Skylights featured four times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Jupiter lies just southeast of
the Beehive Cluster in Cancer
and almost within the four-star box that makes Cancer's "Manger" in
this photo taken on March 6, 2003. Castor and Pollux in Gemini lie off to the right. Compare with the "Stars" picture taken 12 years ago,
the pair showing Jupiter having made a full orbit around the Sun.
Astronomy news for the week starting Friday, March 14, 2003.
Skylights is presented a day early this week. We begin the week
with the Moon in its waxing gibbous phase heading toward full, the phase reached the morning
of Tuesday, March 18, about the time of moonset in North America,
which will correspond almost exactly with the moment of sunrise.
The night of Monday the 17th the Moon will be just short of full,
and will rise just before sunset. About one day past full, the
Moon will pass its perigee
point, where it is closest to the Earth, a distance of 363,300
kilometers (225,700 miles), 5.5% closer than average.
The big event for the week is the passage of the Sun across the vernal equinox in Pisces on Thursday, March 20,
marking the beginning of spring in the northern hemisphere, fall in
the southern. At 7:00 PM CST, around the time of sunset (depending
on longitude), the Sun
crosses the celestial equator heading north. It will then shine
directly overhead at the Earth's equator, rise at the North
Pole, and set at the South
Pole. Everywhere on Earth but at the poles, the Sun will rise
due east, set due west, be up for 12 hours and down for 12: hence
the term "equinox." (Technically only: in reality, the half-degree
diameter of the Sun and refraction in the Earth's atmosphere will
cause the Sun to be up for a few minutes more than 12 hours, to
rise at the North Pole a couple days in advance of equinox
passage, and to linger a bit at the South Pole before it finally
gives it up.) Since the Moon passes its full phase just three days
before, it will be just shy of the autumnal equinox in Virgo, causing it to rise close to
exactly east, set west, and be up for 12 hours, creating a lovely,
though accidental, symmetry between Moon and Sun.
In the evening, Saturn and
Jupiter slip slowly westerly when viewed at the
same time of night, the ringed planet now setting around 1 AM,
Jupiter lingering in the western sky until just before dawn. At
the same time, Saturn is moving easterly against the background
stars of western Taurus (just
northwest of Zeta Tauri), while
Jupiter still moves retrograde (westerly) in central Cancer. As Jupiter sets, Venus rises, this brightest of all planets now notably
lower in the brightening southeastern sky. Mars, now in Sagittarius
and near the most southerly point of its celestial journey, is well
to the west of Venus, rising around 2:30 AM.
Jupiter is now just to the southeast of the Beehive Cluster in Cancer,
allowing easy identification of both the cluster and of this dim
zodiacal figure as well (The Beehive is a very pretty sight in
binoculars, which will also enable you to see Jupiter's four large
Moons, Io, Europa,
Ganymede, and Callisto). Note the box of four stars that
surround the cluster, which make an asterism called "the Manger."
To the west shine the bright stars of Gemini, to the east the
lordly figure of Leo, the Lion.
