| Aug 04, 2005


Night Skies, August 4, 2005

Night Skies August 4, 2005

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The Night Skies of August:A Convergence of Planets and a Shower of Meteors

by Leo Enright

In the month of August, with longer nights than in July, we have more time to enjoy the view of the great Summer Milky Way, as well as the famous meteor shower of mid-August. This year we have the added bonus of the two brightest planets steadily converging in the western evening sky.

At the beginning of the month, sunset in this area is at about 8:30 p.m. Eastern Daylight Time, and evening astronomical twilight ends at about 10:30 p.m. By the end of August, sunset will be at about 7:45 p.m., with twilight ending at about 9:30 p.m.

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Late summer sky watchers who are fortunate enough to have dark, rural skies can really get to know the Summer Milky Way and the constellations within it. Just let your late-evening gaze sweep from the northeast to the southern part of the sky. In the northeast, entirely within the Milky Way, you see Cassiopeia, in the shape of a very large letter W. High in the east you notice Cygnus, the Swan, also called The Northern Cross from the shape of its star pattern, and down in the south, in the richest and densest part of the Milky Way, is Sagittarius, whose star pattern forms the shape of a teapot with the handle to the left and the spout to the right. This Summer Milky Way is really one arm of our home galaxy, the Milky Way Galaxy, and our immense solar system, with the Sun, its nine planets and all their many moons, is really just a small dot among the 200 billion stars that make up this galaxy, which is over 250,000 light-years in diameter!

During August we also have a chance to see the famous Andromeda Galaxy, the only other galaxy that can be seen with the unaided eye. This close neighbour of our galaxy is one of the largest members of the local group of over a dozen galaxies, and it is only (!) about 2 million light-years away. To find it, locate the W of Cassiopeia well up in the northeastern sky at about 11:00 p.m. Trace a line from the right side of the W down and to the right toward the eastern horizon. About half way along that line, you should see a faint fingerprint on the sky. That is it. Remember that what you are seeing is another whole galaxy made up of 400 billion stars, and that the light from them has taken over 2 million years to reach your eyes!

Among the bright planets, the two brightest of all do a great converging act this month. Brilliant Venus in early August is easily found low in the western sky between 30 minutes and 90 minutes after sunset. The second brightest planet, Jupiter, is somewhat higher but in the southwestern sky. At the beginning of August, they are 30 degrees apart, that is 3 times the width of a fist held at arms length. Each evening they appear closer to each other by 1 degree, that is, by about the width of a persons little fingernail held at arms length. Remarkably, at dusk on August 31, these two brightest planets will appear almost on top of each other. It should be a fine reminder of the Venus-Jupiter convergence of February, 1999. Of course, they are not physically near each other, since Jupiter, with an orbit that is far outside that of Earth, is actually 5 times further way from us than Venus. The third evening planet, reddish Mars, may be seen rising in the east at about midnight in early August, and thence rising 2 to 3 minutes earlier each evening, until by months end it will be seen about 10:30 p.m. Mars is gradually brightening, and, if inspected in a small telescope, appears larger over the course of the month. Saturn and Mercury, which were seen low in the western evening sky in the month of June, are not visible in the first half of August, but in the last two weeks of the month they may be seen very low in the eastern sky between 60 minutes and 30 minutes before sunrise. As was the case in the western sky two months ago, they are both again below Castor and Pollux, the brightest stars in the constellation Gemini. Saturn appears above; Mercury is below and to its left. Over the last 10 days of the month, Mercury becomes considerably brighter than Saturn, but remember that a good view of the eastern horizon will be needed to see this planetary pairing in the morning sky.

Several beautiful lunar-planetary arrangements are to be seen this month. On the evening of August 7, do not miss the sight of the slim crescent moon just to the right of Venus and low in the western sky about 40 to 50 minutes after sunset. At the same time on the evenings of the 8th and 9th, the crescent moon will be seen marching between the converging planets Venus and Jupiter, and on the 10th it will be to the left of Jupiter. At about midnight on August 24th the rising moon will appear to the left of Mars, and again about midnight and after on August 25th it will appear close to the Pleiades star cluster. In the morning sky about 40 minutes before sunrise on August 31st, the thin waning crescent moon will appear above Saturn, and at the same time on September 1st, the very thin crescent moon will appear below Saturn.

With the famous Perseid Meteor Shower reaching its absolute peak during the day of August 12, Thursday and Friday August 11th and 12th should be almost equally good for observing this annual event which has received its name because these meteors (sometimes called shooting stars) all seem to radiate from a point in the constellation Perseus which is in the northeastern evening sky below the Wof Cassiopeia. With a First Quarter Moon setting about midnight or before on those evenings, there will be no lunar interference at all after midnight, and so, amateur astronomers are looking forward to spectacular meteoric fireworks, especially from midnight to dawn on both of the peak nights. If the weather cooperates, many skywatchers will be observing all night, keeping an hour-by-hour count. If the weather is uncooperative on the peak nights, remember that the Perseids are somewhat active for several weeks before and after their peak. To see the most meteors possible, face in a northerly, or a southeasterly, direction, and direct your gaze to a quarter-section of the sky quite high above the horizon. Most of the meteors are very fast, and are coming from a spot, called the radiant, in the northeastern part of the sky. Do not despair if you have 10 minutes without seeing any; in the next 10 minutes you may see 20 of them, since they often come in clusters. I would be interested in hearing from local observers about their per-hour counts of Perseids for various times during both of the nights mentioned.

Those who are interested in more information about observing stars, planets, and meteor showers throughout the year should obtain a copy of the book, The Beginners Observing Guide, which is now available at Sharbot Lake Pharmacy.

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