Cosmic optical illusion? It's a matter of degree

  • Article by: BLAINE FRIEDLANDER , Washington Post
  • Updated: January 20, 2013 - 7:56 PM

Don't believe your eyes: Jupiter and the moon will look like they're next to each other tonight - a conjunction that won't recur until 2026, scientists say.

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Planet Jupiter, from Voyager 1 space exploration ship

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Take a break from the inauguration hoopla. While dancers sway at Washington's inaugural balls on Monday, the cosmic couple Jupiter and the fattening moon will deliver a waltz of their own: They are less than a degree apart.

Find them nearly overhead on Monday evening in the east-southeastern sky. In fact, they will be at their closest at 10:30 p.m. CST, according to Tony Flanders and Alan MacRobert, editors at Sky & Telescope magazine.

EarthSky.org says this is the closest moon-Jupiter conjunction until 2026.

Jupiter and the moon are not really next to each other, of course -- it will just look that way. The mean distance of the moon is about 239,000 miles to Earth, and the mean distance for Jupiter from the sun is about 483.8 million miles.

The exact time the moon appears closest to Jupiter will be 10 p.m. in the Midwest and other regions of the Central Time Zone. Some parts of South America will see the moon completely block out Jupiter in the sky.

Examining the moon for the next several evenings, one should be able to notice that it's filling out more -- and getting a smidgen brighter. Incidentally, the moon is officially full next Saturday, at 10:38 p.m.

Jupiter's brightness remains constant through the weekend. The planet was a few shades brighter in early December, since it reached a position opposite the sun -- from Earth's perspective. Jupiter and the moon last converged on Christmas night.

If you can find a dark sky, you can catch the moon and Jupiter snuggle between the star clusters Hyades (Messier 25), and the Pleiades (Messier 45). Along with the star Aldebaran, the Hyades loiter underneath Jupiter and the moon, while the Pleiades hang out on top.

For telescope owners: If there are clear skies on Monday, Jupiter's famed Great Red Spot transits the Jupiter meridian at mid-evening at 8:52 p.m. (that's the middle of the transit), according to the Sky and Telescope online Red Spot calculator.

In case Monday night is cloudy, or if you want to see close-ups of Jupiter and the moon from the comfort of your computer, there will be an Internet broadcast live on Slooh.com starting at 8 p.m. Central time.

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