick south of Jupiter’s thick South Equatorial Belt (SEB).

A glance skyward tonight is all that’s necessary to witness this delightful celestial drama unfold. Don’t miss it. Skywatchers in the mainland U.S. won’t see Jupiter and the moon snuggled up this close again until Sept. 2, 2016!

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

2 thoughts on “Beautiful Jupiter-moon conjunction on tap for tonight

  1. AstroBob,
    Saw the conjunction in the middle of the night. Very nice ! The joys of a West facing window. How long will the moon and Jupiter be this close (not necessarily as close as yesterday) I seem to remember last year the proximity lasted a couple of weeks?

    • H. Bob,
      They’ll be about one outstretched fist apart tonight and then getting farther away in the coming nights. Next close conjunction like this one won’t happen till Sept. 2016 for the U.S.

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