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Waning Gibbous Moon

Photo of the Week. The waning gibbous Moon rides low in an arctic morning sky.

Astronomy news for the week starting Friday, August 3, 2007.

The waning gibbous Moon does not have far to go at the beginning of the week before it passes third quarter on Sunday, August 5. It then enters the waning crescent phase for the remainder of our period, allowing the skies to darken once again, which will bring out the stars. The morning of Monday the 6th (night of the 5th) finds the fat crescent rather well to the northwest of Mars, making for ready location of the reddish planet. The following morning, that of Tuesday the 7th, is even better, as the Moon, now to the east of the Pleiades in Taurus, makes a fine triangle with Mars and the cluster. Yet another morning later, that of Wednesday the 8th, finds the Moon rising to the left of Taurus's Hyades. Lunar perigee is passed right at the beginning of the week.

With Saturn, Venus, and Mercury quite out of sight near the Sun, the planetary sky devotes itself to Jupiter and Mars. Jupiter, now crossing the meridian just after sunset, is into the southwestern sky by the time the sky darkens, and sets just after local midnight (1 AM Daylight). It finally ceases its westerly retrograde motion against the background stars the night of Monday the 6th. In southern Ophiuchus to the east of Antares, the planet does not quite make it back over the border into Scorpius before it turns around and heads back to the east.

Mars, rising just before local midnight, occupies the sky with Jupiter for about an hour. Steadily brightening, it passes this week into zeroth magnitude. Only nine stars are brighter. Yet it still pales next to Jupiter, which shines at nearly the minus third magnitude, and is nearly 15 times brighter than Mars.

We are beginning our run up to the Perseid meteor shower, which peaks the morning of Monday, August 13, when you can expect to see 60 to 90 meteors an hour in a dark, moonless sky. Even during our current week you may see a scattered few in the early morning hours.

The Summer Triangle of Deneb (in Cygnus), Vega (Lyra), and Altair (Aquila) is now prominent in mid-evening high overhead and stretching to the south. Look to the southern anchor Altair to help guide you to several small constellations that include Sagitta (the Arrow) just to the north of it, Delphinus (the Dolphin) to the northeast, and Equuleus (the Little Horse) to the west. Aquila is a central figure in the summer Milky Way as the white band plunges southward from Cygnus to Sagittarius.
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