Skylights featured five times on Earth Science
Picture of the Day: 1
, 2
, 3
, 4
, 5
Photo of the Week. Silver linings bring peace to a
turbulent sky.
Astronomy news for the week starting Friday, December 9, 2005.
The Moon, having passed first quarter last Thursday, December 8,
grows through its
waxing gibbous phase toward full,
that phase reached at the end of Skylights' week on Thursday the
15th during daylight morning hours in North America. The night of
Wednesday the 14th, the Moon will therefore rise not quite full just before
sunset, whereas the following night it will rise just after sunset
and just past full.
Speaking of which, the earliest sunset took place around December
7. Even though the days will keep getting shorter until the
passage of the Sun across the Winter
Solstice in Sagittarius on
December 21, the Sun will begin to set later, the difference
compliments of the tilt of the Earth's axis and the eccentricity of
its orbit.
The week is filled with planetary events. Topping the list, Venus
hits its greatest brilliancy for this current orbital pass on
Friday the 9th. Though presenting mostly its nighttime side in a
distinct crescent phase (visible only
telescopically), the planet is so close to us (60 million
kilometers, 38 million miles) that it is still 18 times brighter
than the brightest star, Sirius.
Though at the beginning of the week not setting until around 7:30
PM, Venus will from here on out quickly disappear, by the end of
the year setting an hour earlier, just as twilight ends. On the
other side of the sky and the night, Venus's brother planet Mercury is for
now at its best, reaching greatest western elongation (21 degrees
to the west of the Sun) on Monday the 12th and rising in the east-
southeast just as dawn breaks. If you cannot find Mercury, you
surely can admire very bright Jupiter,
which at dawn dominates the southeastern sky, the king of the
planetary system now rising around 4 AM well to the east of Spica.
In between are
Mars and Saturn. The
ringed planet (in Cancer) now rises
in mid-evening, around 8:30 PM, just half an hour before Mars (in
Aries) transits the meridian to
the south. Mars then sets as Jupiter rises. As the Earth
pulls away from it, Mars is fading some, and ceases retrograde motion on Saturday the 10th. The following night, the
the Moon will
encroach upon it from the west. If it is not cold enough for you
here, the Moon will occult
Mars as seen from northeastern Siberia.
Keep your eye out for meteors from the Geminid shower (the debris of
the defunct comet 3200 Phaeton), which peaks the morning of Tuesday
the 13th. The bright Moon will unfortunatly blot out much of the
show.
The autumn stars begin to slip away. By mid evening, the Great Square of Pegasus is to the west of the
meridian, while to the southeast of it, Pisces (hardly visible in bright moonlight) straddles
it. To the southeast of Pisces, Cetus the Sea Monster swims the mythical seas, while
farther down in the same direction winds Eridanus, the River, which ends far to the south in the bright blue star Achernar.
