Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Cassiopeia, her Chair upside down, rises at right
through the shutter of the 4-meter telescope at Kitt Peak, the
telescope itself silhouetted against the sky at left. Peaking
through openings in the telescope tube at left are Delta, Zeta, and Mu Cephei (Herschel's Garnet Star).
Astronomy news for the week starting Friday, September 3, 2004.
As August passes to September, we sense the scent of fall in the
air, at least in the northern hemisphere: in the southern, they
have the greening of spring. As summer fades, so does the Moon,
which wanes through its last quarter on
Monday, September 6, and thereafter enters the waning crescent
phase and descends toward the dawn horizon. Less than two days
after the quarter, the Moon passes
apogee, where it is farthest from the Earth in its current
round.
Oddly, though the first and third quarters have the same angular
dimensions in the sky, the third is only about half as bright as
the first as a result of a greater proportion of dark volcanic
plains, or " maria," most of which partially fill large impact
basins and are easily visible to the naked eye to make the "Man in
the Moon" and other fanciful figures.
The early morning hours of Thursday the 9th sees the crescent make
a nice triangle with Castor and Pollux in Gemini (the stars to the left), the Moon also topping
Saturn. The following morning, Friday the 10th, is even
better, with the Moon making a neat triangle with Saturn (above and
to the right of the Moon) and brilliant Venus (down and to the right). That same morning, Mercury makes a very close pass to Regulus in Leo, the little planet only a fraction of a degree from
the star, the pair making a difficult sight since they will be so
close to the dawn horizon. Even if Regulus is not noted in morning
twilight, Mercury should be nicely visible as it passes its
greatest western elongation to the Sun on Thursday the 9th. Look
just to the north of east as the sky brightens. Brighter than
anything in the sky other than the Sun and Moon (and the occasional
meteor), Venus still rises early, lofting itself above the eastern
horizon around 3 AM Daylight Time.
As we enter September's evenings, the Big Dipper (the brightest portion of Ursa Major, the Greater Bear) and Cassiopeia (the celestial Queen) stand
opposite each other across from the core of the sky, the North Celestial Pole (the Dipper to the
northwest, Cassiopeia to the northeast), which is marked by Polaris at the end of the Little
Dipper (the brightest portion of Ursa
Minor, the Smaller Bear). Standing on its handle, the Little
Dipper is at its best, though most of its stars are faint and
require a dark sky to see. In between the Dippers, but much higher
than Polaris shine the two eyes of Draco, the Dragon, and nearly overhead is bright Vega of Lyra. Grazing the northern horizon for those who live
north of 45 degrees north latitude is Capella, which will shine high for
us next winter, while far to the south is another Dipper, the
Little Milk Dipper of Sagittarius,
whose handle sticks into the broad heart of the Milky Way.
