Feature Article October 2, 2002
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Jupiter replaces Venus as the dominant planet On the last Sunday of October, we will return to Standard Time, and so, in the last week of the month, our nights will seem to be longer, with sunset actually being before 5 p.m. and the end of twilight just after 6:30 p.m. STANDARD Time.
In October the great Milky Way still sweeps overhead in the late evening. This enormous band of light is the starlight from billions of stars in our home galaxy, our sun being just one of those billions. Sky watchers who have observed the Milky Way for the last several months know by now that it contains three very distinctive constellations: Cassiopeia, in the shape of a large letter W which is now high in the northeast, Cygnus, the Swan, also called The Northern Cross from the appearance of its star pattern which is now further west from the overhead position it occupied last month, and Aquila, the Eagle, which is now in the south-western sky. Low in the south where the teapot of Sagittarius was seen last month, we find the constellation Capricornus, the Sea-goat (or the Goat-fish) a very strange, amphibious creature from an ancient myth. To the modern stargazer, this enclosed V-shaped pattern looks more like the hull of a large boat viewed from the front. The three very bright stars of the Summer Triangle are no longer straight overhead in the evening sky; in fact, Deneb, brightest star in Cygnus, Altair in Aquila, and Vega in Lyra are now the three brightest stars in the western half of the sky. Meanwhile, the bright stars of the winter season are moving up in the eastern sky, led by the famous cluster the Pleiades, sometimes called The Seven Sisters and riding on the back of the bull, Taurus. On clear nights in October, the outline of Orion, the Great Hunter, can be seen rising before midnight. He will soon be followed by many other stars of winter.
As for the bright planets that can now be seen, the situation is far different from the spring, when all five bright planets dominated the evening sky. This month, only Venus may be seen in the west after sunset, and though extremely bright, it is now so low that few people will see it for more than the first week of the month, and then only if they look in the western horizon about 30 to 40 minutes after sunset. The planet Venus will now disappear for a couple of months, as its orbit carries it between the sun and earth, making it difficult to see because of the glare of the sun. Saturn is easily visible in the eastern sky, by midnight in early October, and two hours earlier by late October, appearing above the hunters head in the constellation Orion. Brilliant Jupiter rises in the east, also, well after Saturn, over an hour after midnight in early October, and before midnight in late October. It is in the constellation Cancer, not far from the naked-eye Beehive Cluster of stars, and its brightness makes it the dominant object in the eastern sky from its rising until morning twilight. Mars and Mercury are difficult, and almost impossible to see. For those who have a good view of the eastern horizon, reddish Mars rises due east at about 5 a.m. and remains low in the eastern sky until it fades into the brightening twilight. Mercury is found rising in the east, also, a few minutes after Mars, and though it remains lower than Mars, its orbit carries it upward until the two are very close on October 10; thereafter they appear to move further apart once again.
On the first five days of the month, early risers will have a chance to see the waning crescent moon move past three planets in the eastern sky. On the morning of October 1, the crescent is above Jupiter; on the 2nd it is to the left of Jupiter, a pairing that should not be missed; on the 3rd it is to the left of Regulus, the brightest star in the constellation Leo; on the 4th, it is above Mars; and on the 5th it is extremely thin and to the left of Mars and Mercury. (Binoculars may be necessary to catch this challenging trio!) Try to catch as many of these early morning views as possible. Another sight not to be missed: on the evening of October 25, careful observers who see the moon shortly after it rises (about 8:40 p.m.) will notice that Saturn is nearby and that, as the night passes, the moon moves closer to the planet -- good evidence that the moons orbital motion can be easily detected over the course of a few hours. At about midnight on the 28th, look for a repeat of the suggested morning view for October 1st: the moon has risen above Jupiter. The next night, after midnight on the 29th, look for a repeat of the morning view of October 2nd: the moon is to the left of Jupiter. Against the background stars, distant Jupiter has moved very little; the moon, however, has moved completely around the sky, and is again passing Jupiter just as it did 27 days earlier.
The annual Orionid Meteor Shower, derived from particles left in the inner solar system after the passages of Halleys Comet, reaches its peak on the night of October 20 - 21, but the bright moon that night may interfere with seeing. Try to observe them in the two weeks before or after, when the numbers may not be so great, but there will be less interference from the moon. Remember, also, to glance northward each night for the chance of seeing a great auroral display, such as we had on three occasions in September.
The Beginners Observing Guide, available at Sharbot Lake Pharmacy, contains star maps and more information about the autumn sky. Clear dark skies for good observing!
