Skylights featured three times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
.
Photo of the Week.. Earthly flower, celestial sky.
Astronomy news for the week starting Friday, August 27, 2004.
This is the week of the full
Moon, the phase reached almost at the end of the month, on the
night of Sunday, August 29. The concept of the month comes from
the moon's 29.5-day
phase cycle. In the civil calendar,
the month is stretched so as to fit 12 cycles into one year. As a
result, individual phases creep forward through the months: the
full Moon in September, for example, will take place on the 28th.
The rest of the week sees the Moon waning through its gibbous
phase, rising ever later after sundown. As it travels through
the constellations of the Zodiac, it passes north of
Neptune the morning of Saturday the 28th and then north of
Uranus the afternoon of Sunday the 29th.
With Jupiter effectively
gone from view, the evening sky is devoid of bright planets, which
now belong to the morning. Dawn on the morning of Tuesday the 31st
presents an excellent sight, with Venus and
Saturn
in near-conjunction with each other. Both off the eastern edge of
classical Gemini, Venus is
vastly the brighter, its amazing glow unmistakable. Saturn will be
just up and to the left. Watch for a few days before and after the
event to see the two approach each other, greet, and then depart,
Venus moving rather quickly to the east relative to the much
fainter ringed planet. While the two seem close together, their
proximity is but an artifact of alignment as seen from Earth
. At a distance of 9.7 Astronomical Units from Earth (the AU
the average distance between the Earth and the
Sun), Saturn is a dozen times farther away than Venus,
explaining Saturn's relative faintness. While admiring the
conjunction, note the surrounding stars. Up and to the left of the
pair lies Pollux in Gemini, while
down and to the right is bright Procyon in Canis Minor, the smaller of Orion's two hunting dogs, the Hunter himself now nicely
visible as well in early morning skies.
Venus is so bright that it is quite visible in broad daylight. In
a clear blue morning sky, look about 45 degrees to the right of the
Sun and very high (after hiding the bright Sun behind something),
and see if you can find a brilliant white dot. Daylight location
can be difficult, as the eyes tend to defocus when looking at a
blank sky. When found, daytime Venus is unmistakable. Then you
look away and it is lost.
Even without planets, the evening sky still holds stellar delights.
We are in the middle of the high progression of constellations that
begins with Bootes (marked by
orange Arcturus) to the west,
and then continues toward the east through Corona Borealis (the Northern Crown), Hercules, Lyra (with brilliant Vega nearly overhead at 9 PM Daylight
Time), to Cygnus (the Swan) with Deneb at its tail. With Altair to the south, Vega and Deneb
compose the Summer Triangle.
Well to the east of Cygnus lie the harbingers of the coming fall,
Pegasus and Andromeda, while rising in the
northeast are Cassiopeia and Perseus.
