Minnesota Starwatch

University of Minnesota

Department of Astronomy

Minnesota Starwatch for March 2005
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Starwatch Newsletter

Minnesota Starwatch is a newsletter describing the night sky in the Midwest.

It is updated monthly, and is produced by the
Department of Astronomy, University of Minnesota
116 Church Street SE, Minneapolis, MN 55455

Minnesota Starwatch for March 2005

Hello, this is Minnesota Starwatch for March 2005. The western sky early in the evening is still dominated by the spectacular, rich constellations of winter. Most prominent among these is the hourglass shaped constellation of Orion, the Great Hunter. As he has for aeons, Orion pursues his prey,Taurus the Bull, who is fleeing westward. Three bright stars across the center of the hourglass define Orion's belt. At the tip of the sword that hangs from the belt is Messier 42, one of the most active star formation regions in our Galaxy. M42, popularly called the Orion Nebula, is spectacular when viewed through a small telescope or binoculars. You should be able to pick out the four hot young stars of the Trapezium, surrounded by a large greenish gaseous nebula. Three more hot young stars can be seen just to the southeast of the Trapezium. You can view a remarkable three dimensional visualization of the Trapezium and the surrounding nebula at http://vis.sdsc.edu/research/orion.html. This visualization was produced by a collaboration of scientists at the San Diego Supercomputer Center and the American Museum of Natural History Hayden Planetarium. Another young stellar cluster with seven bright members, the Pleiades (The Seven Sisters), will be high in the western sky just after sunset. This young open star cluster is another excellent viewing target for binoculars or a small telescope. Meanwhile, the new NASA Spitzer Space Telescope (http://www.spitzer.caltech.edu/. ), an infrared observatory that was launched on August 25, 2003, continues to return stunning images of stellar nurseries that are similar to the Pleiades and M42. The most recently acquired example is the study of the giant star-forming cloud of gas and dust called the Trifid Nebula. (See http://www.spitzer.caltech.edu/Media/releases/ssc2005-02/ssc2005-02a.shtml. and http://www.spitzer.caltech.edu/Media/releases/ssc2005-02/ssc2005-02b.shtml). The Trifid is located 5,400 light-years away in the constellation Sagittarius which will be peeking above the horizon in the southeast at sunrise by the end of the month.

Betelgeuse, the reddish star that defines the northeast corner of the Orion hourglass, is a swelled-up star called a red supergiant. This is a phase that massive stars enter when they exhaust the hydrogen fuel that sustains their heat during most of their lifetime. When Betelgeuse reaches the end of its supergiant phase, sometime within the next few million years, earthlings will be treated to a spectacular sight as it erupts in a supernova explosion. The explosion, caused by the rapid gravitational collapse of the fuel-exhausted core, will cause Betelgeuse to become 10 billion times as luminous as the sun, and even at earth it will approach the full moon in brightness! Within a year, the ejected shell will be big enough to be seen easily with a small telescope, and the explosion will be seen reflected off the nearby Orion dust clouds for many years. Of course, since Betelgeuse is 540 light-years away, the explosion will not be seen on earth until the year 2544 even if it were to happen tomorrow!

Only four of the five bright classical planets can be viewed during March. Venus, at superior conjunction (on the far side of the sun) on March 31st, will be too close to the sun to view all month. Jupiter, rising early in the evening, will therefore be the most brilliant object in the sky all night. Saturn, whose rings are now tilted so that they appear at slightly less than their maximum opening angle, will be very high in the sky just after sunset and can be viewed most of the night. Mercury will climb rapidly into view after March 1st, and will reach maximum elongation from the sun on March 12th when the separation will be 18 degrees. The moon is new on March 10th, so viewing of Mercury should be excellent during the final days of the rise to greatest elongation. During this time, it will be a bit brighter than Vega, and you can watch its phase change from almost full to less than half-lit if you have a small telescope and can see near the horizon. Mars, the "red planet", can be seen rising in the southeast at dawn. The sky should be nicely dark for the minor Gamma Normid southern hemisphere meteor shower on March 13th. A waning moon will drown out all but the brightest of the Virginid meteors during the last week of March.