Astronomy news for the week starting Friday, September 13,
2013.
Skylights now resumes its normal weekly schedule. Thanks for your
patience.
Skylights' new week provides the runup to the full Moon. We start on Friday,
September 13, with the Moon barely in its waxing gibbous phase, which lasts until full Moon
the night of Wednesday the 18th, but really the morning of Thursday
the 19th about the time of Moonset in North America, allowing you
to see it in full bloom. And it's a special one too, the classic
Harvest Moon, which is the full Moon nearest the first day of fall,
on which the Sun crosses the celestial
equator at the autumnal
equinox on its way south (this year on Sunday the 22nd). It's
more than just a name. At
this time of year, with the full Moon near the Vernal Equinox, the ecliptic (the path of the Sun,
which the Moon closely follows) in the eastern evening sky lies
rather flat against the horizon. As a result, the delay in
Moonrise from one night to the next around the time of full phase
is quite short, and the early evenings are flooded with Moonlight.
See the effect for yourself as the barely waning gibbous rises just after sunset the
night of Thursday the 19th. During its trek, the Moon does not
encounter much, just Neptune on
Tuesday the 17th and Uranus on Friday the 20th. On Sunday the 15th,
the Moon goes through perigee, where
it is closest to the Earth.
For a long time now,
Venus has been coming up ever higher in western evening
twilight, while Saturn has been heading downward toward it, the two
encroaching on one another's territory. Look the night of Monday
the 16th to see the ringed planet almost directly above brilliant
Venus. The two come into formal conjunction with each other with
Venus four degrees north of Saturn on Thursday the 19th. After
they set (about as twilight ends), we must wait until around local
midnight (1 AM Daylight) for the northeasterly rising of Jupiter in Gemini.
Scuttling along in Cancer to the
southeast of the Beehive
Cluster, Mars is up
shortly before 3:30 AM. In lesser news, on Tuesday the 19th, Pluto stops its
retrograde (westerly) motion against the stars and resumes its
snail-like easterly motion.
Yes, autumn is nigh, and that means the entry of the fall constellations. Later in the evening,
look well to the east of the Summer Triangle of Vega-
Deneb-Altair (which will be straddling the
meridian around 10 PM Daylight) to see
the rising of the Great
Square of Pegasus, the
mythical horse of the hero Perseus, which will be rising in the far
northeast. South of the Square lies the "Circlet" of western
Pisces. To the southwest, see the summer figures of Sagittarius and Scorpius (the latter practically sitting on Ara, the Altar).
