Astronomy news for the week starting Friday, July 6, 2001.
The Moon falls "between quarters" this week, spending the entire
seven day period in its waning gibbous phase, full moon having
taken place last Thursday, July 5th, the third quarter not being
passed until next Friday, July 13. As it moves through the
constellations of the Zodiac, it passes south of Neptune on
Saturday the 7th, south of Uranus on Sunday the 8th (both planets
in Capricornus), and its apogee (where it is farthest from the
Earth) on Monday the 9th.
The planets put on quite a show for us this week. In the evening,
Mars, four degrees south of the ecliptic and about as southerly as
it can get, glows a brilliant red just to the east of the bright
reddish star Antares in Scorpius. The planet, brighter than the
brightest star and comparable to Jupiter, lies above the great
curve of stars that make the Scorpion's tail. Since Mars moves in
orbit only a bit slower than Earth, we will have it with us in the
evening for the rest of the year.
The big event, however, takes place the morning of Friday, the 13th
(a lucky day!) when Venus, Saturn, and the bright star Aldebaran of
Taurus all gather together into a tight equilateral triangle below
the Pleiades star cluster (Saturn down and to the left of Venus,
Aldebaran below, to the south of Saturn). Venus is now at its
earliest rising of the year, coming up just before 3 AM daylight
time, about an hour ahead of twilight. As the sky grows light, you
might then glimpse Jupiter and Mercury just above the east-
northeast horizon, Mercury (the fainter) about two degrees down and
to the right of Jupiter. The pair comes into conjunction the day
before, on Thursday the 12th. Three days before, on Monday the
9th, Mercury passes its greatest western elongation, the little
planet 21 degrees to the west of the Sun.
Even the asteroids get into the act, as Ceres, the largest of them
(though only 900 kilometers across and invisible to the naked eye)
passes opposition with the Sun on Saturday, the 7th. Only number
4 in discovery order, 500-kilometer wide Vesta (the third largest
of them), can be seen without optical aid, and then just barely.
Nearly 100,000 of the critters have been discovered. Vast numbers
of tiny ones small enough to hold in your hand hit the Earth every
day as meteorites.
Two crowns ride the nightly sky, one in the north, the other in the
south. As the sky darkens, look 30 or so degrees north of the
equator (nearly overhead for mid-northern latitudes) to find the
gentle curve that makes Corona Borealis, the Northern Crown. If
you are far enough south, around 1 AM you can watch the passage of
Corona Australis, another curve of stars that makes the Southern
Crown, which lies directly below the Little Milk Dipper of