September: sky sights at summer's end: when Vega shines highest overhead, the riches of Sagittarius are highest in the south.
THE TWO BRIGHTEST summer stars are Arcturus, shining in the western sky on September evenings, and Vega overhead. See the all-sky chart on the facing page. One reason they're so bright is that they're fairly close to us as stars go. Arcturus is 37 light-years away, and Vega is 25.
As the chart also shows, Altair is high toward the south-southeast, Antares is getting low in the southwest, and the Big Dipper is dipping down in the northwest. The Great Square of Pegasus is on the rise in the east, balancing on one corner.
The chart also shows the wide, dim, softly glowing band of the Milky Way crossing the sky from low in the south-southwest, up very high across the east, and down to the northeast. At the Milky
Way's highest point, a large brighter patch pools as the Cygnus Star Cloud. It's not delineated on the chart, but it's plain to the naked eye under a dark sky.
In the south, the Milky Way is incomparably bespeckled with star clusters and luminous nebulae in the regions of Scutum, the Shield, and Sagittarius, the Archer. Seemingly buried in the Scutum Star Cloud--but actually thousands of light-years in front of it--shines M11, one of the finest telescopic open clusters in the heavens. Telescopes of 4 to 8 inches aperture show it as an avalanche of pinpoints amid a dim glow of fainter, unresolved suns.
The main star pattern of Sagittarius is called the Teapot, and that's exactly what it looks like. Above and upper right of the Teapot are the main glories of the Sagittarius Milky Way. Under dark skies, the naked eye beholds M24 (the Small Sagittarius Star Cloud) and, just upper right from the Teapot's spout, the Large Sagittarius Star Cloud looking like a puff of steam. Near this are M8, the Lagoon Nebula, and fainter M20, the Trifid Nebula. Near the Teapot's lid is the globular cluster M22. All are fascinating targets for amateur telescopes. Use the photo here to help locate them.
It's no coincidence that Sagittarius is so rich in deep-sky objects and faint stars. When you look this way you are looking toward the center of our Milky Way Galaxy. The rich center itself (off the Teapot's spout) is obscured behind the dark dust clouds prominent in the picture. But even so, in this general direction our line of sight intersects lots of good stuff.
Planets in September
Mercury is very low in bright twilight after sunset and hard to detect. It's least difficult toward the end of the month.
Venus and Saturn are also low in twilight but higher than Mercury, as shown in the scenes at left.
Mars (in Cancer) rises around 3 a.m., far lower left of bright Jupiter shining in the east by then. Mars is dim by comparison. By dawn's first light it's well up in the east, still to Jupiter's lower left.
Jupiter (in Gemini) rises above the east-northeast horizon around the middle of the night like some eerie UFO. By dawn it's blazing very high in the east-southeast. Look off to its left for Castor and Pollux, the head stars of Gemini.
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|Date:||Jan 1, 2013|
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