Photo of the Week.. A red sunrise lights the eastern
Astronomy news for the week starting Friday, September 13,
The week begins with the Moon in its first quarter, the phase
reached just about the time of Moonrise in North America.
On the average rising near noon, the first quarter is a fine time
to watch the Moon progress up the eastern sky during the daytime.
With the Sun approaching the autumnal equinox in Virgo, the first quarter will lie
just shy of the winter solstice in
Sagittarius, making it the most
southerly first quarter of the year. As the Moon progresses
through its waxing gibbous phase, it rises progressively later
until, when full phase is reached on Saturday the 21st, it will
rise around sunset. During this waxing stage it will pass beneath
the night of Monday the 16th, and south of Uranus
on Wednesday the 18th.
Though the Sun is getting closer to Venus, the
planet is still in direct, or easterly, motion against the starry
background; the Sun is simply moving faster along the ecliptic and
is catching up with it. Venus is also still increasing in
brightness, though the increase is not obvious as the planet is now
rather low against the western horizon at dusk. Through the
telescope Venus is now presenting itself as a large crescent.
Little Mercury, on
the other hand, enters its backward, or retrograde, motion on
Saturday the 14th, the planet all but invisible against twilight
With the inner planets disappearing into western twilight, the
giants begin to move into the evening. Saturn now
Taurus just before midnight
daylight time. Jupiter,
brightly visible to the east in morning twilight, will enter the
evening sky in late October. Mars has also
cleared the Sun. Rising in bright morning twilight, it is now
about as elusive as Mercury.
As the Sun approaches the equinox, note that it lies due west
shortly before sunset, and due east shortly after sunrise, making
driving east and west in morning or evening rather difficult. At
this time of year, the Sun is trekking quickly
to the south, making the movement of the sunset point along the
horizon quite obvious.
As the sky darkens, the great Summer Triangle is now in full bloom, Vega nearly overhead, Deneb to the northeast, Altair to the south. Near and within
its confines lie two exquisite constellations, Delphinus, the Dolphin (which looks like a small hand
pointing a finger), and Sagitta, the Arrow (which rather looks like what it is
supposed to be), the two bracketing the line between Deneb and
Altair. For a celestial challenge, try to find the modern
constellation of Vulpecula, the
Fox, which lies between Sagitta and Albireo, the star that represents
the head of Cygnus, the Swan (Deneb
making the tail).