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


Photo of the Week.. A quiet sunrise, the Sun reflected in gentle waters, begins another day filled with wonder.

Astronomy news for the week starting Friday, April 15, 2005.

The Moon passes its first quarter on Saturday the 16th somewhat before its daytime Moonrise in North America, and then waxes through gibbous as it heads to its full phase next week. Only four hours after it passes the quarter, it also passes apogee, where it is farthest from the Earth.

Tides are caused by both the Moon and the Sun, which act independently of each other. (Their gravity "stretches" the waters of the Earth, so that as our planet rotates beneath the tidal bulge, the water at the shore goes up and down.) At the quarters, the weaker solar tide fills in the lunar, so the tides (called "neap tides") are neither as high nor as low as they are at full and new Moons. Tides are also very sensitive to distance, and with the quarter Moon at apogee, this neap tide will be especially weak.

The night of Friday the 15th finds the not-quite-quarter in central Gemini, just up and to the right of Saturn, the two, along with the constellation's bright Castor and Pollux, making a fine sight. The following night, with the Moon to the east of Saturn, will be almost as good. By the night of Tuesday the 19th, the Moon will have arrived in central Leo. Near the end of the week, the night of Thursday the 21st, the brightening Moon will lie just to the west of Jupiter, which itself is now just east of Porrima (Gamma Virginis) in Virgo. The ringed planet now crosses the meridian to the south well before sunset, and sets around 2 AM daylight time, leaving the morning to Jupiter (which crosses the meridian around midnight and does not set until dawn begins to brighten the eastern sky) and Mars. Slowly brightening, while moving quickly to the east against the background stars, the red planet (along with Neptune, in Capricornus) rises just before 4 AM (Daylight Time). Among the naked eye planets, that leaves us with Mercury and Venus. On opposite sides of the sky, Mercury rises midway through morning twilight and is quite difficult to see. Setting shortly after the Sun, Venus is virtually impossible to find against the bright sky. By next month, it will begin to make an appearance.

Spring chases Orion and Canis Major (with brilliant Sirius) westward. Down and to the left of the Great Dog is the broken ship Argo, which is separated into Puppis (the Hull) immediately southeast of Canis Major, Vela (the Sails) farther to the southeast, and Carina, the Keel, which contains the second brightest star of the sky, Canopus, and extends far to the south, its limit only 15 degrees from the southern pole.
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