Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
.
Photo of the Week.. A remarkable "heiligenschein"
("holy glow") surrounds the invisible shadow of an airplane 35,000
feet above the prairie floor. You can see the same thing
surrounding the shadow of your head seen against dewy grass, the
effect caused by the "backscattering" of sunlight. Stretching very
faintly to the left is the shadow of the aircraft contrail.
Astronomy news for the week starting Friday, February 14, 2003.
Happy Valentine's Day to all.
Our Moon brightens during week, cutting out the view of the
faintest stars, as it passes from waxing gibbous through full on
Sunday, February 16, just about the time of Moonrise in North
America, and then into waning gibbous. While the full Moon is only
double the reflecting area of the quarter, it is some eight times
as bright, since the shadows of craters and mountains disappear,
and 180 degree reverse reflection of sunlight is so much more
efficient. With the Sun
now climbing ever higher up the ecliptic, the full Moon is
seen more to the south each month, and this time it finds itself
nestled near the Sickle of Leo.
The night before full, on Saturday the 15th, the near-full-Moon will be
seen just to the east of bright Jupiter.
The giant planets now rule the non-lunar nighttime sky, Saturn
retrograding westerly in eastern Taurus, Jupiter in eastern Cancer, two constellations of the Zodiac to the east.
Saturn's angular speed against the starry background has slowed in
preparation for it going back to direct motion, so Jupiter is
catching up with it a bit, though not by very much. Saturn
transits the meridian high to the south early now, around 7:30 PM,
by which time Jupiter shines high in the east. In the morning sky,
Venus is getting notably closer to the Sun, now rising about an
hour before the onset of dawn. It then brilliantly punctuates the
growing twilight
to the southeast. Look then for Mars
rather well to the west of Venus.
Three other planets make invisible passages of a sort. Uranus, near the Capricornus-Aquarius border, is in
conjunction with the northerly-moving Sun on Monday the 17th, while
on Thursday the 20th, Mercury is in conjunction with Neptune,
both in western Capricornus and to
the west of the Sun.
While Orion stalks the sky high
to the south, the greater glory goes to the heavens' brightest star
Sirius, down and to the left of
the giant hunter. The luminary of Canis Major, the Larger Dog, Sirius twinkles madly in
the cold winter air of the northern hemisphere, the effect caused
by starlight jiggling through patches of warmer and colder
atmosphere on its way to the eye. The star can now be compared
nicely with Jupiter, which shines with a much steadier light.
While the distant stars appear essentially as points to us, planets
present extended telescopic disks. Because the twinkling from one
part of the disk averages out the twinkling from another part, the
effect becomes nearly unnoticeable. To the northeast of Canis
Major barks Canis Minor, the
Smaller Dog, with Procyon as its
first magnitude leader. By 9 PM, Canis Major walks the sky to the
south, allowing a fine glimpse of the bright stars of the great
ship Argo, which sails to the
southeast of the larger celestial dog.
