Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Star clusters (circled) and
variable stars (yellow labels) in
Taurus surround and outline a
blank area, the Taurus-Auriga
dark cloud, a vast dusty cold
interstellar cloud complex 460 light years away that blocks
background starlight and in which stars are being formed. Here we
also look toward the anticenter of the Milky Way, directly away
from the center in Sagittarius.
Astronomy news for the week starting Friday, March 11, 2005.
Skylights will next appear on March 25 and will then resume its
usual weekly schedule. Thanks for your patience.
The Moon begins the week in a slim waxing crescent phase that will be
just visible low above the western horizon in twilight. Watch as
the crescent fills out, the Moon setting ever later, the nighttime
side glowing with Earthlight, as it approaches then passes
first quarter (Earthlight disappearing) on Thursday, March 17.
Over the remainder of the fortnight, the Moon waxes through its
gibbous phase to full, which will
be reached on Friday the 25th.
The Moon will provide a wonderful way of finding Mercury,
which is now making a fine near-spring appearance. Look in western
evening twilight the night Friday, March 11, for the slim crescent
Moon hanging just above the horizon. Mercury, quite bright, will
be just to the right of it, the pair having been in formal
conjunction earlier in the day. Greatest eastern elongation, when
the little planet is at its greatest extent to the east of the Sun,
takes place the next day, causing it to linger until twilight ends.
For nearly a week around this time, Mercury will make a nice sight
if you look shortly after sunset. Be sure you have a clear
horizon; binoculars will help.
A week later, the fattening gibbous Moon will make a nice pass
through Gemini. Look for Saturn
down and to the left of the Moon the night of Friday the 18th and
down and to the right of it the following evening, the Moon and
Saturn making a lovely quartet with Gemini's bright stars, Pollux and Castor. Saturn now crosses the
meridian to the south just as twilight ends, which is when Jupiter
(in Virgo) rises in the
southeast. The ringed planet ceases its
retrograde (westerly) motion on Monday the 21st, when it
resumes its normal easterly movement against the background stars
(retrograde caused by the Earth swinging between the planet and the
Sun). With Jupiter, Mars
rules the
morning planetary sky, the red planet now rising around 3:30 AM as the Earth
slowly catches up with it.
'Tis the Earth again in the news, really Earth and Sun. At 6:33 AM CST
(7:33 AM EST, 5:33 MST, 4:33 PST) on Sunday, March 20, about
sunrise in mid-America, the Sun crosses the vernal equinox in Pisces, and spring will begin in the northern
hemisphere. At that time, the Earth's axis will be perpendicular
to the direction to the Sun, the Sun will be overhead at the
equator, will rise due east, set due west, and except for the
daylight-extending effects of the Sun's half-degree diameter and
refraction by the Earth's atmosphere (which lofts the Sun half a
degree upward at the horizon), days and nights will be of equal
length. The Sun also technically rises at the north pole, and sets
at the south pole, throwing the south polar
station into ever deepening twilight and finally a 24-hour
night. As the Sun gets higher, its rays become
more concentrated in an area of ground, and the weather warms.
Welcome all to spring.
While the spring stars are coming forth, those of winter linger on.
Look into the west northwest of Orion for Taurus,
which is highlighted by two marvelous clusters, the vee-shaped Hyades that make the head of the
celestial bull, and the Pleiades, the Seven Sisters, said to be pursued by
Orion as he treads the nightly sky. Northeast of Taurus is Auriga. On the border between
Taurus and Auriga is the "anticenter" of the Galaxy, the direction
exactly opposite the Galactic center, which lies behind the great
star clouds of Sagittarius.
