The
Moon grows through its waxing gibbous phase the early part of
the week, reaching full the night of Tuesday the 23rd after
midnight in the Americas. The full
Moon will therefore rise shortly before sunset that night and
set just after sunrise. On Wednesday, the 24th, it passes south of
Neptune in Capricornus. Last
month's full Moon was the lowest of the year for those in northern
latitudes, and this one will be almost as low, especially since the
tilt of the lunar orbit brings it rather well below the ecliptic
plane.
Summer full moons -- this one the Thunder Moon or Hay Moon -- often
take on a beautiful coppery color. When the Sun or Moon are low
above the horizon, you look through vastly more air then when these
bodies are high in the sky. The air absorbs the blue component of
sunlight and turns the Sun or Moon reddish, the effect greatly
enhanced by high summer humidity.
The Sun "captures" a
trio of planetary bodies this week. Jupiter,
completely out of sight, passes conjunction with the Sun on Friday
the 19th, of course far to the other side, about as far from us as
it can get, some 6 1/4 Astronomical Units (the AU the distance
between the Earth and the Sun). Almost exactly a day later, Mercury passes
superior conjunction with the Sun. Mercury and Venus both go
through two conjunctions, one when they are between us and the Sun
("inferior"), and again when they are on the other side
("superior"). Two days after Mercury's passage, Vesta,
the brightest of asteroids, passes its solar conjunction as well.
With all these disappearances, about all you can watch for is
magnificent
Venus, which rides high in the twilight evening western sky and
is quite impossible to miss. About a month from now, the planet
will pass its greatest angle from the Sun, when (because we then
look at half the daylight and half the nighttime side) it will
appear to us like a half moon. It is very close to that
now.
Though the heat of summer is upon us, the late springtime stars
still dominate the very early evening. Look for bright orange Arcturus, the luminary of Bootes, the Herdsman, now falling
into
the evening western sky. Most of the constellation appears as a
large "kite" to the north of Arcturus, only two stars of the
classic figure, Eta (Muphrid) and
Zeta Bootis, splayed out to the south. As Arcturus sinks, white Vega and Deneb rise in the northeast, making
the
color contrast between them and Arcturus rather obvious, the
"redder" color of Arcturus coming from a cooler gaseous surface.
