Skylights featured four times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. The rising Sun announces a
glorious new day.
Astronomy news for the week starting Friday, June 6, 2003.
Due to unforseen circumstances, Skylights is late this week. It
will return on time next Friday. The Moon passes through its first
quarter early in Skylights' week, on the afternoon of Saturday,
June 7, about the time of Moonrise in North America. The rest
of the week it waxes in its gibbous phase,
finally reaching full on Saturday the 14th. Two days before, on
Thursday the 12th, our companion passes perigee,
where it is closest to the Earth on its elliptical orbit, some 5.5
percent closer than its average distance of 384,400 kilometers
(238,900 miles), 30 times the diameter of the Earth. The night of
Monday, June 9, finds the Moon just to the northwest of the star Spica in Virgo.
Saturn has now
passed the point of no return, and is invisible in the evening
skies. Jupiter, however, remains on guard, and is still well
up in the west at the end of twilight. The giant planet then sets
right at midnight Daylight Time, about 45 minutes before Mars
rises in the southeast, the red planet near the Capricornus-Aquarius border.
Two dimmer planets then hold forth, as
Uranus, now well into Aquarius, begins its retrograde motion
(on Saturday the 7th), and Pluto,
well north of the ecliptic in Ophiuchus, is at opposition to the Sun (on Monday the
9th) and best for viewing, not that anyone can see Pluto without a
fairly decent telescope. Pluto has the greatest inclination to the
ecliptic -- 17 degrees -- of any "planet" in the Solar System, and
also has the most eccentric orbit, that takes it from inside Neptune
's, near 30 Astronomical Units, to near 50. Oddly, the planet,
which passed its closest point to the Sun a few years ago, and is
now moving farther away, is now also heating up a bit -- not that
that means much, since its surface is only a few tens of degrees
Celsius above absolute zero.
As the Earth orbits the Sun, the stars and constellations appear in
the evening according to the season. The exceptions are the stars
that immediately surround the pole around which the sky seems to
daily turn. Such circumpolar stars are always visible, neither
rising nor setting. Among the best of these for the northern
observer are the stars of Ursa
Minor, the Smaller Bear, made mostly of the asterism of the
Little Dipper, which has Polaris at the end of its handle. Still,
even the Little Dipper is a bit seasonal. At this time of year,
with the Big Dipper high in the
sky at evening twilight, the Little Dipper is standing more or less
upward, giving us a fine view. Except for Polaris, however, and the two front
bowl stars (Kochab and Pherkad), the constellation's stars
are faint, and require a dark sky to see, the opposite of the
bright stars of the Big Dipper.
