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Astronomy Picture of the Day

Planetary alignment

Photo of the Week.. The planets align in early May. Jupiter shines at upper left. Between the trees, from top to bottom, are Saturn, Mars, and Venus. Auriga, the Charioteer, rules the upper left.

Astronomy news for the two-week period starting Friday, May 24, 2002.

Phone: (217) 333-8789
Prepared by Jim Kaler.

If you like stars, go to STARS: Portraits of Stars and their Constellations, compiled from previous stars of the week. Enjoy photographs of the January 20, 2000 total eclipse of the Moon. Watch planets move against the background stars. See sunsets, rainbows, the Moon and planets, and other sky phenomena in Sunlight.
Skylights will resume its normal weekly schedule on Friday, June 7.

The extended period easily allows for two lunar phase-passages. Full Moon takes place in Libra on Sunday, May 26, about the time of Moonset in the Americas, and with that, about the time of sunrise. After passing through its waning gibbous phase, the lunar disk transits third quarter a week later, the night of Sunday, June 2, after which it will be seen to wane in the crescent phase in the early morning hours. As it goes, it will pass south of Neptune the night of Thursday the 30th, and south of Uranus on Saturday, June 1. This full Moon will see a penumbral eclipse as the Moon moves through the partial shadow of the Earth. Such events are hardly noticeable, as some fraction of full sunlight falls on the entire Moon.

If nothing else, this fortnight belongs to Venus and Jupiter, which highlight the western evening sky. As May comes to a close, Jupiter lies above much brighter Venus, but is quickly closing in on it. On Friday, June 3, the two pass in conjunction in Gemini, but around noon in the Americas. The night of Thursday, June 2, Jupiter will be a bit to the east of Venus, while the following night it will be seen a bit to the west of Venus. At their closest the two will be only 1.6 degrees apart, about three times the angular diameter of the full Moon. The closeness, of course, is but an illusion, as the giant planet is a bit over 4.6 times farther away than Venus, the brightest planet of them all.

In stark contrast, three "invisible" (to the naked eye) events take place. On Monday, the 27th, Mercury passes inferior conjunction with the Sun, when it between us and the Sun (though not enough in-between for a passage across it). Then on Monday, June 3, just before Venus and Jupiter come into conjunction, Uranus begins its retrograde motion against the stars of western Aquarius. Three days later, on Thursday the 6th, Pluto is in opposition to the Sun as it moves westerly against the stars of southern Ophiuchus.

As the handle Big Dipper goes over the northern pole around 9 PM Daylight Time, Crux, the Southern Cross, goes over the southern pole. Too far south to be seen from most northern climes, the Cross is an icon of the southern skies. From latitudes south of roughly that of the Tropic of Cancer (23.5 degrees north), the Southern Cross makes a near-magical appearance, followed by two bright first magnitude stars, Rigil Kentaurus (Alpha Centauri) and Hadar (Beta Centauri), a sight that when first seen by northerners is never forgotten.

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