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 horizontal arc passes from the Sun through a bright sundog caused by refraction of sunlight through ice crystal clouds.

Astronomy news for the week starting Friday, February 6, 2004.

This is a week for the fading Moon. Having passed full the morning of Friday the 6th, the just-barely-waning gibbous will rise the night of the 6th just past sunset, and then will rise a bit over an hour later each night as it approaches its third quarter on the morning of Friday the 13th. To the south of the equator, the last quarter will not rise until after midnight.

The night of Saturday the 7th finds the Moon just to the northwest of Jupiter , which provides a fine chance to watch the lunar motion. Moving by its own angular diameter in about an hour, the Moon will approach Jupiter during the night and be almost directly north of it by dawn on Sunday the 8th. That evening will find the lunar disk to the other side of the giant planet. All this action seemingly takes place on the fiction of the "celestial sphere," the apparent globe over our heads. In reality, the Moon is a mere quarter million miles (almost 400,000 kilometers) away, whereas Jupiter (which now rises around 7:30 PM to the south of eastern Leo) is 1800 times more distant.

Not quite two hours after Jupiter rises, Saturn, high in Gemini, crosses the meridian to the south. To the southwest in the early evening lies Mars at the eastern edge of Pisces. Further over, in southwestern twilight, find that gem of the skies, brilliant Venus. While the other planets set earlier each night, Venus, as it approaches the Earth, does the reverse, setting later, now not dropping from sight until almost 9 PM.

Among the most admired of constellations is Taurus, the ancient Bull. High to the south in early evening, it lies between Aries and Gemini, the latter the most northerly of the zodiacal constellations. Taurus is unique in having the two most prominent clusters of stars in the sky. The head of the Bull is made of the nearby (150 light years) vee-shaped Hyades. While Aldebaran, Taurus's brightest star, appears to be within the cluster, it is actually just in the line of sight, somewhat less than half the Hyades' distance away. To the northwest of the Hyades is one of the most famed of all groups, the beloved Pleiades, or Seven Sisters (though only six are commonly seen with the naked eye), which lies almost three times farther away than the Hyades (and thereby spans a much smaller angle on the sky). Not only closer, the Hyades stars are also much older, over half a billion years of age as opposed to 130 million years for the Pleiades (the age determined by the kinds of stars still present). As a result of its relative youth, the Pleiades is filled with bright, massive, blue stars that give it much of its wintery sparkle.
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