Last modified: Monday, September 1, 2008
Three planets rendezvous in the west
FOR IMMEDIATE RELEASE
Sep. 3, 2008
BLOOMINGTON, Ind. -- Three planets -- Venus, Mercury and Mars -- will put on a show after sunset in September that would be spectacular if it were higher in the sky. For those with binoculars and a clear view of the western horizon, the group will form a tight triangle very low in the west-southwest that will last an amazing 17 days, from Sept. 3 to 19. Those watching in the Southern Hemisphere will have a much better view, for the action will be higher in the evening sky.
If you glance in that direction without binoculars, you'll probably see only Venus. But a lot more will be going on that will be hidden by the bright twilight. Venus will brush past Mars on Sept. 11, followed by Mercury on Sept. 12. On Sept. 19, Mercury will fall back past Mars as the bright white star Spica moves in from the left to form a quartet with the three clustering planets.
Mercury, Mars and Spica will remain close together until Sept. 26, though all three will gradually sink too low to be seen even with binoculars. But Venus will appear a little higher each evening, and by month's end it will set more than an hour after the sun.
Jupiter, the solar system's largest planet, will be highest in the south as evening twilight fades in September. Immediately below the dazzling white object will be the Teapot formation of the constellation Sagittarius the Archer.
Saturn will emerge from behind the sun in the latter part of the month. Look for the yellow planet very low in the east an hour before sunrise, below the constellation Leo the Lion and its bright white star Regulus. Those with telescopes will be able to tell that Saturn's magnificent rings are now tilted almost edgewise to us.
If you're outdoors on a clear September night, you may be lucky enough to see an aurora (sometimes called "northern lights"). These silent ribbons and curtains of light have a colorful beauty that can be fascinating. Auroras can appear whenever the sun is active, but they are especially likely from August to October. Eruptions from the sun's surface hurl enormous amounts of charged particles into space, and when some of these solar particles head in our direction, they cause auroral activity. For details and photographs, see http://www.spaceweather.com/aurora/gallery_01aug06.htm.
You can watch for auroras when they are most likely to happen by checking Web sites such as http://www.spaceweather.com and http://www.sec.noaa.gov/. Sightings of auroras are reported at http://www.spacew.com/www/aurora.html.
The sun will reach the September equinox on Sept. 22 at 11:44 a.m. EDT (15:44 Universal Time), marking the start of fall in the Northern Hemisphere and spring in the Southern Hemisphere. For the next six months in the Northern Hemisphere, the nights will be longer than the days.
The moon will be at first quarter on Sept. 7, full (the Harvest Moon) on Sept. 15, at third quarter on Sept. 22 and new on Sept. 29.