Skylights featured three times on Earth Science
Picture of the Day: 1
Photo of the Week.. A horizontal arc passes from the
Sun through a bright sundog caused by refraction of sunlight
through ice crystal clouds.
Astronomy news for the week starting Friday, February 6, 2004.
This is a week for the fading Moon. Having passed full the morning
of Friday the 6th, the just-barely-waning gibbous will rise
the night of the 6th just past sunset, and then will rise a bit
over an hour later each night as it approaches its third
quarter on the morning of Friday the 13th. To the south of the
equator, the last quarter will not rise until after midnight.
The night of Saturday the 7th finds the Moon just to the northwest
, which provides a fine chance to watch the lunar motion.
Moving by its own angular diameter in about an hour, the Moon will
approach Jupiter during the night and be almost directly north of
it by dawn on Sunday the 8th. That evening will find the lunar
disk to the other side of the giant planet. All this action
seemingly takes place on the fiction of the "celestial sphere," the apparent globe over our heads.
In reality, the Moon is a mere quarter million miles (almost
400,000 kilometers) away, whereas Jupiter (which now rises around
7:30 PM to the south of eastern Leo) is 1800 times more distant.
Not quite two hours after Jupiter rises, Saturn, high in Gemini, crosses the meridian to the south. To the
southwest in the early evening lies
Mars at the eastern edge of Pisces. Further over, in southwestern twilight, find
that gem of the skies, brilliant Venus. While the other planets set earlier
each night, Venus, as it approaches the
Earth, does the reverse, setting later, now not dropping from
sight until almost 9 PM.
Among the most admired of constellations is Taurus, the ancient Bull. High to the south in early
evening, it lies between Aries
and Gemini, the latter the most
northerly of the zodiacal constellations. Taurus is unique in
having the two most prominent clusters of stars in the sky. The
head of the Bull is made of the nearby (150 light years) vee-shaped
Hyades. While Aldebaran, Taurus's brightest
star, appears to be within the cluster, it is actually just in the
line of sight, somewhat less than half the Hyades' distance away.
To the northwest of the Hyades is one of the most famed of all
groups, the beloved Pleiades,
or Seven Sisters (though only six are commonly seen with the naked
eye), which lies almost three times farther away than the Hyades
(and thereby spans a much smaller angle on the sky). Not only
closer, the Hyades stars are also much older, over half a billion
years of age as opposed to 130 million years for the Pleiades (the
age determined by the kinds of stars still present). As a result
of its relative youth, the Pleiades is filled with bright, massive,
blue stars that give it much of its wintery sparkle.