Photo of the Week. Above all the beauty of the shore
is the blue sky.
Astronomy news for the three weeks starting Friday, July 1,
2011.
Yes, three weeks: it's summertime. We make up for it by presenting
a remarkable triple (no, wait, quadruple) star as the "Star of the
Week." Skylights will resume its normal weekly schedule on July
22, 2011.
We start our triple week with the Moon right at its new phase, at which time it will
eclipse the Sun. But don't
get too excited, as it's again just partial and visible only from
the South Pacific Ocean and a tiny piece of Antarctica. But it's
the third eclipse in a month, June 1 (solar), June 15 (lunar), and
now July 1, showing that if conditions are right for one, they are
for another.
Following that event, such as it is, the Moon then waxes through
its crescent phase until it reaches first quarter about the time of Moonset the
night of Thursday, July 7. We then see a waxing gibbous that grows to full phase the evening of Thursday th 14th.
Seen at near-perfection around midnight, the "Thunder Moon" will be
in between the classical figures of Sagittarius and Capricornus. The remainder of our period sees the Moon
gibbously waning, but not reaching third quarter until Friday the 22nd. We also
note the Moon running the gamut of distance from Earth as it moves
from perigee
(closest to us) on Thursday the 7th to apogee (farthest) on
Thursday the 21st, though the effect is not noticeable to the
eye.
Many are the planetary passages. The evening following that of
new, Saturday, July 2, finds the ultrathin crescent almost directly
beneath Mercury in
bright western twilight, while the following evening will be better
with the Moon off to the left of the little planet, allowing you to
find it easily, at least given a good flat horizon. Then we can
celebrate the Fourth of July by admiring the crescent below Regulus in Leo. The next visit is with Saturn, the growing crescent
well down and to the right of the planet the evening of Wednesday
the 6th, down and to the left of it the following night, and then
to the left of Spica the night of
Friday the 8th, Saturn, the star, and the Moon all in a nice line.
Note the star Porrima just to the
west of the planet. Neptune and then
Uranus get
passed the nights of Sunday the 17th and Wednesday the 20th, these
events however hardly worth the notice. The latter planet, though,
does get a bit of its own notice by beginning
retrograde motion the night of Sunday the 9th.
But it's really Neptune's time for glory, as on Tuesday the 12th,
it will have gone around once in orbit since its discovery in 1846.
Saturn has now become strictly an evening object, as during our
period the setting time goes from local midnight (1 AM daylight) to
11:30 PM Daylight. As noted above, Mercury also makes a decent
appearance, going through greatest eastern elongation relative to
the Sun on the night of Tuesday the 19th. The morning sky, though,
contains much brighter
Jupiter, which, rising about half an hour after Saturn sets,
makes its own transition to local evening (rising before 1 AM
Daylight) while pulling away from Mars, which does
not pop up until roughly just after 3 AM. It passes five degrees
north of similarly-colored Aldebaran in Taurus the morning of Wednesday the
6th. Venus, rising
in bright twilight, is essentially gone.
That leaves Earth, which
adds to the Fourth of July celebration by going through aphelion,
when and where it is farthest from the Sun, a distance of 94.512
million miles (152.102 million kilometers), just 1.7 percent
greater than average. Obviously, given summer's heat, solar
distance has little to do with the seasons, which are caused by the
23.4 degree tilt of the Earth's rotation axis against the orbital
perpendicular.
The middle of our three-week evening action sees the Big Dipper beginning to slip off to
the west. Above the southern horizon look for the dramatic figure
of Scorpius with bright Antares to cross the meridian around 10:30 PM. Up and to the
right of it are two modest stars, Zubenelgenubi (the southern one) and
Zubeneschamali. Though well
within Libra (the Scales), they
also represent the Scorpion's outstretched claws.
