Skylights featured four times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. The view from an aircraft window
shows the lower half of the 22-degree halo around the Sun caused by
refraction of sunlight through ice crystals. Below it is a bright
"subsun" created by reflection from those same crystals. A faint
arc tangential to the bottom of the halo produced by spinning
pencil-shaped crystals connects the two. (This image appeard on
the
Earth Science Picture of the Day for March 4, 2003.)
Astronomy news for the ten day period starting Friday, March
21, 2003.
The next Skylights will appear on Monday, March 31. The Moon moves
through its last
quarter this week the night of Monday, March 24, rather well
before Moonrise in North America. The morning of Tuesday, March
25, it appears to the southwest of Mars (now
in Sagittarius), the following
morning to the southeast. Then on the morning of
Saturday, the 29th, the Moon will make a beautiful pairing with
bright
Venus, which will lie up and to the left of the lunar crescent.
The week is host to several invisible (or close to invisible)
events. On Friday the 21st, Mercury goes into superior conjunction with the Sun, where it is on the other
side of the Sun from us, and -- if you could see it -- in its full
phase. Two days later, Pluto is
"stationary" against the background stars of Ophiuchus (well off the ecliptic),
and begins its small retrograde motion. Then on Wednesday the
26th, Vesta,
the third largest asteroid (500 km, 310 miles, in diameter) comes
into opposition to the Sun in the constellation Virgo. Though not the largest
asteroid (one of the broken bodies between Mars and Jupiter), Vesta
is the brightest because of its high reflectivity, and is actually
visible to the naked eye, the only asteroid that is. On Thursday,
the 27th, the Moon passes well to the south of
Neptune, and then on the morning of Friday the 28th, Venus
makes an extraordinarily close pass to Uranus
, only 3 minutes of arc to the north. Twilight, however, will
render this event very difficult to see. Such events conclude with
the Moon passing south of Uranus on the morning of Saturday the
29th (about the same time it passes Venus).
While Venus is dropping lower in the southeastern dawn sky, rising
just after the onset of twilight, the big planets still dominate
the evening. Saturn
, in Taurus, is to the west
of the meridian (to the south) at the end of twilight, while Jupi
ter crosses to the south in Cancer around 8:30 PM. Look for the Beehive cluster just to the
northwest of it.
March is the traditional time for the evening rising of Leo, which, more than any other
constellation, marks the beginning of northern hemisphere Spring.
Due north of it lies the very obscure constellation Leo Minor, the Smaller Lion, a modern
artifact of the sky. To the northwest of Leo, above Cancer and Gemini, lies another that is just
as obscure, Lynx -- not
surprisingly, a Lynx (the original name "Lynx sive Tigris," the
"Lynx or Tiger." Lynx marks the space between Ursa Major and Auriga. Some of it was considered by the Greeks to be
an "amorphous" region of Ursa Major. Thirty-eight such "modern"
constellations dot the sky, many in the deep southern hemisphere
that the ancients could not see. If Lynx is too faint to see, at
least admire Leo with its bright star Regulus.
