Photo of the Week. The long lake seen through the
large left-to-right break in the clouds is the southeastern arc of the
great
Manicouagan impact crater in northern Quebec. One hundred
kilometers (62 miles) across, it was created by the collision of an
asteroid with Earth 214 million years ago, and now appears as a
water-filled ring. (See it at full
resolution.)
Astronomy news for the week starting Friday, August 25, 2006.
The evening Moon is upon us this week as it grows in the waxing crescent phase (the nighttime
side aglow with Earthlight
) to
first quarter the last night of the month, that phase passed
the evening of Thursday, August 31. If there are two full Moons in
a month, the second is called a "blue Moon" (in part because it has
no formal monthly name). August 2006 was a month for two first
quarters, but somehow "blue quarter" does not seem to work as well.
The night of Sunday the 27th, the crescent will be just to the
southwest of Spica in Virgo. For a better sight, be sure
to look the night of Wednesday the 29th, when a fatter crescent
will pass five degrees south of Jupiter (the angle between the front bowl stars of the
Big Dipper). Then the night of
Thursday the 31st, the first quarter takes on (passing just south
of) Antares in Scorpius. The stellar passages are so
close that the Moon will actually occult Spica and Antares as seen
from parts of the southern hemisphere.
Planetary events feature first
Venus and Saturn, which
come into close conjunction with each other the night of Saturday
the 26th, but out of sight for North America. The morning of the
26th, Venus will rise above Saturn (in twilight, around 5 AM),
while the following morning they will have reversed themselves.
Venus, always bright, is sadly disappearing from view, while the
ringed planet will rapidly rise out of dawn. Next comes Mercury, which passes
superior conjunction with the Sun the night of Thursday the 31st as
it heads towards a poor apparition in the evening sky. Finally, Jupiter is
planetary king of evening, indeed all there is (Mars well
out of the way in bright twilight), the giant of the Solar System not setting
until about 10:30 PM.
There is still plenty of time to admire Scorpius, which appears low
to the south as evening begins. To the west lie more southerly Lupus (the Wolf) and Centaurus (the Centaur), the latter
directly south of Arcturus.
While effectively invisible now from temperate North America, the
constellation still presents a fine sight from the temperate
southern hemisphere, much as the Big Dipper and Bootes do for us back in the north.
Look then to the east of Scorpius to find Sagittarius (quickly identified by its upside-down
Little Milk Dipper), which holds a special place in the brightest
part of the Milky Way.
