Astronomy news for the week starting Friday, March 10, 2000.

The next Skylights will appear Sunday, March 19. During this extended Skylights period, the Moon will pass through first quarter the night of Sunday, the 12th, just around the time of moonset in North America, and then wax through its gibbous phase toward full. With the Sun near the vernal equinox, the third quarter will appear near the summer solstice in Gemini, making it the highest, and earliest rising, first quarter of the year. (Observers in the southern hemisphere will see the reverse, the lowest first quarter.) Confusing to beginners, "quarter moon" refers to the same lunar aspect as "half moon." The terms mean different things, however; "half moon" refers to the lunar appearance (half the lunar disk in sunlight), while "quarter moon" refers to the quartering of the orbit. Full Moon, opposite the Sun, is therefore "second quarter," though the term is never actually used. The Moon begins our week up and to the left of Saturn, then plows through the stars of Taurus, the night of Sunday the 12th appearing to the east of the Hyades.

The morning of Wednesday, the 15th, sees little Mercury in conjunction with its much brighter sister planet, Venus. The two are now so low in the morning twilight southeastern sky, however, that only Venus will be readily visible. Even Venus will not be visible for too much longer as it steadily descends into sunlight. The day before, the waxing Moon passes perigee, when it is closest to the Earth.

The evening sky still revels in brightness, great Jupiter shining in the west, dimmer Saturn up and to the left of it, and Orion and its companions swinging to the west of the celestial meridian (the sky's north-south line). Between the evening and morning, Pluto, lying far above the ecliptic among the stars of southern Ophiuchus, begins its western retrograde motion, though not many will watch, as the littlest of planets is 800 times fainter than the human eye can see without a telescope. Only about the size of the collected western states, and 30 times farther from the Sun than Earth, Pluto sends very little light back to us. So little sunlight heats it that the temperature at best is a chilly -387 degrees F (40 centigrade degrees above absolute zero). It is so cold that some of its very thin atmosphere falls to the ground as a snow made of frozen nitrogen, carbon monoxide, and methane. Very similar to Neptune's large Moon Triton, which orbits Neptune backwards and is almost certainly a captured body, Pluto is caught by Neptune as well, orbiting the Sun twice for every three of Neptune's years.
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