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Astronomy Picture of the Day

Maine sunset

Photo of the Week.. The setting Sun illuminates the rocky coast of the US state of Maine. Photo by Lauren Brewer.

Astronomy news for the short week starting Sunday, August 23, 2002.

Skylights now resumes its normal schedule.

We lose the evening Moon this week, as our companion wanes through its gibbous phase on its way to third quarter next Friday, August 30. It passes through apogee, where it is farthest from the Earth, about in the middle, on Monday the 26th. Climbing north along the ecliptic, the Moon crosses the celestial equator at about the same time, heading for Taurus, where Saturn resides.

The evening sky now holds but one obvious planet, Venus, easily seen rather low in western evening twilight, the planet still brightening as it gets closer to the Earth. Still moving eastward against the starry background, Venus is taking a bead on Spica in Virgo, and will make a close pass to it the end of the month. The morning sky holds more, both Saturn and Jupiter. Saturn, ever so slowly moving to the east against the stars, is now close to Zeta Tauri, the star that makes one of the outstretched horns of the zodiacal Bull. Jupiter, on the other hand, has shifted over from Gemini into the next constellation of the Zodiac, Cancer, a dim figure that contains one outstanding treasure, the Beehive Cluster. Saturn is now rising just after 1 AM Daylight Time, while Jupiter follows some time later, rising about 4 AM, before twilight begins to brighten the eastern sky. Just look for the brightest thing you can see. In a dark sky, let Jupiter draw your eyes to the Beehive, which will be just to the northeast of the bright planet.

Going from bright to dim, really dim (800 times fainter than the human eye can see alone and 250 times fainter than Neptune), Pluto begins retrograde motion on Tuesday, the 27th. Highly inclined to the ecliptic, the outermost of the planets now lies well off the ecliptic, even the Zodiac, against the stars of southern Ophiuchus (the Serpent Bearer). A curious body, it is trapped by Neptune in a gravitational "resonance," Pluto going around the Sun twice for every time Neptune orbits three times. Pluto keeps moving in and out of "planet" status. In fact, it is a fascinating body that appears to have been stuck in some kind of transitional state between the huge host of comet cores that lie in a thick disk (the Kuiper belt) beyond Neptune, and a major planet like Neptune itself. In a sense, Pluto is a planetary core, a body that would have been a planet, accumulating from huge numbers of primitive cometary bodies, but ran out of raw material.

People in mid-northern latitudes will see the squarish head of Draco the Dragon to the north of the overhead point in early evening. Draw a line to the south, and it will pass just to the east of Ophiuchus, indeed into the eastern half of Serpens, the Serpent, who wraps tightly about the Serpent Bearer.

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