The Moon
wanes through its gibbous phase during most of the week, and
reaches its third and
last quarter for this cycle on the morning of Thursday, August
1, the Moon then seen high to the south at daybreak. The day
before, our lunar companion goes through its apogee, where it is
farthest from the Earth along its orbital path. The combination of the phase, apogee,
and near-aphelion for the Earth will produce especially weak tides
at the coasts, as the solar tide fills in the lunar at the
quarters, and tides are very sensitive to the distances of the
tide-producing bodies.
Venus
and Saturn
bookend the night, while the outer planets bookend the week. As
the evening sky darkens, Venus shines brilliantly in the west,
and as morning twilight begins to light the sky, Saturn shines
softly in the east, still among the stars of Taurus well to the east of Aldebaran and the Hyades. Jupiter
is following along, and will join the dark pre-dawn skies before
long. On the morning of Friday, July 26th, the Moon will pass a
few degrees to the south of Uranus, which
hovers near the Capricornus-Aquarius border, while Neptune -- deep
in Capricornus -- reaches opposition to the Sun on Thursday, August
1. The giant outer planets have been oddly paired for some time
now, Jupiter and Saturn still close to each other, the closer one,
Jupiter, pulling away from Saturn. Uranus and Neptune are doing
the same thing, but at a glacial pace, Uranus creeping away from
its outer near-twin.
With August comes the height of the summer constellations and the
glory of the Milky
Way. Begin with the two great birds of the northern sky, Cygnus, the Swan, which flies high
above at midnight, and to the south of Cygnus, Aquila the Eagle. Each contains
one of the stars of the Summer
Triangle, Deneb of Cygnus, Altair of Aquila. The third, Vega of Lyra, glows brilliantly to the west of Deneb. The
Milky Way pours down through Cygnus, where the Great
Rift breaks it in two, the rift not an absence of stars but a
vast complex of interstellar dust clouds. The brighter eastern
branch cascades through Aquila and then down through the modern
constellation Scutum and into Sagittarius, where the river of stars
thickens around the nucleus of the Galaxy. Over 25,000 light years
away and buried deeply behind dust clouds, the Galactic
Center is believed to be a massive black hole containing over
two million times the mass of the Sun.
