Skylights featured on Astronomy Picture of the Day

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Full Moon

Photo of the Week. Full Moonset. See it closer-up, then watch it go below the horizon. (These images have been added to Moonlight.)

Astronomy news for the week starting Friday, July 23, 2010.

The week of the full Moon is upon us, the phase passed the evening of Sunday the 25th about the time of Moonrise, allowing a near-perfect full Moon to be seen. The only time a really perfect full phase is witnessed, however, is during a total eclipse, with the Moon exactly opposite the Sun. This one passes a bit north of the Earth's shadow. We then have a couple days of the waxing gibbous phase before full, followed by a bit more of the waning gibbous to take us out of the week. There are no fine planetary passages this week, though we will see the Moon slowly approaching Jupiter. It does, though, pass apogee, where it is farthest from Earth, the night of Wednesday, the 28th.

The wonderful string of western evening planets, though enhanced by Mercury, is slowly fading into the sunset. The little one (Mercury) lies low in twilight at the right-hand (northern) end of the parade, while up and to the left of it is obvious Venus , then farther up Mars and Saturn , the red planet slowly catching up with its far more distant companion, the two anticipating their conjunction on August 1. But look early and with a good flat horizon, as Mercury sets quickly in bright twilight, followed by Venus shortly after twilight comes to a close. Less than half an hour later, Mars and Saturn go down as well.

At the same time, though, giant and very bright Jupiter rises due east, around 11 PM Daylight time. Among the fainter stars of western Pisces, to the south of the Great Square of Pegasus, Jupiter dominates the late night and morning skies, shining far brighter than any star. On Friday the 23rd, Jupiter stops its normal easterly motion and begins to move backwards ( retrograde), the result of the Earth's starting its passage between Jupiter and the Sun.

The coming month of August is known for its Perseid meteor shower. But July has one too, though of lesser rank. Mid-July marks the beginning of the Delta Aquarids, which stretch across the month and into August, one portion even into September. With luck and a dark sky you may catch one or two in the late morning hours.

Oddly, though by coincidence, the three brightest stars -- Sirius (Canis Major), Canopus (vel-p.html">Carina), and Alpha Centauri (Centaurus) -- are in the southern sky, with only Sirius readily visible from northern climes. Numbers 4 and 5, and 6, though -- Arcturus (Bootes), Vega (Lyra), and Capella (Auriga) -- are in the north. This is a fine time of year to admire the first two of these, orange Arcturus in the evening's west beneath the Big Dipper and (just a hair fainter) white Vega climbing the northeastern sky as Arcturus descends.
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