STARGAZER for August 23, 2008

Evening Sky Full of Planets

Now is a good time for evening stargazers to view four of the five naked-eye
planets.

The easiest is Jupiter which dominates the southern sky in the early
evening. Far outshining all stars, Jupiter is the third brightest night sky
object
behind only the Moon and Venus.

While Jupiter appears as a bright star to the naked eye, most binoculars can
reveal its disc-like shape. And if the binoculars are held very steady, up
to four of Jupiter's moons can be seen looking like tiny stars in alignment.

On any given night, however, all four may not visible since, as they orbit
Jupiter, one or more might be hiding behind or in front of the huge planet.
These four largest of Jupiter's many moons--Io, Europa, Ganymede, and
Callisto--are called the Galilean Moons in honor of Galileo who discovered them
with
his new telescope in 1610. They are only slightly larger than our moon, but
1,500 times further away.

Jupiter is now up when the skies darken and doesn't set until the wee hours
of morning, so you can watch it all evening. Not so with the other three.

Mars, Venus and Mercury are low in the west at dusk and set before the sky
gets completely dark, so don't linger. Start looking 30 minutes after sunset.
If you have binoculars, use them, and since the planets are quite low, you'll
need a clear view of the western horizon.

Of the three Venus is by far the brightest and easiest to spot. Once you've
found Venus, look for fainter Mercury three moonwidths to the lower left.
Again, binoculars will help, especially for those (like me) with aging eyes.

Fainter Mars is 10 degrees to their upper left. (Remember, the width of your
fist held at arm's length is 10 degrees.)

After you've found them, keep watching them nightly as this is a show that
changes each evening.

For the next week or so Venus and Mercury stay in about the same position
relative to each other as they gradually approach Mars. The evening of Aug. 31,
a thin crescent Moon visits the planetary trio. By Sep. 4, the planets form
a nearly equilateral triangle with brilliant Venus to the right, Mercury to
the lower left and Mars to the upper left.

In what might be the show's climax, Venus passes less than a moonwidth from
Mars Sept. 11. After that, Mercury and Mars sink into the setting Sun and
Venus begins asserting herself as the "evening star" where she will remain
until
well into 2009.

Maybe you've noticed there's been no mention of Saturn. The ringed planet,
which has been gracing our evening sky all year, is now hidden in the glare of
the Sun. Sep. 3 it reaches conjunction with the Sun--astronomers' way of
saying it is exactly on the other side of (behind) the Sun. By October it will
have moved into the morning sky.

Next Two Weeks. Avg. sunrise: 7:03 a.m.; avg. sunset: 7:55 p.m. (exact for
Waco, TX)

* Tonight the Moon is at 3rd quarter.
* Thurs. morning the crescent Moon is three moonwidths above the Beehive
cluster low in the east shortly before dawn.
* The Moon is new Aug. 30.
* The evening of Sep. 2, the crescent Moon is below the star Spica.

Star Party. The Central Texas Astronomical Society's free monthly star party
is tonight at the Waco Wetlands beginning at 8 p.m., weather permitting. For
directions see my Website.

=======================================================


Stargazer appears every other week in the Waco Tribune-Herald and other
Texas newspapers. Paul Derrick is an amateur astronomer who lives in Waco.
Write him at 918 N. 30th St., Waco, TX 76707, call or fax at (254) 753-6920, or
e-mail at paulderrickwaco@....

Copyright 2008 by Paul Derrick. Permission is granted for free electronic
distribution as long as these paragraphs are included. Please obtain
permission from the author for publication in any other form. To be added to
(or
removed from) the free e-mail distribution list, send your e-mail address (and
name) to _paulderrickwaco@..._ (mailto:paulderrickwaco@...) .


* * See the Stargazer Web site at http://www.stargazerpaul.com. * *





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