SKYLIGHTS
Astronomy news for the week starting Friday, August 4, 2000.
Now that the Moon is done eclipsing the Sun, we begin the week with
its waxing crescent phase, as it heads toward first quarter on the
night of Sunday, August 6th, thereafter moving into its waxing
gibbous phase. The night of Friday, the 4th, it will be to the
northwest of the star Spica in Virgo, the night of Saturday the 5th
to the northeast of it; the night of Tuesday, the 8th, the Moon
will stand above Antares in Scorpius.
The evening remains planetless -- at least in terms of naked-eye
planets -- but not for long, as Venus slowly begins to rise out of
bright western evening twilight. Still a difficult object to find,
the view will improve during the month to come. The planet will
pass close to Regulus in Leo on Sunday, the 6th. Better are the
morning hours, with Jupiter and Saturn, both now in Taurus not far
from the Pleiades, and both rising just after local midnight (1 AM
daylight time). Not that is much matters, as both are too close to
the morning Sun to be visible, but Mercury and Mars pass each other
very closely (in angle, not distance), less than 0.1 degree, on
Thursday, August 10. The evening does better if we go to the
telescope. Though Uranus is technically naked-eye, it is faint and
hard to find. Still in Capricornus, it passes opposition with the
Sun around midnight (in North America) the night of Thursday, the
10th. Both Uranus and Neptune (a bit to the west of Uranus) are in
retrograde, or backward motion.
This week marks the buildup to everyone's favorite meteor shower,
the Perseids, which will be at their best the morning of Saturday,
August 12, when they will produce up to two meteors per minute.
But the show goes on this week as well, the shower also visible at
a lower level the morning of Friday the 11th (as well as earlier in
the week). Though the meteors will appear to come from the
constellation Perseus, they are best seen overhead, and in the
morning hours when we face in the direction in which the Earth
moves. The Moon will unfortunately compete this year, but there is
still a short period between moonset and morning twilight when the
sky will be dark. Most meteors are dusty-rocky debris from
evaporating comets. When the orbiting Earth passes close to a
comet's orbit, we pick up larger-than-usual amounts of the stuff,
and the result is a shower of meteors. Since the meteors are on
parallel paths, we see a perspective effect in which they seem to
come from a point in the sky (rather like railroad tracks seeming
to converge in the distance). The Perseids come from Comet Temple-
Tuttle, which has a period around the Sun of 120 years and made its
last appearance in the inner Solar System in the early 1980s.
