Astronomy news for the week starting Friday, July 14, 2000.
The Moon waxes through its gibbous phase early in the week,
reaching its full phase on the night of Monday, the 14th, when it
will rise around sunset, set near sunrise, and be up all night.
With the Sun now just having passed into Leo, this month's full
Moon will be near the Capricornus-Aquarius border. Since Neptune
and Uranus both recently passed opposition with the Sun, the Moon
encounters them both before it reaches full, Neptune on Sunday the
13th, Uranus a day later.
Venus still lies very low and almost out of sight in the
northwestern evening twilight sky, but will gradually make an
appearance as the month wears on. At the same time, Jupiter and
Saturn make an official appearance in the evening sky, both now
rising just before local midnight (1 AM daylight time). Jupiter,
in Taurus and just to the east of Saturn, is unmistakably bright,
second in the sky only to Venus (not counting Mars, which at its
very closest can for a time become brighter than Jupiter). Jupiter
is still slowly pulling away from Saturn, and will keep doing so
until fall and the two enter their retrograde motion (caused by the
Earth swinging between them and the Sun). The two Solar System
giants make a fine sight situated roughly between Taurus's two
clusters, the Hyades (which make Taurus's head) and the Pleiades
(the famed Seven Sisters).
Though the bright Moon blots out the fainter stars, it cannot
defeat the Summer Triangle of first magnitude stars, which consists
of Vega in Lyra (at the western apex), Deneb in Cygnus (at the
eastern), and Altair in Aquila (southern). All are white "class A"
stars, but the similarity ends there. Vega is the hottest and
apparently brightest of the trio, rapidly-rotating Altair the
closest and coolest, and Deneb by far the most distant and
luminous. Deneb, a rare white supergiant star, if placed at Vega's
distance, would be many times brighter than Venus and would cast
easily visible shadows on the ground.
Such large configurations that join constellations are not common
in our constellation lore. The best-known are the Summer Triangle
and the Winter Triangle that joins Orion, Canis Major, and Canis
Minor through Betelgeuse, Sirius, and Procyon. Lesser known is the
Great Diamond that links Leo, Virgo, Bootes, and the modern
constellation Canes Venatici through Denebola, Spica, Arcturus and
Cor Caroli. In the Southern Hemisphere, the False Cross joins Vela
with Carina, making a lesser version of Crux, the famed Southern