Astronomy news for the week starting Friday, July 23, 2010.
The week of the full Moon is upon us, the phase passed the
evening of Sunday the 25th about the time of Moonrise, allowing a
near-perfect full Moon to be seen. The only time a really perfect
full phase is witnessed, however, is during a total eclipse, with the Moon exactly opposite
the Sun. This one passes a bit north of the Earth's shadow. We
then have a couple days of the waxing
gibbous phase before full, followed by a bit more of the waning gibbous to take us out of the week.
There are no fine planetary passages this week, though we will see
the Moon slowly approaching Jupiter. It
does, though, pass apogee, where it
is farthest from Earth, the night of Wednesday, the 28th.
The wonderful string of western evening planets, though enhanced by
Mercury, is slowly fading into the sunset. The little one
(Mercury) lies low in twilight at the right-hand (northern) end of
the parade, while up and to the left of it is obvious Venus
, then farther up Mars
and Saturn
, the red planet slowly catching up with its far more distant
companion, the two anticipating their conjunction on August 1.
But look early and with a good flat horizon, as Mercury sets
quickly in bright twilight, followed by Venus shortly after
twilight comes to a close. Less than half an hour later, Mars and
Saturn go down as well.
At the same time, though, giant and very bright Jupiter rises due
east, around 11 PM Daylight time. Among the fainter stars of western Pisces, to the south of the
Great Square of Pegasus, Jupiter dominates the
late night and morning skies, shining far brighter than any star.
On Friday the 23rd, Jupiter stops its normal easterly motion and
begins to move backwards (
retrograde), the result of the Earth's starting its passage
between Jupiter and the Sun.
The coming month of August is known for its Perseid meteor
shower. But July has one too, though of lesser rank. Mid-July
marks the beginning of the
Delta Aquarids, which stretch across the month and into August,
one portion even into September. With luck and a dark sky you may
catch one or two in the late morning hours.
Oddly, though by coincidence, the three brightest stars -- Sirius (Canis Major), Canopus
(vel-p.html">Carina), and Alpha Centauri (Centaurus) -- are in the southern sky, with only Sirius
readily visible from northern climes. Numbers 4 and 5, and 6,
though -- Arcturus (Bootes), Vega (Lyra), and Capella
(Auriga) -- are in the north.
This is a fine time of year to admire the first two of these,
orange Arcturus in the evening's west beneath the Big Dipper and (just a hair
fainter) white Vega climbing the northeastern sky as Arcturus
descends.
