Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. A deep view of
Cygnus, the Swan,
has bright Deneb near the upper left, Albireo at lower right, and
the Milky Way running between the two.
Astronomy news for the week starting Friday, July 18, 2003.
The Moon
wanes through the last of its gibbous phase the early part of the
week, then passes through its third, or last, quarter the night of
Sunday, July 20, against the stars of Pisces, about the time of Moonrise in North America,
the phase near perfect. About a day later, it passes through
apogee, where it is farthest from Earth. The remainder of the week
sees it waning through crescent as it climbs to the north close to
the ecliptic. The morning of Thursday the 24th, the slimming
crescent will fall between the Pleiades and Hyades
of Taurus, this ancient
constellation of the Zodiac now nicely having cleared the rising Sun
.
Except for Mars, all
the "ancient planets," the ones known from unremembered time, are
out of the way and close to invisible. Jupiter sets in mid-
twilight, as does
Mercury, while rises just as dawn begins, followed by Venus
in mid-morning twilight. The stage thus belongs to the red planet,
which lofts above the southeastern horizon shortly before 11 PM
daylight time. By dawn, it is directly south, dominating the dim
stars of southern Aquarius. Though
the Earth is slowly catching up to it, Mars still moves along to
the east against the starry background. Slowing its pace, the
planet will begin retrograde, or westerly, motion against the stars at the
end of the month, and will then take about another month to reach
ts glorious opposition, when it will be at its closest and
brightest since any time in remembered history.
As the sky darkens, those at mid-northern latitudes see the Big Dipper swinging into the
northwest, while the Little Dipper
stands tall, its two front bowl stars high above Polaris (which nicely marks the
North Celestial Pole) at the end of the handle. Between the two
curl the aptly named stars of Draco, the Dragon, one of which -- Thuban -- was the pole star in
ancient times. To the east of the Dipper, above Hercules, the Dragon's head looks
downward, its eastern side nicely lined up along the "solstitial
colure," the circle around the sky that connects the two solstices
(in Sagittarius and Gemini) and the celestial poles.
Ninety degrees away runs the "equinoctial colure," which does the
same with the equinoxes (in Pisces and Virgo) and the poles. While the North Celestial Pole
has a fine marking star, the South Celestial Pole goes without. At
least it goes without for now, as precession, the 26,000-year
wobble in the Earth's axis (caused by the pull of the lunar and
solar gravity on the Earth's equatorial bulge) will bring Polaris
off the northern pole, and will eventually bring fine pole stars to
the south.
