SKYLIGHTS
Astronomy news for the week starting Friday, June 22, 2001.
As busy as the sky was last week, it is quiet this week. The
biggest event seems to be the Moon's passing its first quarter on
the evening of Wednesday the 27th just about the time the sky
darkens in North America. Four days before that, on Saturday the
23rd, during its ascent of the evening sky in the waxing crescent
phase, the Moon passes through perigee, when it is closest to the
Earth.
Two planets, mythological opposites, now rule opposite portions of
the sky. In the morning, Venus, the ancient epitome of love and
beauty shines gloriously, its light a creamy white. This by-far-
brightest of all planets now rises south of the classical figure of
Aries around 3 AM well before twilight begins to brighten the
eastern sky. In the evening, Mars has already risen by sunset. By
late evening, its brilliant orange-red glow dominates the
southeastern sky between the classical zodiacal constellations
Sagittarius and Scorpius. The other ancient planets, those known
from ancient times, Jupiter, Saturn, and Mercury, are out of sight,
though Saturn can be glimpsed in the early dawn.
Venus and Mars are in reality the opposites of their mythological
natures. Venus, for all its planetary beauty, is an inhospitable
place, the bright reflecting clouds made of sulfuric acid that
float in a thick, dense carbon dioxide atmosphere that drives the
surface temperature to 470 degrees C (nearly 900 degrees F), about
the temperature of a self-cleaning oven. Mars, on the other hand,
is for all its cold near-airlessness, a place we could actually
visit, and almost certainly will sometime in the future. The
temperature can reach the freezing mark, and powerful evidence
shows that water once flowed on the planet, though the air (again
carbon dioxide) pressure -- about 1 percent that of Earth's -- no
longer allows it.
As the sky darkens, orange Arcturus shines high to the south,
reddish Antares down and to the left and to the right of Mars.
Compare their colors. Which appears the reddest? We probably all
differ in our assessments. Down and to the right of Arcturus,
Spica shines blue-white, the color contrast between it and the
other three bodies quite noticeable. To the right of Spica is the
box of stars that makes Corvus the Crow, a springtime constellation
now making way for the stars of summer. Farther yet below Spica
are the sprawling stars of northern Centaurus. If you are
reasonably south of about 40 degrees north latitude, you might
glimpse the fuzzy ball of the grandest globular cluster of stars in
the Galaxy, magnificent Omega Centauri.
