Astronomy news for the week starting Friday, February 16, 2001.
Having just passed its last quarter, the Moon spends the entire
week in its waning crescent phase, New Moon not reached until next
Friday, the 23rd. Watch in the morning sky as the Moon both slims
and falls farther each day toward the eastern horizon, first
through Sagittarius and then climbing northward a bit into
Capricornus before it encounters the Sun. Note that in the
northern hemisphere that the illuminated side of the waning
crescent points downward to the left. After the Moon passes new,
the evening waxing crescent will point down and to the right.
Illustrators of ads and of children's books commonly get it
backwards or otherwise wrong. While admiring the waning Moon, be
sure to look for brightening Mars, which will shortly be passing
above its namesake, the bright reddish star Antares ("like Mars,"
"Ares" the Greek version of the god of war) in Scorpius.
However, Venus, not Mars, dominates the week, as the second planet
from the Sun passes greatest brilliancy for its current evening
appearance on the night of Wednesday, February 21. Just look to
the southwest in fading twilight. Venus, always third in
brightness after the Sun and Moon, now reaches magnitude -4.6, 17
times brighter than the sky's brightest star, Sirius, and 8 times
brighter even than Jupiter (which, with Saturn, is high in the sky
to the south in early evening and is now making an easterly trek
through Taurus). When Venus is on the other side of the Sun, at
superior conjunction, we see the full sunlit face. As the planet
swings around the Sun toward the Earth, we see (through the
telescope) progressively more of the nighttime side, and the planet
becomes gibbous, and then at maximum elongation from the Sun it
looks like a quarter Moon. Now past maximum elongation, it is a
thin crescent. However, even though we see relatively less
daylight, the planet is getting closer to Earth, so its angular
size and brightness continue to grow -- until now, after which the
phase effect becomes more important. Think how much brighter Earth
(which would always be near "full") would be from Venus (except of
course you would never see it from the ground because of Venus's
perpetual thick cloud cover).
Of all the bright winter constellations, Auriga, the Charioteer,
seems to get the least respect, perhaps because it is so dominated
by Orion, not in the zodiac like Gemini and Taurus, and for most in
mid-northern latitudes so high that one needs to look nearly
overhead. There you can admire the sixth brightest star in the
sky, Capella (the "she-goat"), and the little three-star triangle
to the southwest of it that makes an asterism (an informal
constellation) called "the Kids." The southernmost star of the
pentagonal figure (Elnath) is held in common with Taurus, and
represents the Bull's northern horn.