Astronomy news for the week starting Friday, August 7, 2009.
Most of the week sees the waning
gibbous Moon, which, rising ever later before midnight, finally
reaches its third
quarter on Thursday, August 13, during daylight hours, but just
after Moonset in North America. The morning of Friday the 14th, we
then will see the first part of the waning crescent. The Moon's only
planetary passage is well to the north of Uranus on Sunday
the 9th.
Since last March, we've watched Jupiter first
coming on to the scene, then rising ever earlier until early last
June it began rising after local midnight. It now comes full bore
onto the nighttime sky, as the giant planet passes opposition with
the Sun during the day on Friday the 14th, making the view on the
nights of Thursday the 13th and Friday the 14th about equal. On
these nights, Jupiter will rise at sunset, set at sunrise, and
cross the meridian to the south at
local midnight (1 AM Daylight Time). With the Earth passing right between
Jupiter and the Sun,
the King of the Planetary System is also in maximum
retrograde motion, to the west against the background of the
relatively faint stars of northeastern Capricornus, to the north of Nashira and Deneb Algedi (Gamma and Delta
Capricorni) as well as just to the southwest of Neptune, which
passes opposition with the Sun next week.
While Jupiter dominates the scene, Saturn, which
sets in late twilight, slips away. It'll be back in the morning
sky in mid-October. Mercury, now in
the west and setting in mid-evening-twilight, is an even tougher
find. The current mornings are now reserved for Venus and Mars. The red
planet, now mid-first magnitude and rising around 1:30 AM Daylight,
will be heading toward the horns of Taurus (Beta and Zeta Tauri) as if they were a pair
of goalposts. With Mars now rising earlier and Venus rising later,
the gap between the two of them grows. Brilliant Venus, though,
remains a most excellent sight as it comes up just after 3 AM
near the feet of Gemini to
the southwest of Castor and Pollux.
The biggest event of the week is the return of the annual
Perseid meteor shower, which in North America peaks during the
daytime of Wednesday the 12th, making the mornings of the Wednesday
the 12th and Thursday the 13th the times to watch (mornings far
better than evenings). Even though the third quarter Moon will
light the sky, you should be able to see a few meteors. While the
meteors seem to come out of Perseus, the best direction to look is overhead. The
shower is from the leavings of Comet
Swift-Tuttle, which has a 130 year period around the Sun and last
came by in 1992, so the shower is diminishing some.
Some of the great constellations
lie in the far south and are thus almost invisible to people in the
northern hemisphere unless they have great horizons. Think, for
example, of winter-spring's Argo,
with only Puppis (the Keel of the
Ship) readily visible to northerners to the southeast of Canis Major and Sirius. In the northern summer, we
have Centaurus, the Centaur,
which lies south of Virgo's Spica and to the west of Scorpius, with Lupus in between. From the southern hemisphere, Centaurus is glorious to the east of
Crux, the Southern Cross.
