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See IoFlyby.com for details.
This is a good time to look at Jupiter through a telescope. Jupiter will appear to be nearly 50 arc seconds in diameter, approximately 36 times smaller than the full moon. That's big! Even inexpensive department store telescopes will be powerful enough to reveal light and dark bands crossing Jupiter's equator and Jupiter's four largest moons: Io, Europa, Ganymede and Callisto. It's also a good time to view Jupiter's famous Great Red Spot, a gigantic storm system that has been churning for at least 300 years. Tonight, October 22, the Red Spot will move across the center of Jupiter's disk, as seen from Earth, around 9:19 p.m. EDT. A six-inch or larger telescope and good viewing conditions are recommended for seeing the red spot. The Galilean satellites can easily be seen through a good pair of binoculars. (As an interesting exercise, see how steadily you can hold the binoculars as you're viewing Jupiter. It's not as easy as it sounds!)  Left:
This Hubble Space Telescope image of Jupiter shows a hurricane
twice the size of the Earth. It has been raging at least as long
as telescopes could see it, and shows no signs of slowing. It
is Jupiter's Great Red Spot, the largest swirling storm system
in the Solar System. Like most astronomical phenomena, the Great
Red Spot was neither predicted nor immediately understood after
its discovery. Still today, details of how and why the Great
Red Spot changes its shape, size, and color remain mysterious.
[More]
If you're out this weekend admiring Jupiter, don't forget that NASA is watching the giant planet, too, although with a better view. NASA's Galileo spacecraft has just marked the tenth anniversary of its launch aboard the Space Shuttle Atlantis on October 18, 1989. Galileo entered orbit around Jupiter in December 1995. Since then it has revolutionized our understanding of Jupiter and its moons by sending a probe into Jupiter's atmosphere, finding new evidence for water on Europa, and most recently zipping a mere 600 km above the volcanoes of Io. Many of Galileo's impressive accomplishments are described at JPL's new Galileo home page: http://galileo.jpl.nasa.gov. The current Galileo Extended Mission will conclude later this year with a daring pass less than 300 km above Io, possibly flying through the plume of a sulfurous volcano. For more information about the Io flybys, please visit IoFlyby.com.  |
October 22, 1999: Lately, you
may have noticed a bright light in the sky that rises above the
eastern horizon around dinnertime. It's not an airplane or a
UFO -- it's Jupiter, the largest planet in the solar system.
This weekend Jupiter will be brighter and closer to the Earth
than it has been for a dozen years. 
Left: When Jupiter is at opposition
it is directly opposite the Sun as seen from Earth. Compared
to Earth, which zips around the sun once a year, Jupiter completes
one circuit around the Sun rather slowly, once every 12 years.
Opposition takes place about once per year as the Earth speeds
by the slower-moving giant planet. 
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This week's sky at a glance -- from Sky & Telescope Jack Star Gazer -- Jack Horkheimer's naked eye astronomy web site Jupiter - from the SEDS Nine Planets web site Saturn - from the SEDS Nine Planets web site |
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