Astronomy news for the week starting Friday, July 5, 2013.
We begin the week with the Moon in its waning crescent phase as it heads towards
new Moon the night of Sunday, July 7. Your last glimpse of it will
be as an ultrathin crescent in the eastern dawn sky the morning of
Saturday the 6th. With binoculars you might spot Mars up and to
the left of the crescent and brighter Jupiter down and
to the left. We then switch around to see the waxing crescent in the west beginning in
twilight the evening of Wednesday the 10th, with bright Venus up and to
the right of it. By the next evening the growing crescent will be
well to the left of the planet at about the same angle above the
horizon.
We also begin the week, the fifth of July, with the Earth at its
orbital aphelion, where it is farthest from the Sun, 1.7 percent
farther than average. Just a day later, on Saturday, July 6, the
Moon passes its apogee, where it
is farthest from Earth, some 5.5 percent farther than average. The
effect is to diminish the range of coastal tides (which are maximized each month at new
and full Moons when the Earth, Moon, and
Sun are
aligned) to about 25 percent below the average.
While Venus is slowly entering the scene (though still difficult to
see), Mercury
is gone, as the planet passes through inferior conjunction with the
Sun (on the near side of it) on Tuesday the 9th. With four of the
ancient planets either in twilight or gone altogether, we are left
with lonely Saturn. Well
into southwestern skies by the time darkness descends and still a
dozen degrees or so east of Spica
in Virgo (making for quick
identification), even this planet does not hold on for long. After
setting around 1:30 AM Daylight Time, the sky is oddly devoid of
bright ancient planets for well over two hours until Mars and
Jupiter rather invisibly ascend in dawn's light. Since last
February, Saturn has been in
retrograde motion, creeping slowly westerly against the
background stars, approaching Spica. On Tuesday the 9th, the
ringed planet stops retrograding and resumes its normal easterly
motion as it heads back toward Libra, leaving Spica even further behind to the
west.
By midnight, two of the most prominent constellations are split by the
southern meridian, Sagittarius to the left, Scorpius to the right, the Milky Way cascading down through them.
Directly above Scorpius, find the giant pentagon that makes Ophiuchus, with Serpens wrapped
around him, and farther north still Hercules, which lies to the west of the bright star Vega of Lyra.
