Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. The near-rising Sun illuminates
aircraft contrail clouds, while honoring them with a sunpillar. Sunrise itself intensifies the scene.
Astronomy news for the week starting Friday, March 12, 2004.
The Moon begins our week near its last quarter, the
phase reached on Saturday, March 13, from which it will wane in the
crescent
phase, rising ever later past midnight each night as it
approaches its new phase on Saturday, the 20th. The morning of
Wednesday the 17th it will pass a few degrees south of Neptune,
then during the day on Thursday the 18th about the same angle south
of Uranus.
While the outer planets --
Mars,
Jupiter, and Saturn
-- shift a bit to the west when viewed at the same time each
night, Venus
climbs to the east (relative to the Sun). As twilight ends, Venus
is high in the western sky and does not set until as late as 10 PM.
To the east of Venus, Mars sets about an
hour and a quarter later, the red planet in Taurus to the southwest of the Pleiades. Saturn (in Gemini) is now transiting the
meridian to the south around 7 PM, and is followed by Jupiter
(south of Leo) which now makes its
meridian passage at midnight.
The big event, however, is the beginning of astronomical spring,
which commences about as early as possible because of the leap year
that added an extra day to the calendar last February. The actual
date and time depends on location. The Sun will cross the Vernal Equinox in Pisces at 1:49 AM EST and 12:49 CST
on the morning of Saturday, the 20th, while in the west (at 11:49
and 10:49 PST, successive hours earlier for Alaska and Hawaii) the
event happens on Friday the 19th. At that moment, the Earths's
rotational axis will be perpendicular to the line to the Sun,
rendering the Sun directly overhead at the Earth's equator.
Everywhere on Earth except at the poles, the Sun will rise due
east, set due west, be up for 12 hours and down for 12 hours (hence
"equinox"). Technically, the Sun (or the solar center, ignoring
refraction by the Earth's atmosphere) will rise at the north pole and
set at the south
pole for six months of respective day and night.
From the southern hemisphere, great Argo, the Ship, dominates much of the seasonal sky.
While much of the three-part super-constellation is hidden for mid-
northerners, much of Puppis (the
Ship's Stern) can be seen low to the south beneath the magnificent
figure of Canis Major, as it wraps
to the east and south of Orion's
Greater Dog, which contains Sirius, the brightest star of the
sky. If you are far enough south, below about 35 degrees north
latitude, you might spot Canopus
in Argo's Carina (the Ship's Hull)
almost immediately below Sirius. Just to the north of Sirius,
however, lies one of the dimmer constellations of the sky, the
modern figure of Monoceros, the
Unicorn, which stretches to the east of Orion, much of it within
the Winter Triangle made of Betelgeuse, Procyon (in Canis Minor, the Smaller Dog), and Sirius.
