Photo of the Week. Planet Earth. The towering Andes,
raised by a gigantic continental collision, thrust their peaks to
the sky. Glacier National Park, Argentina, Patagonia, photo
courtesy of Lisa Zak, with thanks. See full
resolution.
Astronomy news for the two weeks starting Friday, July 15,
2016.
The next skylights will appear June 29.
As we open up the fortnight, the Moon is in its waxing gibbous phase, heading toward
full the evening of Tuesday, July 19,
when (known as the Thunder or Hay Moon) it will rise just barely
after sunset in North America. The evening of Friday the 15th, the
Moon will lie above Saturn with
Mars to the right and Antares in Scorpius down below, while the following night it will
shine to the left of the ringed planet. After passing third quarter the night of Tuesday the 26th
(before moonrise in North America) the Moon turns into a waning crescent, the phase ending at new
Moon on August 2. The morning of Thursday the 28th, the crescent
will make a fine triangle with the Pleiades up and to the left and the star Aldebaran in Taurus below the famed cluster of
the Seven Sisters. The morning of Friday the 29th, the thinning
crescent Moon will appear tight against the star Aldebaran, and
will actually cross over or occult it as seen from the southern
and eastern US, though for most sites in twilight. The event takes
place at roughly 5 AM CDT, but depends considerably on the exact
location. The Moon passes perigee, where
it is closest to Earth, on Wednesday the 27th, the event not really
sensible to the eye.
As evening falls, Jupiter still
dominates the deep early-evening western sky, though by the end of
our two-week term it will set about at the end of twilight, when
the sky becomes fully dark. So we look to the other planets that
grace the sky, Mars then Saturn as augured above. Only slowly
falling behind the orbiting Earth, Mars sets around 1 AM Daylight
Time, Saturn following roughly an hour later. Now moving to the
east against the background stars, Mars is slowly catching up with
the ringed planet, the two coming into conjunction with each other
on August 25, Mars's motion obvious almost from night to night.
Toward the end of July the Delta Aquarid meteor shower comes to its vague peak,
producing a few meteors per hour while in competition with other
minor showers going on at the same time. Meteor showers are named
after their apparent points of origin, which is a perspective
effect, the meteoroids actually travelling on parallel paths as
they strike Earth's atmosphere.
Saturn is directly above Scorpius, which along with Sagittarius to the east (recognizable
by its upside-down "Little Milk Dipper, both in the heart of the
Milky Way ) are the southernmost
constellations of the Zodiac, the figures that embrace the
apparent path of the Sun. To the west of Scorpius lies Libra, whose two most prominent
stars (Zubelelgenubi and Zubeneschamali) are the Scorpion's
outstretched claws. Farther east, as the sky darkens find bright
Spica, the luminary of sprawling
Virgo, which holds the autumnal equinox, where we find
the Sun
on the first day of Fall.
