Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Even overcast skies can be
beautiful, as attested to by dramatic rolling waves of clouds,
whose appearance depends on direction of
view.
Astronomy news for the week starting Friday, January 2, 2004.
As we start the New Year, best wishes to all for 2004. This
Skylights covers a two-week period. The normal weekly schedule
will resume on Friday, January 16.
The Moon begins the
fortnight in its waxing gibbous
phase, brightening the sky and reaching full on Wednesday, January 7, after
which the
waning gibbous phase takes over until third
quarter passage the night of Wednesday, the 14th, the latter
taking place close to Moonrise in North America.
As it travels through the constellations of the zodiac, the near-
full Moon will take on the giant planets. The night of Tuesday,
the 6th, it will make a nice pass to the north of Saturn, which is now well up in Gemini in the northeast after the
end of twilight. The Moon then repeats the event with Jupiter in
Leo the morning of Monday, the
12th, Jupiter now rising in the east around 10 PM. As the Earth
prepares to pass between Jupiter and the Sun early next March, this
largest of planets begins its
retrograde, westerly (against the stars) motion on Sunday, the
4th.
While Jupiter and Saturn dominate late-night skies, the inner
planets are lords of twilight. You can easily admire
Venus in southwestern skies at dusk, the planet now setting
about an hour after the skies have fully darkened. 2004 is Venus's
year, as it will transit across the Sun next June 8, an event not
seen since 1882. While much more difficult to see, you might watch
for Mercury
low above the eastern horizon in dawn's light as the little planet
approaches its greatest western elongation with the Sun on Saturday
the 17th. In between,
Mars still hangs out to the southwest, setting now around
midnight.
Planets aside, one of the fine features of the fortnight is the
excellent Quadrantid
meteor shower, which peaks the morning of Sunday, the 4th,
originates from a defunct constellation near the Big Dipper, and can produce the
order of 100 meteors per minute.
While the year may belong to Venus, the first week of January
belongs to sister Earth. On Saturday the 4th, at noon central
time, with the Sun
highest in the sky, our planet will pass perihelion with the Sun
(where the two are closest) at a distance of 147.1 million
kilometers (91.4 million miles), 1.7 percent closer than the
average distance of 149.6 million kilometers (93.0 million miles).
That we are closest to the Sun in the dead of northern winter
clearly shows that the solar distance has nothing to do with the
seasons, which are caused entirely by the tilt of the Earth's
axis relative to the perpendicular to its orbit. That perihelion
is close to the time of Winter
Solstice passage is entirely coincidental.
Though spring is usually considered to be "Galaxy Time," when the
dust of the obscuring Milky Way
is out of the way, the early evening of fall and early winter are
fine times to note the two closest large galaxies to Earth, M 31 in
Andromeda, which is nicely
visible to the naked eye, and M 33 in
Triangulum, which lies between Mothallah (Alpha Trianguli) and Mirach (Beta Andromedae), but
requires excellent eyesight and a very dark sky, the two roughly
two million light years away. Later in the evening, winter skies
are dominated by the beauty of the bright winter stars that feature
Orion, Taurus, Auriga, Gemini, and Canis Major, the latter holding the brightest star of
the sky, Sirius.
