Skies Over Louisville: May 2009

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Hubble Telescope

The passing of April brings May flowers, in the sky as well as on the Earth. Using the well-known star pattern the Big Dipper as your guide, the constellations in May are very visible and easy to find. The spring also provides comfortable nights temperatures for skywatching. This month promises to deliver a virtual smorgasbord of constellations across the sky. The Full Moon occurs on May 9th. This is known as the Flower Moon because it coincides with the blooming of the spring flowers.

The spring constellations take center stage this month as the Big Dipper, a pattern of seven bright stars in the constellation Ursa Major, the Great Bear, rotates to its highest point in the sky. The Big Dipper is our tour guide to the spring sky. A line drawn between the two leading stars in the bowl of the dipper will point to Polaris, the North Star. Polaris is located in the sky directly over the North Pole on Earth, so as the Earth spins, Polaris appears to not move in the night sky, always in the northern sky. Polaris is also the brightest star in the constellation Ursa Minor, the Little Bear.

The Big Dipper can point us to spring constellations in the southern night sky. Follow the curved path of the handle and "arc to Arcturus", the brightest star in the constellation Boötes, the Herdsman. His task is to shepherd the two bear constellations, Ursa Major and Minor, in their paths around the North Star. If you continue along the curved line from the dipper handle through Arcturus, it will lead to Spica, the brightest star in the constellation Virgo. The appearance of Virgo in the sky was said to bring about the end of the winter and the rebirth of spring. A line drawn toward the southern sky from the two back stars in the bowl of the Big Dipper will lead to Regulus, the brightest star in Leo, the Lion. This constellation is said to represent the Nemean Lion, a mythological beast killed by Hercules as the first of his Twelve Trials.

This month the star Saturn steals the spotlight this month as the only planet visible in the evening and the brightest object in the night sky, save for the Moon. Saturn is located this month between the constellations Virgo and Leo. In fact, if you draw a line between the two brightest stars in these two constellations, Spica and Regulus respectively, this line will pass very close to Saturn. With a large collection of 500 to 1000 rings that span about 100,000 miles, these pieces of rock and ice make Saturn appear much brighter here on Earth. However, two times during Saturn's 29-year orbit around the Sun, these rings appear edge-on from Earth. Naturally, when we see these reflective rings edge-on, they appear to disappear and add nothing to Saturn's brightness, making and the planet appear unusually dim. The rings will be edge-on in September 2009, for the first time in almost 15 years.

Many of the winter constellations set below the western horizon this month. Orion, the Hunter, as well as the constellation Canis Major, Orion's trusty hunting dog, and Taurus, the Bull, are only visible early in May, setting in the evening sky. Canis Minor, the Little Dog, and Gemini with its two bright stars Castor and Pollux remain visible until late May. The winter group will not appear again until next October.

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. In May, it will be the second Saturday of the month, due to Derby.

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.