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Natural History, May, 1999 by Joe Rao

Mercury can be seen, although with difficulty, at the very beginning of the month, when it arrives at a close conjunction with Jupiter. The planets are less than 2 [degrees] from' each other on the mornings of the 1st and 2d as they rise out of the east-northeast at about 5:00 A.M. Thereafter, Mercury slips deep into the morning twilight and is practically invisible for the remainder of the month.

Venus will actually continue to brighten during June, but the blazing evening star reaches its highest point in the western sky during the latter part of May, not setting until 11:45 P.M. As it approaches its greatest elongation, the planet's overall image in a telescope appears to be getting bigger while its phase diminishes. The crescent Moon passes by Venus during the evenings of the 17th and 18th, and on May 30 Venus appears a little more than 4 [degrees] degrees from Pollux, the brightest star in Gemini.

Mars is still brilliant but starts to fade as it recedes farther from Earth after the 1st. On that date, it is the closest to Earth (53.7 million miles) that it has been since November 1988 (see "Celestial Events" April 1999). You'll easily find it in the southeast at dusk, where it shines with a distinct yellow-orange luster, making it a formidable sight. Mars passes close to the constellation Virgo's brightest star (the bluish white Spica) toward month's end, appearing some seven times brighter than the star. A waxing gibbous Moon will be sliding to the north of Mars during the night of May 25.

Jupiter, in the constellation Pisces, gradually emerges from the eastern dawn twilight during May. It lies close to Mercury at the beginning of the month, and by month's end it rises at about 3:00 A.M. On May 13 the crescent Moon hangs below Jupiter.

Saturn will slowly become visible during the second half of May as it gradually frees itself from the bright morning twilight. By the end of the month, look for it as a moderately conspicuous, yellowish white "star" rising out of the east-northeast around 4 A.M.

The Moon is at last quarter on May 8 at 1:28 P.M.; new Moon is on May 15 at 8:05 A.M.; first quarter comes on May 22 at 1:34 A.M.; and full Moon is May 30 at 2:40 A.M. The Moon will be at perigee (closest to Earth) on May 15 at 11 A.M., a distance of 222,000 miles. Because this occurs less than three hours after the new Moon, look for unusually high and low tides for a few days before and after this date. Finally, the Moon will appear to occult (hide) the bright star Regulus, in Leo, during the evening hours of May 21. This phenomenon will be visible across much of North America, except over parts of the southwestern United States. The star will disappear behind the dark, unlit portion of the lunar disk and will reappear about an hour later from behind the bright limb.

All times given am in eastern daylight time.