Choosing A Telescope
Telescope Aperture Considerations
Introduction to Planetary Sketching
Refractor Dobsonian Style Mounts
The Bonds: Pioneers of American Astronomy
Saturn's Encke Minima and Encke Division
Nature and Travel Photography
Recommended Astronomy Books
Here is a link of all of my Jupiter drawings and observing reports on my web site.
In the late 1930's, three white ovals formed in Jupiter's South Temperate Belt (STB) and were designated as FA, BC and DE. Ovals BC and DE merged in 1998 formed the oval BE. The above sketch of Jupiter made on October 13, 1999 shows ovals BE and FA. These two ovals merged in March 2000 and formed oval BA.
Since 2000 BA has remained white in color, but at the end of 2005 oval BA began to change to a brown color, and on February 24, 2006 Filipino amateur astronomer Christopher Go noted that its color changed to that of the Great Red Spot. Dr. Tony Phillips gave it the name "Red Spot Jr." or "Red Jr." although professional astronomers still refer to it as oval BA.
The above sketch made December 23, 2001. Note that since the first sketch was made in October 1999 SEB has undergone considerable changes, fading from brown to grey, and becoming bisected by a rift.
October 17, 1987, 0:15 - 0:40 UT, seeing 3 - 4 (0 worst, 5 best), transparency 5. System I Central Meridian 260.7°, System II Central Meridian 62.6°.
*Since Jupiter does not rotate on its axis at a uniform rate, two rotation periods have been assigned to it: System I is 9 hours 50 minutes and 30 seconds, encompassing the Equatorial Zone, which extends from the northern edge of the South Equatorial Belt to the southern edge of the North Equatorial Belt. All other Jovian latitudes, except for the polar regions, have been assigned a rotation period of 9 hours 55 minutes and 40 seconds, which is System II.
**System III is sometimes used to define the polar regions, or alternately is used by radio astronomers to study Jupiter's rotation. For amateur observations only System I and II are used.
Moons of Jupiter
As of March 1012 Jupiter has 63 moons. This includes the Galilean moons that were discovered independently in 1610 by Galileo Galilei and Simon Marius. Although they are known as the Galilean moons it was Marius who gave them their names: Io (pronounced "EYE oh" or "EE oh", magnitude 4.9), Europa (pronounced "yoo ROH puh", magnitude 5.2), Ganymede (pronounced "GAN uh meed", magnitude 4.5), and Callisto (pronounced "ka LIS toh", magnitude 5.5).
The Galilean moons are easily visible in amateur sized telescopes, and I have seen them in a pair of Oberwerk 11x70mm Binoculars. Also I have been able to resolve the moons as disks using a telescope and based on their size and color I was able to identify them.
Io (Jupiter I) is composed of molten silicate rock, and it may have an iron core. Its surface is covered with volcanic calderas, active volcanoes, lava flows, and lakes of molten sulfur. The mechanism for generating these volcanoes is caused by tidal interactions between Io, Europa, Ganymede and Jupiter. Io may have its own magnetic field.
Europa (Jupiter II) is slightly smaller than the Earth's Moon and is the fourth largest of Jupiter's satellites. Like Io it is composed of molten silicate rock, and may have a small metallic core. It has a weak magnetic field. The surface of Europa has a thin outer layer of ice, which is very smooth and crisscrossed by a series of dark streaks. The surface appears to be very young as there are few craters on it. It is possible that beneath the surface ice there is a layer of liquid water (perhaps a salty ocean) kept liquid by tidally generated heat. If so, it would be the only other place in the solar system other than Earth where liquid water exists in significant quantities.
Ganymede (Jupiter III) is the largest moon in the solar system and is larger then the planet Mercury. Ganymede may have its own magnetic field. It is the largest of Jupiter's known satellites, and it is the largest satellite in the solar system. It has a small molten iron or iron/sulfur core surrounded by a rocky silicate mantle with an icy shell on top. Ganymede has a magnetosphere field that is embedded inside Jupiter's larger magnetic field.
Callisto (Jupiter IV) is only slightly smaller than Mercury. It has a very tenuous atmosphere composed of carbon dioxide, and a weak magnetic field, which may indicate some sort of salty fluid below the surface. Callisto is about 40% ice and 60% rock/iron, and is probably similar to Saturn's moon Titan and Neptune's moon Triton. Callisto's surface is very old and covered with craters like the highlands of Mars and the Moon. This includes a long series of impact craters in a straight line which may have been caused by an object that was tidally disrupted as it passed close to Jupiter (as happened when Comet P/Shoemaker-Levy 9 fragments impacted Jupiter in July 1994) and then impacted on Callisto.
Article © 2000 - 2015, Eric Jamison, All rights reserved.
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