Skies Over Louisville: February 2009

Saturn (Hubble Heritage)

The winter solstice is behind us, and our days begin offering us more and more sunlight. But the nights are still dominant, and the cold clear nights offer some great observing opportunities. The full moon occurs on the morning of February 9th. This month's full moon is called the Snow moon. However, it also goes by the name the Hunger Moon because ancient people often had difficult times obtaining food in February.

The highlight of the evening sky this month is the planet Venus, shining brightly in the western sky after sunset all month long. Venus is the brightest object in the night sky, save for the Moon. It appears especially bright this month because it is at the point in its orbit that carries it close to the Earth. Additionally, Venus' clouds reflect much of the sunlight that falls on them, making it act like a very large mirror. Venus will appear steadily lower in the sky as the month progresses. Because its moves in its orbit around the Sun much faster than the Earth does, from our perspective it appears to get closer to the Sun. Later, as Venus moves past the Sun, it will rise in the morning sky.

Saturn makes its appearance this month at about 10 PM over the eastern horizon. Though dimmer than Venus, Saturn is also very bright compared to most stars because it is a very large and reflective planet. It has a large ring system that spans about 100,000 miles, with about 500 to 1000 rings made of ice and rock. Twice during Saturn's 29-year orbit the rings appear edge-on from Earth. Naturally, when these reflective rings are edge-on to us, they add nothing to Saturn's brightness and the planet appears unusually dim. The rings will be edge-on in September 2009.

The constellation Orion the Hunter holds center stage in the southern sky this month. Orion is marked in the sky by its characteristic three-star belt, which lies between the two bright stars, Betelgeuse, meaning "armpit", and the bright blue star Rigel. Below the belt of Orion, in his sword, is the Great Orion Nebula. Through binoculars this fuzzy patch is clearly visible as the gas and dust cloud that contains a stellar nursery, birthing a litter of young stars.

Orion is our tour guide of the winter sky, pointing us to a host of winter constellations and stories. The Taurus the Bull can be found by connecting the three stars in Orion's belt into a line and continuing that line to the right. This will lead you to Aldebaren, the brightest star in Taurus. By extending the three stars in Orion's belt to the left instead, you will encounter the brightest star in the sky, Sirius, the Dog star in the constellation Canis Major. As Orion's trusty hunting dog, he is also accompanied by Canis Minor, or the little dog. Finally, by drawing a line from Rigel to Betelgeuse and continuing upward you will find a pair of bright stars. These are Castor and Pollux, the two brightest stars in the constellation Gemini.

To see the sky come to life and 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.

To Ask the Astronomer a question, send your email to planet @ louisville.edu.
To listen to the Sky hotline, call 502-852-6664 and press 4 for the Sky this Month.