Second Sight

Natural History, Feb, 1999 by Joe Rao

Readers may recall the spectacular pairing off last April of Venus and Jupiter, the two brightest planets. Of course, the two did not physically converge; the planets were in what astronomers call a conjunction--the close alignment of two or more astronomical bodies. The planets that can be seen without optical aid--Venus, Mars, Jupiter, Saturn, Mercury, and sometimes Uranus--seem to converge from time to time as they pass one another by. For Venus and Jupiter, this occurs eight to twelve times a decade. Less frequently, three or four of the planets do so.

Some people missed last April's conjunction because of cloud-filled skies--although more probably missed it because it occurred at dawn. Now they will get a chance to observe Venus and Jupiter creeping close to each other again. At the beginning of February, Venus will be prominent in the western sky at dusk. On February 1 it will set two hours after sunset and then progressively later each evening until the 28th, when it sets two and a half hours after sunset. At the beginning of the month, Jupiter will appear 22 [degrees] above and to the left of Venus. With each passing night, Jupiter's separation from Venus will decrease by 1 [degrees] because of the latter's more rapid eastward motion. On the evening of the 17th, the crescent Moon will join the duo, hovering just below Venus. Twenty-four hours later, the Moon will have moved off to Jupiter's left.

On February 23, Venus and Jupiter will appear almost to merge. As darkness falls in the eastern United States, they will be separated by just twelve arc minutes. (Sixty arc minutes equal one degree; one degree equals the average apparent diameter of two full Moons.) Three hours later, when the sky darkens in the western United States, their separation will have widened to seventeen arc minutes. The two will then part ways--Venus going to the east, Jupiter to the west and lower in the sky. They will not appear so close together again until 2083.

Joe Rao is a lecturer at the American Museum--Hayden Planetarium.

The Sky in February

Mercury is in its best viewing position of the year, dangling just below Venus and Jupiter during the third week of February. By month's end, it stands roughly 10 [degrees] above the western horizon about forty-five minutes after sunset. We see Mercury briefly during this month when the fast-moving planet shoots out of the Sun's glare. It sinks back into the Sun's glare in March.

Mars appears as a steadily glowing, yellow-orange "star." It rises in the east-southeast at about 11:45 P.M. at the beginning of February and an hour earlier by the close of the month. Late on the night of February 6-7, the gibbous Moon rises, with Mars positioned just off to its right.

Saturn is a moderately bright, yellowish white object high in the western sky after sunset. It sets at 11:30 P.M. at the beginning of February and at 9:45 P.M. by the end. On the evening of the 20th, it can be seen well to the right of the crescent Moon.

Pluto is again the outermost planet of the solar system, moving beyond Neptune's orbit on the 11th between 11:00 A.M. and noon. Pluto's elliptical orbit at times brings it closer than Neptune to the Sun.

The Moon reaches last quarter on the 8th at 6:58 A.M. New Moon occurs on the 16th at 1:39 A.M., and first quarter on the 22d at 9:43 P.M. On the evening of February 1, the first-magnitude star Regulus, in Leo, is just above an almost-full Moon. From some parts of the eastern United States, the star will seem to be hidden behind the rising Moon, popping into view at about 7:00 P.M. For the first time since 1980, there is no full Moon in February.

All times above are given in eastern standard time.