Photo of the Week. Mars (just below center) passes
through central Taurus in late
August, 2007. Compare the color with Aldebaran down and to the right.
Aldebaran lies in front of the vee-shaped Hyades cluster; the Pleiades shine near the upper right-hand corner.
Astronomy news for the two-week period starting Friday,
September 21, 2007.
Skylights will next appear on October 5, 2007.
The Moon begins our fortnight in the waxing
gibbous phase, passing full on
Wednesday, September 26. It then wanes
through gibbous to its third quarter,
which is reached almost at the end of our period, on Wednesday,
October 3. As it treads its way through the Zodiac, it passes south of Neptune on
Sunday the 23rd and north of Uranus two days
later (both passages quite invisible to the eye). The Moon then
glides 5 degrees north of Mars
during the day (for North America) on Tuesday the 2nd. The night
of October 1st, the Moon will thus shine to the northwest of Mars,
while the following night it will have moved to the northeast of
the red planet.
Two grand events take place on the same day. The first is the
passage of the Sun across the autumnal equinox in Virgo at 4:51 AM Central Daylight Time on Saturday the
23rd, when astronomical
autumn begins in the northern hemisphere. (Add an hour for
eastern time, subtract one for Mountain, two for PDT.) Barring the
effects of atmospheric refraction and the half-degree solar
diameter, the Sun will rise due east,
set due west, be up for 12 hours, and down for 12 hours. It will
then also pass overhead at the Earth's equator, formally set at the
pole, and rise at the south pole.
Thirteen hours later, Venus reaches its greatest brilliancy for this
current morning appearance. Rising now around 3:30 AM and glorious
in the eastern morning sky as twilight begins, the planet is 20
times brighter than the brightest star, Sirius, which gleams in the southeast
well off to the right of Venus. Through the telescope, Venus --
still more or less between us and the Sun -- appears as a large
Rising an hour or so before Venus (less during the latter part of
our period), you can then spot Saturn to the
south of the Sickle of Leo and to
the east of Regulus.
The early evening sky remains graced by
Jupiter. Above Antares, the
giant planet now sets around 10 PM. In between Jupiter and Venus
is Mars, which rises in eastern Taurus about an hour after Jupiter goes down. A
dedicated observer with binoculars might even spot little Mercury in western evening
twilight. The planet reaches greatest eastern elongation on
Saturday the 29th, though with the ecliptic fairly flat against the
horizon, the view will be poor. It passes a mere tenth of a degree
to the north of the star Spica on
Saturday the 22nd.
Some constellations and informal
asterisms just jump out at you. Good examples abound, and include
the Big Dipper, Orion, Taurus, and many others that were known to the
ancients. Others, those invented in more modern times, can be hard
to find, some so much that one wonders what was in the minds of the
inventors. Try for example to locate Telescopium (the Telescope) far south of Sagittarius and Corona Australis. Even harder to find is Microscopium (the Microscope), whose
dim stars sprawl south of Capricornus. A little later in the evening then look
for Sculptor (the Sculptor's
Studio) immediately to the east of Fomalhaut, the bright southern
star that announces the beginning of fall.