November 6, 2005
November Astronomy Notes
The skies this month start off with some wonderful stargazing opportunities, with clear skies, evenings not yet frigid, and thin moonlight. The Milky Way streams east to west (west to east?) and a couple planets are very bright and obvious.
November starts off with with the classic, "End of Ramadan" Cresent Moon-and-Venus configuration in the western sky. This is such a beautiful configuration, I don't know why it doesn't hold a larger place in Western or Native American cultures. Venus is hugely bright, thus it is interesting to know that it is in only a "half-Venus" phase(Like a half-moon.)
Also in the evening sky, but 180 degrees away in the eastern sky, is a very bright orange Mars. It is at opposition on 7 November, which means for us that it will be up from dusk till dawn. It is roughly half way through its retrograde motion. It will remain big, bright, and orange all month, but will become noticably dimmer as the month progresses, becoming less bright than Sirius by December. Anyhoo, until then, even a modest telescope wil reveal the large, triangular dark area of Mars called Syrtis major.
Meteor activity is generally good this month. The Taurids, note for good fireballs, continue this month, peaking about
12 November. Leonids and Alpha Monocerotids are also significant, but covered by glare from the moon.
Lets talk a bit more about the Milky Way. Our solar system is located about midway out from the center of the Milky Way in a spiral arm. The Milky Way that we see is the disk of the galaxy. The planets surrounding the Sun circle around it in roughly the same orbital plane, sweeping out a disk as they go. This disk is, in turn, tilted at a steep angle to the disk of the Milky Way galaxy. As a result, the Milky Way appears to rotate around in the night sky as the year goes by. Since the Solar System is not tilted exactly at 90 degrees, we get a better look "above," or "North" of the disk of the Milky Way in Springtime, and "South" of the disk in Autumn. These are called the North and South Windows. So, in November, we get a good look out the South Window, out of and beyond the Milky Way, toward other members of the Local Group of galaxies to which Milky Way belongs, such as Andromeda.
We still have to look through the stars that share our arm of the Milky Way, so it's not like the window is star free. In fact, in most of the sky, there are enough stars to completely overlap and cover the sky. So why isn't the night sky as bright as the day sky? The short answer is: dust. The universe is dusty; dusty enough to dim or block the light from all those stars. It may help to appreciate the vastness of the universe to know that, in spite of outer space being so empty that it is considered a vacuum, there is still enough dust across the miles to block the light of billions of suns.
Posted by hargers at November 6, 2005 7:42 PM