Skylights featured on Astronomy Picture of the Day

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Skylights featured three times on Earth Science Picture of the Day: 1 , 2 , 3 , 4 .


Photo of the Week.. A deep view of Cygnus, the Swan, has bright Deneb near the upper left, Albireo at lower right, and the Milky Way running between the two.

Astronomy news for the week starting Friday, July 18, 2003.

The Moon wanes through the last of its gibbous phase the early part of the week, then passes through its third, or last, quarter the night of Sunday, July 20, against the stars of Pisces, about the time of Moonrise in North America, the phase near perfect. About a day later, it passes through apogee, where it is farthest from Earth. The remainder of the week sees it waning through crescent as it climbs to the north close to the ecliptic. The morning of Thursday the 24th, the slimming crescent will fall between the Pleiades and Hyades of Taurus, this ancient constellation of the Zodiac now nicely having cleared the rising Sun .

Except for Mars, all the "ancient planets," the ones known from unremembered time, are out of the way and close to invisible. Jupiter sets in mid- twilight, as does Mercury, while rises just as dawn begins, followed by Venus in mid-morning twilight. The stage thus belongs to the red planet, which lofts above the southeastern horizon shortly before 11 PM daylight time. By dawn, it is directly south, dominating the dim stars of southern Aquarius. Though the Earth is slowly catching up to it, Mars still moves along to the east against the starry background. Slowing its pace, the planet will begin retrograde, or westerly, motion against the stars at the end of the month, and will then take about another month to reach ts glorious opposition, when it will be at its closest and brightest since any time in remembered history.

As the sky darkens, those at mid-northern latitudes see the Big Dipper swinging into the northwest, while the Little Dipper stands tall, its two front bowl stars high above Polaris (which nicely marks the North Celestial Pole) at the end of the handle. Between the two curl the aptly named stars of Draco, the Dragon, one of which -- Thuban -- was the pole star in ancient times. To the east of the Dipper, above Hercules, the Dragon's head looks downward, its eastern side nicely lined up along the "solstitial colure," the circle around the sky that connects the two solstices (in Sagittarius and Gemini) and the celestial poles. Ninety degrees away runs the "equinoctial colure," which does the same with the equinoxes (in Pisces and Virgo) and the poles. While the North Celestial Pole has a fine marking star, the South Celestial Pole goes without. At least it goes without for now, as precession, the 26,000-year wobble in the Earth's axis (caused by the pull of the lunar and solar gravity on the Earth's equatorial bulge) will bring Polaris off the northern pole, and will eventually bring fine pole stars to the south.
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