Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. The "vee" of stars at center
represent the modern asterism "Poniatowski's Bull," which
commemorates Stanislaus Poniatowski, King of Poland from 1764 to
1795. At far right is Rasalhague (Alpha Ophiuchi).
Down and to the right of the "vee," just above Cebalrai (Beta Oph), is the star
cluster IC 4665.
Astronomy news for the week starting Friday, September 17,
2004.
The week's events are compacted in its middle. First up is the
first quarter Moon, the phase passed on Tuesday the 21st
shortly before moonrise in North America. Just a day later, the
Moon passes perigee
, where it is closest to the Earth. Watch in the evening hours
early in the week for the growing
crescent as the Moon passes through northern Scorpius, seen to the right of Antares the evening Sunday the 19th,
to the left the following night. Then later in the week admire the
waxing gibbous
as the Moon heads towards full.
Next up is giant
Jupiter, which on the same day as the Moon passes first quarter
(Tuesday the 21st) passes conjunction with the Sun and moves over into
the morning sky. You'll see it rising out of morning twilight in
mid-October, quickly passing Mars, the latter keeping
better orbital pace with the Earth and thereby taking a long time
to rise into a dark morning sky. While these two planets now
remain out of sight, Venus and
http://saturn.jpl.nasa.gov/home/index.cfm">Saturn shine
gloriously before dawn graces the sky, Saturn slowly pulling away
from much brighter Venus.
Lastly, but most importantly, the Sun passes the autumnal equinox in Virgo to mark the beginning of
northern
fall (and southern-hemisphere spring) at 11:30 AM Central
Daylight Time (12:30 PM EST, 9:30 AM PST, 8:30 AM in Alaska, and
6:30 AM in Hawaii) on Wednesday, the 22nd (early this year because
of leap year). At that time, the Earth's axis will stand
perpendicular to the line to the Sun, the Sun will pass overhead at
the Earth's equator, will technically set at the North Pole, and
rise at the
South Pole. (The half-degree angular size of the Sun and
refraction by our atmosphere will make it linger above the horizon
at the north pole for a couple days, and advance rising at the
south pole.) The Sun will thereafter rise progressively farther to
the south of east, and set farther to the south of west as the days
shorten in the northern hemisphere and the weather chills.
As Scorpius and Antares move off into western twilight, so does one
of the giants of the pantheon of constellations, Ophiuchus, the Serpent Bearer,
which lies directly to the north of Scorpius. So too does the
Serpent itself, Serpens the only
constellation that comes in two separate parts, Serpens Caput (the
"head," to the west of Ophiuchus) and Serpens Cauda (the "tail," to
the east). Directly north of Ophiuchus is Hercules, and yet farther to the north is the head of
Draco, the Dragon, with two
curving paths of stars lying between it and Polaris, which stands nearly
unmoving near the North Celestial
Pole.
