Photo of the Week.. Planet Earth: Like Venus and
Mars, Earth is covered with volcanos, this one Osorno in Chile.
Astronomy news for the week starting Friday,
August 30, 2002.
The Moon begins the week in its last
quarter, the phase reached on Friday, August 30, shortly before
moonrise in the Americas. It thereafter wanes through its crescent
phase, appearing ever-closer to the eastern horizon at dawn. As it
orbits Earth, the Moon can be found close to and to the northwest
of Saturn
the morning of Sunday, September 1, and well to the northeast of
the ringed planet the following day, Saturn now rising in Taurus shortly after midnight,
consistent with its proximity to the third quarter Moon. The
morning of Wednesday, the 4th, the Moon (which will be rather well
north of the ecliptic) will pass north of the giant planet
Jupiter, which now rises in Cancer about 3:30 AM, Jupiter pulling steadily farther
from more slowly moving Saturn.
The inner planets have events of their own. The night of Friday,
August 30, Venus,
brilliant in western evening twilight, makes a close pass to the
south of the first magnitude star Spica in Virgo. Venus's low position and the brightness
contrast between the two will make the conjunction somewhat
difficult to see. Mercury
then passes its greatest eastern elongation, when it is 27 degrees
to the east of the Sun,
on Sunday, September 1. Greatest elongations are clearly the best
time to see the small planet. Unfortunately, this one is rather
poor, as the ecliptic is so flat against the horizon in western
evening skies that Mercury is very low and nearly lost in bright
twilight.
As September arrives and the Sun approaches the autumnal equinox in
Virgo, the shortening of the days
is quickly accelerating and noticeable nearly from one day to the
next. Depending somewhat on location, twilight is over and the
sky fully dark by 9 PM, while morning twilight does not commence
until almost 5 AM (all Daylight Time). The acceleration in times
will continue until September 22, when autumn begins in the
northern hemisphere.
Scorpius is to late summer as Orion is to winter, the two opposite
each other in the sky. Look to the south as evening begins to see
bright Antares and, if you are
far enough south, Scorpius's curving tail. Both constellations are
filled with massive bright blue-white stars that are related to
each other in loose unbound (that is, expanding), "associations."
Most of these constellations' stars were born about the same time
(on an astronomical time scale), and many will expire about the
same time, the more massive ones (including Antares, which has
evolved from a blue-white star into a huge red supergiant) will
explode in grand supernovae.
