Last modified: Friday, October 1, 2004
Total eclipse of the moon in October
BLOOMINGTON, Ind. -- A total eclipse of the moon will be the prime celestial attraction in October, even for those who don't normally watch the night sky. Observers in most of North America and all of South America, as well as western Europe and Africa, will see the full moon's color change from bright silver to dull copper as it passes through Earth's shadow on the night of Oct. 27-28. The event will not be visible in eastern Asia and Australia.
For details about where the eclipse will be visible, see http://sunearth.gsfc.nasa.gov/eclipse/LEmono/TLE2004Oct28/TLE2004Oct28.html.
The total eclipse will last an hour and 22 minutes, at a time in the evening when many viewers in the Western Hemisphere will still be awake. The midpoint of the eclipse will be at 11:04 p.m. EDT on Oct. 27 (3:04 Universal Time on Oct. 28).
The moon will first edge into our shadow at 9:14 p.m. EDT (1:14 UT), but that won't be noticeable at first to casual observers. It will take a while for the moon to darken enough for anyone to see that something unusual is happening. The actual total eclipse will begin at 10:23 p.m. EDT (2:23 UT) and end at 11:45 p.m. EDT (3:45 UT). The moon will gradually regain its normal color as it emerges from Earth's shadow, and finally it will be in the clear once more at 12:54 a.m. EDT (4:54 UT).
The moon's unusual color during a total lunar eclipse is caused by the orange light of sunsets and sunrises around Earth's rim being bent into Earth's shadow by the atmosphere (the same way a prism works). This orange light then reflects from the moon's surface the way sunlight normally does, making the moon appear anywhere from dark red to bright orange.
Weather can have darkening effects on the moon's color during an eclipse, and so can atmospheric pollution of various kinds, such as dust and ash from a major volcanic eruption. So an exact prediction of the moon's appearance is not possible.
The next total lunar eclipse will be in March 2007.
When the sun, moon and Earth line up for a lunar eclipse, there is usually a solar eclipse as well about two weeks before or after. This time a partial eclipse of the sun will be visible in Japan, northeastern Asia, Alaska and Hawaii on Oct. 13-14. For details see http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2004.html.
The Orionid meteor shower will peak on the night of Oct. 21-22. Observers with a clear dark sky can expect to see about 15 meteors per hour, especially in the early morning hours after the moon sets. The Orionids take their name from the familiar constellation Orion the Hunter, which is where they appear to originate. Orion will rise before midnight in the east-southeast, and the number of meteors will increase as Orion gets farther above the horizon. The meteors are dust particles from Halley's Comet, left behind in the comet's orbit. As Earth crosses Halley's orbit, the particles collide with our atmosphere at high speed and are burned up in an instant by friction with air molecules, creating bright streaks in the sky.
Locations of current auroral activity can be seen at http://www.sec.noaa.gov/pmap/. Click on "Aurora Viewing" for tips on when an aurora may be visible in your area. Information about solar and other space weather is available at http://www.spacew.com/. Aurora sightings are reported at http://www.spacew.com/www/aurora.html.
To watch for auroras when they are most likely to happen, sign up for solar activity alerts by e-mail at http://skyandtelescope.com/observing/proamcollab/astroalert/default.asp.
The bright planets will all be in the morning sky during October, visible before and during morning twilight.
Venus will rise three hours before the sun in its familiar role as the bright "morning star" in the east. Early in the month it will be very close to the bright white star Regulus in the constellation Leo the Lion. Venus will quickly move away from Regulus as the days pass, moving downward to meet the giant planet Jupiter.
Jupiter will be barely above the eastern horizon at the start of October, far to the lower left (east) of Venus. Each day it will rise earlier and climb higher before the sky brightens too much to see it, moving upward toward a rendezvous with Venus in the first week of November. By Oct. 31, the two brightest planets will be a splendid sight in the east-southeastern sky an hour before sunrise.
Saturn will rise around midnight and be high in the south-southeast by dawn during October. Escorted by Castor and Pollux, the two bright stars in the constellation Gemini the Twins, the yellow planet will almost form a line with the two white stars above it (north). Most telescopes will show Saturn's rings, tilted toward Earth. On Oct. 26, the Cassini spacecraft that is orbiting Saturn will make its first close pass by the planet's largest moon, Titan.
Mercury will be too close to the western horizon during October to be seen in the Northern Hemisphere, but it will be considerably higher in the west when viewed from the Southern Hemisphere. By month's end, it should be easy to find for observers in southern latitudes.
Mars will be out of sight behind the sun for most of October, emerging into the morning sky shortly before sunrise during the last week of the month.
The moon will be at third quarter on Oct. 6, new on Oct. 14, at first quarter on Oct. 20 and full (when it will be eclipsed) on Oct. 28.