Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. In March of 2004, Saturn (the
bright body to the right) was seen beautifully placed in southern
Gemini. Castor and Pollux lie to the left.
Astronomy news for the week starting Friday, April 2, 2004.
This is the week of the full
Moon, the phase reached on Monday, April 5, close to the time
of moonset (and sunrise) in North America. In homage to spring,
which is now well upon us, the April full Moon is poetically called
the "Grass Moon," and sometimes the "Egg Moon" or "Planter's Moon."
Two days later, on Wednesday the 7th, the Moon goes through perigee
, where in its monthly rounds it is closest to the Earth.
Since the Sun is just past the vernal
equinox in Pisces, this full
Moon is also just past the autumnal
equinox in Virgo, and just
south of the celestial equator. The remainder of the week sees our
companion in its waning gibbous phase as it rises over an hour
later each night.
Venus still
dominates the western evening sky. Though now past its greatest
eastern elongation with the Sun, the planet is still setting
progressively later each night, not dropping below the horizon
until 10:30 PM (Standard Time, 11:30 Daylight Time), well after the
end of twilight. Getting closer to Venus, Mars sets only half
an hour later, the red planet passing north of Aldebaran (and the Hyades of Taurus) the night of Tuesday the 6th. Compare the
similar colors of the two. Mars is red because the iron oxides in
its surface "soil" efficiently reflect the red component of
sunlight, while Aldebaran is reddish because -- for a star -- it is
relatively cool. To the east of these two nearby planets shine Saturn, high in
the early evening in Gemini, and
Jupiter. In
southern Leo, Jupiter is transiting
the meridian to the south about 10 PM (Standard Time), before Venus
and Mars set, giving us a grand show of all four bright planets in
the western sky at the same time.
Early Sunday morning, April 4, most clocks in the US and Canada
advance an hour to "Daylight
Time." "Standard
Times" are the local times at "standard meridians" spaced 15
degrees apart beginning at Greenwich. Eastern Standard Time is
local time at 75 degrees west longitude, Central Standard at 90
degrees, and so on. For Daylight Time, we just pretend we are in
the next time zone to the east, Central Daylight Time being the
same as Eastern Standard Time, again and so on. The effect is that
the Sun seems to rise an hour earlier and set an hour later than it
otherwise would.
