Photo of the Week. A flowering tree glorifies the blue sky.
Astronomy news for the week starting Friday, October 10, 2008.
A quiet week. Yet given the turmoil of daily life, there is
something to be said for that. And with the full Moon, we can hardly see the stars, making it even quieter.
Yet there is always the full Moon itself.
While with its brilliant light it can be an annoyance to
astronomers, it remains a charming, even poetic, sight.
We start the week with the Moon in its waxing gibbous phase. Passing formal full phase the afternoon of
Tuesday, October 14, the full Moon thus rises just after sunset.
It then enters the waning gibbous phase, and passes perigee, where
it is closest to the Earth, at the end our week. The morning of
Friday the 17th, the Moon also passes against the background of the
Pleiades star cluster, though,
with the lunar disk so bright, you can't see much without a
telescope.
So bright as to allow us nearly to read by its light, the full Moon
is full of cultural references, so much so that full Moons are
named by a number of cultures. Since the evening eastern ecliptic lies flat against the
horizon, the delay in full-Moonrise from one night to the next is
at a minimum in September. The Moon thus floods the early evening with
Moonlight, hence the "Harvest Moon." The one in October -- the
Hunter's Moon -- is not all that much different. That the full
Moon seems to rise huge is, sadly, but an illusion caused (some
say) by our eye referring it to things on the horizon. The
sometime-coppery color comes from absorption of Moonlight by the
Earth's atmosphere, the same thing that causes red sunrises. This is the best time
to see the "Man in the Moon," the pattern caused by huge, ancient,
lava-filled impact basins on the lunar surface, the "maria," which always face us, the Moon not
rotating with respect to the Earth, the result of tidal slowing and
locking.
Though
Venus now does not set until the end of evening twilight, it is
still a bit elusive (though readily visible if you look early
enough). On the other hand, Jupiter, bright in the southwest until late evening,
not setting until 11 PM, is obvious. The morning sky, for some
time now planetless, is beginning to show promise, as Saturn, rising
around 4:30 AM, has become quite visible in central Leo well to the east of Regulus.
Moving off now into the northwestern sky are the gang of five that
stretch from Bootes (with Arcturus) through Corona Borealis (the Northern Crown),
Hercules, Lyra (with Vega), and Cygnus (topped by Deneb). Cygnus lies
in the heart of the northern Milky
Way, the white band of light spilling southward through Aquila into Sagittarius and beyond.
