Astronomy news for the week starting Friday, December 1, 2000.

The Moon, beginning the week as a thick evening crescent, passes its first quarter the night of Sunday, December 3, around the time of moonset in the Americas, and then begins its gibbous growth toward full. The vocabulary of astronomy is often perverse, as at first "quarter," we see "half" the sunlit face of the Moon, the other half in darkness. As a result, "half" and "quarter" seem to mean the same thing. "Half," however, refers to the visibility of the lunar disk, whereas "quarter" refers to the quartering of the orbit, of the phase cycle of 29.5 days. From the whole cycle comes our "month," from the quartering, at least in part, the "week."

The week also begins with the Moon passing a couple degrees south of the planet Uranus, now in Capricornus, and the first of the "discovered" planets, found by William Herschel in 1781. Twice as far from us as Saturn (which now is well up in the east at the end of twilight, just up and to the right of bright Jupiter), and only half Saturn's size, Uranus is only barely visible to the naked eye. Currently a bit to the west of Uranus, and half again as far away, 30 times Earth's distance from the Sun, lies Neptune, which requires a small amateur telescope to see. Discovered around 1846 as a result of its gravitational pull on Uranus, Neptune takes 165 years to orbit and will not complete a full turn since discovery for another decade. Finally, at the end of the planetary system is dim Pluto. Only about the size of the western US, Pluto averages 40 times Earth's distance from the Sun (though now it is just beyond Neptune). With a highly tilted orbit that now places the planet in the constellation Ophiuchus, Pluto passes conjunction with the Sun on Monday, the 4th. The Sun, in its inexorable apparent journey around the ecliptic will pick off Neptune and Uranus early next year.

Pluto may be the end of the planetary system, but hardly the Solar System. Around and beyond Pluto lie hundreds of discovered small bodies of the "Kuiper Belt" of comets. The planets seem to have assembled from small bodies, which in turn were created from the accumulation of the dust that surrounded the early Sun. Pluto a transition object, seems to have tried to match its bigger brothers but could not quite make it as a result of the lack of raw material.

Around 7:15 PM, the "equinoctial colure," the north-south-circle that connects the equinoxes and the poles, rides the celestial meridian. Looking to the south from North America, the colure is bracketed by two lonely stars. To the west of the meridian find first magnitude Fomalhaut in Picsis Austrinus, the Southern Fish, while to the east lies second magnitude Deneb Kaitos, which marks the tail of Cetus the Whale, within a "wet" section of sky that includes Delphinus, Capricornus, Aquarius, and Pisces.
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