Sunday, July 13, 2014


Order from Sun: 5
Named For: Roman king of the gods
Diameter: 86,880 miles
Volume: 1321x Earth
Gravity: 2.53x Earth
Distance from Sun: 483 million miles
Orbital Period: 11.86 Earth years
Orbital Inclination: 1.30 degrees
Orbital Eccentricity: .048
Length of Day: 9.92 hours
Temperature: -234F
Composition: Gasses
Atmospheric Composition: hydrogen, helium
Moons: 67+
Rings: Yes, thin
Notable Exploration: Pioneer 10, 11 (1973-4), Voyager 1 and 2 (1979), Galileo (1995-2003)

Jupiter is the largest planet in the solar system and, because of its great distance, shines at a relatively constant -2.5 magnitude. Because of its twelve year orbit, Jupiter takes spends about a year in each zodiac constellation before moving on to the next. To the naked eye, Jupiter appears only as a bright star.

 With optical aid, the game changes dramatically. In binoculars, while the cloud bands will still be invisible, one should be able to see the 'Galilean Moons,' named after their discoverer, the Italian astronomer Galileo. These four largest moons of Jupiter are named Io, Europa, Ganymede, and Callisto and are in that same order, with Io being closest to Jupiter and Callisto farthest. A simple way to remember them is to say 'I(Io) Eat(Europa) Green(Ganymede) Caterpillars(Callisto).' Okay, it's a little juvenile, but it works. For historical implications, the discovery of Jupiter's moons proved that not all objects went around the Sun, which was preached as gospel by science and Church until that time. Also, in binoculars, Jupiter transforms from looking like a bright star into a very obvious planetary disc. To see this, just look at the edges of the planet, which appear as a crisp line and not a diffuse glow.

 In telescopes, Jupiter transforms from a featureless disc into a world alive with color. In even small telescopes, one can see distinct, reddish-pink cloud bands on the planet. The higher the power, the more detail one can resolve. In large scopes under steady skies, expect to see, with relative ease, swirling in the clouds along with the Great Red Spot. Another cool feature to be seen in a telescope at high power is the shadows of the Galilean Moons transiting the disc of the planet itself. Though not overly rare, these are fun events to observe, especially for a beginning astronomer.

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