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.. Star clusters (circled) and variable stars (yellow labels) in Taurus surround and outline a blank area, the Taurus-Auriga dark cloud, a vast dusty cold interstellar cloud complex 460 light years away that blocks background starlight and in which stars are being formed. Here we also look toward the anticenter of the Milky Way, directly away from the center in Sagittarius.

Astronomy news for the week starting Friday, March 11, 2005.

Skylights will next appear on March 25 and will then resume its usual weekly schedule. Thanks for your patience.

The Moon begins the week in a slim waxing crescent phase that will be just visible low above the western horizon in twilight. Watch as the crescent fills out, the Moon setting ever later, the nighttime side glowing with Earthlight, as it approaches then passes first quarter (Earthlight disappearing) on Thursday, March 17. Over the remainder of the fortnight, the Moon waxes through its gibbous phase to full, which will be reached on Friday the 25th.

The Moon will provide a wonderful way of finding Mercury, which is now making a fine near-spring appearance. Look in western evening twilight the night Friday, March 11, for the slim crescent Moon hanging just above the horizon. Mercury, quite bright, will be just to the right of it, the pair having been in formal conjunction earlier in the day. Greatest eastern elongation, when the little planet is at its greatest extent to the east of the Sun, takes place the next day, causing it to linger until twilight ends. For nearly a week around this time, Mercury will make a nice sight if you look shortly after sunset. Be sure you have a clear horizon; binoculars will help.

A week later, the fattening gibbous Moon will make a nice pass through Gemini. Look for Saturn down and to the left of the Moon the night of Friday the 18th and down and to the right of it the following evening, the Moon and Saturn making a lovely quartet with Gemini's bright stars, Pollux and Castor. Saturn now crosses the meridian to the south just as twilight ends, which is when Jupiter (in Virgo) rises in the southeast. The ringed planet ceases its retrograde (westerly) motion on Monday the 21st, when it resumes its normal easterly movement against the background stars (retrograde caused by the Earth swinging between the planet and the Sun). With Jupiter, Mars rules the morning planetary sky, the red planet now rising around 3:30 AM as the Earth slowly catches up with it.

'Tis the Earth again in the news, really Earth and Sun. At 6:33 AM CST (7:33 AM EST, 5:33 MST, 4:33 PST) on Sunday, March 20, about sunrise in mid-America, the Sun crosses the vernal equinox in Pisces, and spring will begin in the northern hemisphere. At that time, the Earth's axis will be perpendicular to the direction to the Sun, the Sun will be overhead at the equator, will rise due east, set due west, and except for the daylight-extending effects of the Sun's half-degree diameter and refraction by the Earth's atmosphere (which lofts the Sun half a degree upward at the horizon), days and nights will be of equal length. The Sun also technically rises at the north pole, and sets at the south pole, throwing the south polar station into ever deepening twilight and finally a 24-hour night. As the Sun gets higher, its rays become more concentrated in an area of ground, and the weather warms. Welcome all to spring.

While the spring stars are coming forth, those of winter linger on. Look into the west northwest of Orion for Taurus, which is highlighted by two marvelous clusters, the vee-shaped Hyades that make the head of the celestial bull, and the Pleiades, the Seven Sisters, said to be pursued by Orion as he treads the nightly sky. Northeast of Taurus is Auriga. On the border between Taurus and Auriga is the "anticenter" of the Galaxy, the direction exactly opposite the Galactic center, which lies behind the great star clouds of Sagittarius.
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