SKYLIGHTS
Astronomy news for the week starting Friday, April 2,
1999.
The Moon, having passed full, is in its waning gibbous phase this
week, rising ever later and passing third quarter the night of
Thursday April 8. Since the Sun recently passed the vernal
equinox, this third quarter, three quarters of the way around the
sky from the Sun, will be just past the winter solstice in
Sagittarius. Because it will be so far to the south, it will be
the latest-rising third quarter moon of the year, not coming up
above the horizon until around 1:30 AM standard time (2:30 AM
daylight time) the morning of Friday, April 9. Tonight, the night
of Friday, April 2, the Moon will pass to the north of Mars, making
the red planet easy to find, the closest approach taking place
around 3 AM on the morning Saturday, April 3.
Mars continues brightening as it plies its retrograde path on the
Libra-Virgo border to the east of the star Spica, which it now far
outshines. It will reach maximum brightness toward the end of
April as it passes opposition with the Sun. Rising in the
southeast around 9:30 PM, Mars is now in the sky with its opposite,
Venus, which sets in the northwest an hour later, Saturn now
setting much earlier, at the end of twilight. Mars and Venus will
continue to approach each other, Venus setting later, Mars rising
earlier, until early summer. However, they will not cross apparent
paths to come into conjunction, as Venus will then quickly be
overtaken by the Sun, while Mars will linger in the evening
throughout this year and into the year 2000.
Reddish Mars, and Venus, a pale yellow-white, contrast more than in
color. Venus, covered with a thick carbon dioxide atmosphere 100
times the pressure of Earth's, and sulfuric acid clouds, is
terribly hot, 470 degrees C (870 degrees F). Mars, with a thin
atmosphere only 1/100 Earth's pressure, is cold enough to have
polar caps and "snow" of frozen carbon dioxide (dry ice). Compared
to Venus, however, Mars is inviting, and will almost certainly be
visited by astronauts sometime in the next century.
The constellations of spring are now in full bloom, great Leo of
the zodiac with the bright star Regulus crossing to the south
around 10:30 PM daylight time. High above, nearly overhead is the
most famed of northern figures, the Big Dipper of Ursa Major, the
Great Bear. South of the Dipper try to find a large patch of faint
stars, the lovely sprawling cluster that makes the entire
constellation of Coma Berenices, Berenices Hair, honoring an
ancient Egyptian queen.
