SKYLIGHTS

Astronomy news for the week starting Friday, June 10, 2001.

The Moon, beginning the week in its waning gibbous phase, passes third quarter the evening of Wednesday, the 13th, and thereafter wanes through crescent, every day rising later after midnight. It passes south of Neptune, in Capricornus, on Sunday the 10th, and south of Uranus, in the far eastern end of the same constellation, the following day.

The two planets outward from the Earth provide a wonderful contrast. Jupiter, the Solar System's giant, and ordinarily the second brightest of planets, passes conjunction with the Sun on Thursday the 14th, and will be quite invisible. Mars, on the other hand, is now at its best, passing opposition to the Sun the day before, Wednesday, the 13th. On opposition night, Mars will rise at sunset, set at sunrise, cross the celestial meridian to the south at midnight (1 AM daylight time), and have its greatest angular retrograde (westerly) speed. It will also about as close to the Earth as possible during this orbital round, 68.6 million kilometers, or 42.6 million miles. Unfortunately, the red planet, which now shines brighter than any star in the sky (and is now exceeded only by the morning's Venus, the Moon, and the Sun), will also be at about its most southerly position (just to the west of Sagittarius), and for northern observers about as low as it can get. Turbulence in the Earth's atmosphere then makes detail more difficult to view by telescope. After opposition, Mars will begin to rise before sunset, will move more and more into the early evening sky, and will be with nicely us for the remainder of the year. Mars passes opposition to the Sun every 780 days. The orbit is so eccentric that opposition distance vary considerably. The next one will be better. The minimum distance is 56 million kilometers (35 million miles), the maximum almost twice as great. Only Venus comes closer.

Mars actually lies in far southern Ophiuchus between Sagittarius and Scorpius, providing a good chance to compare the color of the planet with its namesake Antares (Ares the Greek version of the war god). As spring slowly blends into summer, these beautiful summertime constellations, which contain the Milky Way, will begin to overtake the more drab spring skies, which now still dominate in the early evening, Virgo and Spica nearly due south as night falls. Watch as they slip away a degree per day to the west as the sky reflects the degree-per-day motion of the Earth around the Sun. If your skies are dark, you might make out the dim box of stars that forms Libra, the scales, the zodiacal constellation that lies between Virgo and Scorpius.