Starwatch Newsletter Minnesota Starwatch is a tape-recorded message describing the night sky in the Midwest, which can be called by telelphone number (612) 624-2001 It is updated montly, and is produced by the Department of Astronomy, University of Minnesota 116 Church Street SE, Minneapolis, MN 55455

Hello, this is Minnesota Starwatch for August, 2001.

This month the Milky Way makes one of its most impressive showings for northern observers. Just after dark it sweeps broadly from the southern horizon to the northern horizon, passing just east of zenith on the way. Cygnus, the Northern Cross, marks the Milky Way's highest point in our sky at this time. Observers looking just above the southern horizon will see two prominent Milky Way constellations. Those are Scorpius, with its long curved tail, and Sagittarius, which is sometimes described as looking like a teapot. The Milky Way represents the collected light of a multitude of stars too faint to see individually, but which together appear brighter than the sky nearby. We live in a large galaxy of stars shaped something like a pair of dinner plates stacked with one inverted, so that their rims come together.

Our sun is located roughly half way from the center of the galaxy to the rim, and near the midplane. From that perspective the galaxy traces a broad ring around the sky, and this feature is what we call the Milky Way. Many of the stars we see are actually much more luminous than the sun. They appear faint partly because they are extremely far away. In addition, the vast spaces between the stars are filled with a very tenuous but dusty gas made from the same kind of material found in the stars themselves. The distances are so vast that even a scant sprinkling of dust obscures all but the nearest stars. In the past few decades astronomers have come to realize that our Milky Way is one of an uncountable multitude of similar galaxies. Using such instruments as the Hubble Space Telescope we are able to find galaxies so distant that the light we see left those galaxies as much as 10 billion years ago. That was long before the Sun was formed as a star and in a time when our own Milky Way was very young. So astronomers see these distant galaxies as objects that might resemble our own Milky Way in its youth.

Looking again with your own eyes at the southern Milky Way, you will find a very bright red object between Sagittarius and Scorpius that is not a regular resident of this part of the sky. This is the planet Mars, which passes through here roughly every couple of years on its path around the Zodiac. Mars was even more prominent last spring, when it made one of its closest approaches to the Earth in many years. Now it is slowly receding and fading as it falls behind the Earth in its orbit around the sun. It remains the brightest object in the evening sky.

The predawn sky is now dominated by the planet Venus, with Jupiter gaining on it over the next few months. In mid month both planets will be prominent in the east, where they will be joined by a waning crescent Moon between August 15th and August 17th. On the 16th the Moon will pass very close to Venus, in fact. That same period corresponds to the peak of the Perseid meteor shower, which is most easily seen after midnight. Sometimes this shower produces spectacular bursts of meteors. Meteors are streaks of light resulting from small grains of material burning up in Earth's atmosphere after being left behind by comets.

The Minneapolis Planetarium offers a wide variety of programs for all ages. For more information, call (612) 630-6150.

For those interested in the Minnesota Astronomical Society, call (651) 649-4861 for information on their upcoming events.

Minnesota Starwatch is available online at http://www.astro.umn.edu/Outreach/pub_out.html.

This has been Minnesota Starwatch, produced by the University of Minnesota Astronomy Department in cooperation with WCCO Weather Center.

Last Updated: Thu Jul 19 20:16:39 2001