Astronomy news for the week starting Friday, January 26, 2001.
The Moon spends most of the week in its waxing crescent phase,
finally reaching first quarter on Thursday, February 1 a few hours
before its mid-day rise. The night of Saturday the 27th, the lunar
crescent will be seen a few degrees below brilliant Venus, which in
the Moon's absence continues to dominate the early evening sky.
Venus passed its greatest eastern elongation from the Sun over a
week ago, though little change can yet be seen. Now it is
Mercury's turn, greatest eastern elongation taking place on Sunday
the 28th, making this week a good time to find the two "inferior
planets," those closer to the Sun than we are, stretched out from
the Sun at maximum advantage. Find a clear horizon and look to the
west southwest in dusk to find Mercury, the little planet quite
bright but washed out by the thick air near the horizon and by
fading twilight. Because the sky looks so much like a bowl above
our heads, it is difficult to appreciate the effect of the Earth's
atmosphere. When we look right on the horizon we actually see
through 38 times more air than when we look directly overhead. As
a result, stars and planets appear much fainter as they rise and
set than when they are high in the sky.
Thickness of atmosphere is no deterrent to Jupiter and Saturn,
however, which are now high to the southeast at the end of
twilight, the two planets brilliant near the Pleiades of Taurus,
leading the eye to appreciate the beauty of the Seven Sisters star
cluster. Jupiter is the brighter of the pair, and after Venus (and
of course the Moon) the brightest body of the current sky. Saturn
is just a bit to the west of it. Both bodies are now in normal
direct motion, Jupiter ever-so-slowly pulling to the east of the
About the time Jupiter and Saturn set, around 2 AM, Mars rises.
Now smack in the middle of the classical figure of Libra, the red
planet is being overtaken only slowly by the Earth, and will remain
a morning planet until the beginning of April, when it will finally
begin to rise before midnight.
From mid-northern latitudes, Auriga shines high in the sky above
Orion, Perseus beginning to descend to the northwest. However,
from Auriga to the North Celestial Pole, closely marked by Polaris,
the sky is drab indeed. This area is filled with one of the larger
constellations, and certainly one of the dimmer, the obscure modern
figure Camelopardalis, the Giraffe, its three brightest stars,
which are strung out in a line toward the pole, shining only at
fourth to fifth magnitude.