Skylights featured on Astronomy Picture of the Day

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Skylights featured nine times on Earth Science Picture of the Day: 1 2 3 4 5 6 7 8 9


Photo of the Week. Occluded sunrise.

Astronomy news for the week starting Friday, July 17, 2009.

We begin the week with the Moon in its waning crescent phase as it heads towards new on Tuesday, July 21. It will first become easily visible as a western-sky waxing crescent the twilit evening of Thursday the 23rd. The day of new Moon also sees the Moon passing through perigee, where it is closest to the Earth.

We also begin with the waning crescent within a glorious setting of planets. The morning of Saturday the 18th, the Moon will make a beautiful triangle with the Taurus's Pleiades and Mars , the Moon down and to the left of the cluster and just up and to the left of the red planet. Below them both will be brilliant Venus, and to the right of Venus (and below Mars), the Hyades cluster with Aldebaran (which is not part of the cluster). Note both the similarity in, and the slight difference between, the colors of Mars and Aldebaran. By the following morning, that of Sunday the 19th, the Moon will have shifted down and to the left, and will appear directly left of Venus and to the right of Elnath (Beta Tauri), the star that makes the western horn of the celestial Bull.

New Moon and perigee combine to produce a magnificent total eclipse of the Sun on Tuesday the 21st. (If the Moon is closer to apogee, it is too far away to fully cover the solar disk and we get an "annular" eclipse.) Unfortunately, it's not for us. The path of totality, the full shadow of the Moon, will pass across northern India and southern China then out into the mid-Pacific Ocean. The partial eclipse (the Moon taking a bite out of the Sun) covers much of Asia, but Europe and the Americas will be left out entirely as, for these lands, new Moon occurs at night.

Back to the morning sky. Mars rises ever earlier, and is now up (moving between the Pleiades and Hyades, as noted above) by 2 AM or so Daylight Time. Less than an hour later, up comes Venus, which is now rising about as early as possible during this orbital round. Though beginning to rise later, Venus will be visible during most of the rest of the year. While the morning holds the two planets that bracket the Earth, the evening is now the domain of the two giants. Jupiter unmistakably rises in the southeast in late evening twilight, about an hour before Saturn sets in the west.

With the Moon dimmed out, we can take an evening look at the fainter constellations. About three-fifths of the way from orange Arcturus (to the south of the handle of the Big Dipper) to bright white Vega (nearly overhead and to the northeast of Arcturus), find the box that makes the "Keystone" of Hercules, the rest of the constellation seen to the north and south of it. Directly south, above reddish Antares (of Scorpius), is the huge distorted pentagon that makes Ophiuchus, the Serpent Bearer, the giant snake depicted by two streams of stars the run to his left and right. Serpens is the only constellation that comes in two parts.
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