Minnesota Starwatch for October 2005
[Starwatch Logo]

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 October 2005

Hello, this is Minnesota Starwatch for October 2005. The eastern sky early in the evening is 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 stretching 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 (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. The NASA Spitzer Space Telescope ( http://www.spitzer.caltech.edu/. ), an infrared observatory that was launched on August 25, 2003, is returning stunning images of stellar nurseries that are similar to M42.

Betelgeuse ("The Arm-pit of the Giant"), 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!

October is a good month for planet watching. Venus, the "Evening Star", will be brilliant and high in the southwest well past twilight. On October 16, the bright (1st magnitude) star Antares will be just south of Venus (roughly the width of a finger at arms length). Jupiter will be just visible in early October very low in the west immediately after sunset. Mercury is also faintly visible (a challenge with binoculars) 1-1/3 degrees south of Jupiter on the evening of October 5. Mars will be in an excellent position to observe during October and early November as it will be quite bright (indeed it will not be this bright for another decade). Mars rises in early October as twilight begins in the eastern sky. Mars, distinctive for its reddish appearance (sometimes pumpkin orange), will be in the constellation of Taurus throughout the late-autumn observing season. Near the 1st of October, Mars will be 10 degrees (roughly 1 closed-fist at arm’s length) from the Pleiades (The Seven Sisters), and then begin its retrograde (westward) motion relative to the background stars. For those with small telescopes, the angular diameter of Mars will increase from 18 arcseconds to 20 arcseconds as the separation between the Earth and Mars closes to roughly 69 million kilometers of 0.46 astronomical units at opposition. The Moon is full on the 18th , with Mars rising below it at dusk, while the last-quarter Moon will lie just above Saturn at dawn on the 25th .

For fun Astronomy Outreach programs check out our Public Outreach link, or if you're interested in how you can help build the new Minnesota Planetarium, please call 612-630-6151 or visit http://www.mplanetarium.org.

Como Planetarium is offering fun family shows about astronomy on a limited basis; please call 651-293-5398 for more info! This has been a Minnesota Starwatch produced by the University of Minnesota Astronomy Department.