Jupiter

Stargazing for 2008 ends with the best sky show of the year--a spectacular three-way conjunction of Venus, Jupiter and the crescent Moon.

At the end of the day, when the sunset is deepening into night, step outside and look southwest. You'll see Venus and Jupiter sitting side-by-side through the twilight. Venus is absolutely brilliant and Jupiter is nearly as bright as Venus. Dec. 1st is the best night of all for the conjunction. The crescent Moon moves in close to form a triangle with Venus and Jupiter. The three brightest objects in the night sky will be gathered so tightly together that you can hide them all behind your thumb when held at arm's length.

With winter fast approaching and the temperatures dropping faster than the remaining leaves, December’s Full Moon is known as the Cold Moon. The Moon will be full this month on December 12th with the New Moon falling on the 27th. But the Moon is not the only bright object in the sky this month.

The planet Venus is visible in the western sky just after sunset. Because Venus orbits the Sun closer than the Earth, it takes Venus less time to complete an orbit. One Venus year is 225 days long. Since Venus is now catching up to the Earth in its orbit, it appears to grow closer and closer to the Sun in our sky. This will make Venus set steadily earlier throughout the month, close and closer to sunset.

The largest planet in the Solar System, Jupiter's cloud tops act like a giant mirror, reflecting much of the sunlight that falls onto them. Some of this reflected light makes its way back towards Earth, making Jupiter appear as the brightest object in the southern sky this month. Through a good pair of binoculars it is possible to see the four largest moons of Jupiter; Io, Europa, Ganymede, and Callisto. Jupiter is slowly making its way toward the southwestern horizon where it will set near the end of the month. On Dec. 1st Jupiter passed very close to Venus and on the 30th and 31st it will appear to pass very close to the planet Mercury, which is only visible for about five days. This conjunction will occur very close to sunset and close to the horizon so make sure there are no trees or buildings blocking your view.

The constellations Pegasus and Andromeda will pass directly overhead in the nighttime sky as December progresses. In Andromeda lies the Andromeda Galaxy at 2.5 million light-years away. It is the farthest object visible to the naked eye. Rising in the east this month is the constellation Orion the Hunter, with its telltale three-star belt in between the bright red supergiant star Betelgeuse, meaning "armpit", and the bright blue star Rigel. Below the belt of Orion is the Great Orion Nebula, plainly visible through binoculars. If you draw a line through the three-star belt and continue the line to the right it will lead you to the star Aldebaron, the brightest star in Taurus, the Bull.

Close to Aldebaron is a cluster of star called the Pleiades, sometimes called the Seven Sisters because seven is the most stars the human eye can see without binoculars.

To hear more stories of the seasonal sky, join us at the Rauch Planetarium for Skies Over Louisville: The Seasonal Edition on the first Saturday of every month at 9 p.m.