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From: dipper@utastro.UUCP (Debbie Byrd)
Newsgroups: net.astro
Subject: StarDate: September 23 Jupiter and the Moon
Message-ID: <749@utastro.UUCP>
Date: Mon, 23-Sep-85 02:00:38 EDT
Article-I.D.: utastro.749
Posted: Mon Sep 23 02:00:38 1985
Date-Received: Wed, 25-Sep-85 11:02:04 EDT
Organization: U. Texas, Astronomy, Austin, TX
Lines: 43


The moons of Jupiter sometimes eclipse each other.  More -- after
this.

September 23  Jupiter and the Moon

If you look outside this evening, you'll see a very bright object near
the moon.  It's not a star -- it's a planet, Jupiter.

Jupiter looks tiny compared to our moon -- but it's the largest world
in our solar system, with at least sixteen moons of its own.  You can
see some of these moons if you look at Jupiter with binoculars.  Just
be sure to steady the binoculars somehow -- prop your elbows on a fence
or a car -- as you look toward Jupiter -- near the moon in tonight's
sky.

This point of light -- this giant world, Jupiter -- orbits the sun in
nearly the same plane as the Earth.  Jupiter's moons also orbit near
that same plane -- so we often see eclipses as the moons pass behind
Jupiter -- and sometimes eclipses of the jovian moons by each other.
There are some eclipses of moons by moons going on this week.  Tomorrow
night, the shadow of the moon Ganymede will fall on Callisto.  Those
watching this event through a telescope will see Callisto fade in
brightness as Ganymede's shadow moves across it.  Wednesday night,
it'll be the innermost Jovian moon Io that'll skim through Ganymede's
shadow.

You need a telescope to get a good look at the moons of Jupiter --
dimming and brightening as they eclipse one another this week.  But to
see Jupiter itself, just use your eyes.  Look for the bright object
near the moon tonight.  After tonight, the moon will move on past
Jupiter.  But the planet is brighter than any star.  It'll be easy to
see in our evening sky through early 1986.



Script by Deborah Byrd.





(c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin


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