When the sky is clear on cold January nights, the planet Jupiter shines brighter than the stars.  Step outside with binoculars and you can see up to four of its moons.

These are the Galilean moons, named for Galileo because he was the first to report them in 1610. He used an improved 20-power telescope that wasn’t even as good as today’s birding scopes.  When the moons are in the right position you can see what Galileo saw — something like this.

However on the night of Friday January 23 you’ll need a real telescope to view them because three of the moons — Europa, Callisto and Io — will transit (pass across) the disk of Jupiter and cause eclipses on the planet.

Above, the Hubble Space Telescope captured Io playing “Me and My Shadow.”  At one point on January 23-24 all three moons will play this tune.

Astronomy.com calls it a triple shadow transit.    Click here for their drawing of what you’ll see in the telescope at 1:40am EST on January 24.

This is your last chance to witness Jupiter’s triple shadow transit until 2032, but it’ll take some preparation and luck to see it.  You’ll need a telescope and the sky has to be clear.

In Pittsburgh we’ll have to cross our fingers.  Our sky is usually overcast in winter.

(photo of Io and its shadow on Jupiter from NASA’s Hubble Space Telescope.  Click on the image to see the original)