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 -- Full List Restored!


Photo of the Week. Sunset.

Astronomy news for the two weeks starting Friday, May 11, 2012.

The next Skylights will appear on Friday, May 25.

The Moon starts off our fortnight in its third quarter, the phase actually reached the afternoon of Saturday, May 12th, with the Moon out of sight. That morning will provide a fine view of the almost perfect phase. Look for it between the classical figures of Aquarius and Capricornus. The remainder of our first week sees the Moon fading in the east as a waning crescent, new Moon finally passed on Sunday the 20th. The Moon then switches into the west, allowing us to admire the waxing crescent. Be sure to look the evening of Tuesday the 22nd, when the thin crescent will appear just down and to the left of Venus. By the following evening, the thickening crescent will be well up and to the left of the planet. Look early! Earlier in our period, the Moon visits with Neptune on Sunday the 13th (the Moon six degrees to the north) and with Uranus on Wednesday the 16th.

This new Moon will produce an annular eclipse on the evening of Sunday the 20th. (In an annular eclipse, the Moon is a bit too far away to entirely cover the Sun, leaving a ring of bright sunlight. Apogee, where the Moon is farthest from Earth, takes place the day before.) Near sunset, the path of annularity goes from northern California through Nevada and Utah into New Mexico. Only those in the far west get to see all of the annular portion. A large part of western and central US and Canada, however, will witness a partial eclipse, but with the Sun only near or during its setting. Do not attempt to look at the Sun directly without a professionally made filter, or use pinhole projection (shining the sunlight through a pinhole in a piece of cardboard or paper onto a second sheet placed behind it).

Back to the planets. Working our way from inside out, Mercury rises in bright morning twilight and cannot really be seen. Venus, on the other hand, is still bright in the west. But you need now to look earlier, as the planet is preparing to swing between us and the Sun and is therefore setting notably earlier day by day, appearing to plunge toward the horizon. At the beginning of our two-week period, it is still setting around 11 PM Daylight Time. But by the end of it, Venus sets before 10 PM with twilight still lighting the sky. Up until now, Venus has been moving steadily to the east against the stars, more or less keeping pace with the Sun. On Tuesday the 15th, however, the planet reverses itself and begins westerly retrograde motion, which will cause our familiar evening companion to be gone by the end of the month.

Mars, however, is still nicely with us. Fading just a bit as Earth pulls away, the red planet is moving noticeably to the east against the background south of the classical figure of Leo to the southeast of Regulus. Now well past the meridian to the south as darkness falls, Mars sets around 2:30 AM or so Daylight Time. Much farther out, Jupiter makes invisible news by passing conjunction with the Sun on Sunday the 13th. As much as anything, though, the night belongs to Saturn. Distant and moving slowly, the planet continues to hang out to the northeast of Spica, transiting the meridian around 10:30 PM shortly after Venus sets. Saturn is then with us the rest of the night until it sets in dawn's light.

May belongs to the Big Dipper, which rides high in the hours before midnight. The asterism, and the constellation to which it belongs, Ursa Major, the Great Bear, is along with Orion among the sky's most beloved figures. Look at the second star in from the end of the Dipper's handle to find bright Mizar with dimmer Alcor next to it, the two making the Arab's Horse and Rider. Then follow the front bowl stars downward to Polaris, which is at the end of the handle of the Little Dipper and closely marks the north celestial pole. Finally, look to the southwest of the Dipper to find three unrelated pairs of stars that make both the Bear's feet and, in a quite different mythology, the Arab's "leaps" of the gazelle.
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