Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
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Photo of the Week.. Study in blue and gray. The Sun
has set at 35,000 feet. At bottom is an airplane wing, next up is
the darkening landscape. The dark blue wedge running through the
center is the rising shadow of the Earth, above which is the blue
sky, which still catches sunlight.
Astronomy news for the week starting Friday, June 20, 2003.
The Moon passes its last
quarter this week on Saturday, June 21. Find the quarter high
in the sky to the south in morning twilight, then follow it through
the morning as it sets in the west. The rest of the week finds it
waning through its crescent phase as it heads towards new next
week.
This week belongs more to the Sun, as it passes the
Summer Solstice, the most northerly (and for northern
hemisphere dwellers, the highest) point on the ecliptic (23.4
degrees north of the celestial equator) at 2:10 PM Central Standard
Time on Saturday, June 21 (3:10 PM EST, 12:10 PM PST). At that
moment, the northern end of the Earth's axis will be tilted as much
as possible toward the Sun as astronomical summer begins in the
northern hemisphere, winter in the southern. June 21 is thus the
longest day of the northern hemisphere, the Sun setting as far as
possible to the northwest, rising as much as possible to the
northeast. It will also be overhead at the Tropic of Cancer
at 23.4 degrees north latitude, and will be as high as possible,
23.4 degrees above the horizon, at the North
Pole. From that moment, the Sun will begin its long slide down
toward the Winter Solstice, which it will cross next December. For
awhile, however, the north-south position of the Sun will change
very little, allowing the days to continue to heat through the
summer months. Traditionally, the Summer Solstice is in Gemini. While
precession, the 26,000 year wobble of the Earth's axis, has
technically taken the Solstice past the formal boundaries of the
constellation Taurus, it is
still closer to the classic configuration of the Twins, so we agree
to leave it there.
Planets are disappearing left and right.
Mercury is gone from the morning sky, and while Venus still rises an hour before the Sun, it has become
quite difficult to see. Saturn is now
also gone from the evening sky, and in fact passes conjunction with
the Sun on Tuesday, the 24th, when it crosses into the morning sky.
By the end of July, it will be rising at the start of morning
twilight. That leaves the evening to bright Jupiter, which is lowering in the west, and is now
setting just after 11 PM Daylight Time. Shortly after midnight, Mars rises
in the southeast to take its place.
As the sky darkens, look high to the south to see the lovely semi-
circle formed by Corona Borealis,
the Northern Crown. Draw a line directly south of it, and it
passes through Serpens Caput,
the head of the celestial Serpent, and then down to the three-star
head of Scorpius, the Scorpion,
which lies just up and to the right of bright Antares (Scorpius's first magnitude
luminary). Because of its color, Antares is easy to mistake for
Mars, which (now in Aquarius) is
well to the east of Scorpius and has also well exceeded the star in
brightness.
