15_Jupiter_Moons - GEL36 SOLAR SYSTEM Lecture 15: Jupiter &...

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1 GEL36 SOLAR SYSTEM Lecture 15: “Jupiter & the Galilean Moons” (Ch.23) Goal of the Lecture: To understand Jupiter as a prototypical ‘gas giant’ to compare with the other giant Jovian planets. Jupiter shines in the east just before dawn, along with Venus, Mars & Mercury. Look at it with binoculars or a telescope and you’ll see three or four bright dots surrounding it – those are the Galilean moons. Dimensions and orbital characteristics in the ‘70’s and Voyager 1 that were launched in 1977. Voyager 2 visited all 4 Jovian planets before flying out into space in 1989. The Voyager 1 spacecraft is now out near the heliosheath, about 110 AU from the sun in the region where the solar wind begins to interact with interstellar space. In December 1995, the Galileo spacecraft reached Jupiter and orbited the planet and its Galilean moons, mapping and taking measurements. - Galileo plunged into Jupiter’s crushing atmosphere on Sept. 21, 2003. Jupiter is big and massive . . . Jupiter is by far the most massive of the planets, containing almost three-fourths of all the mass of the planets. - Jupiter is about 11 times the diameter of the Earth, and has about 318 times the mass. (Jupiter is 1/100th the mass of the sun.) All of the Jovian planets are large because of the process of gravitational collapse . When a planet has grown to a mass of about 10-20 Earth-masses, it has enough gravity to capture gas directly from the solar nebula and a high enough escape velocity to hold on to those light gases. Jovian planets grew initially by the accretion of enormous amounts of rock and ice, followed by gravitational capture of H and He. (see earlier notes on planetary evolution from the solar nebula) Orbit and spin . . . - prograde orbit, prograde spin. - one Jupiter year takes ~12 earth years (orbital period) - orbit is inclined ~ 1° from the ecliptic.
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2 - one Jupiter day takes only 10 hours (2.5 times faster than Earth), which contributes to its shape being oblate - 6% wider near the equator than from pole to pole. Flattening due to rapid rate of spin and “fluidity” of the hydrogen. Composition Density is 1.34 g/cc - just above the density of water (1), but well below typical densities of rock (2.5-4). (Earth’s density = 5.5) - mostly liquid composition, rather than gas (contrary to its designation as a "gas" giant) - spectra from Earth and from spacecraft show that the composition is very similar to the sun’s - mostly hydrogen (78%) and helium (19%) with traces of methane (CH 4 ), ammonia (NH 3 ) and water. - no actual ‘surfaces’ on the Jovian planets From the outside to the inside . . . Pressure, density and temperature all increase toward the interior, like on all other
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This note was uploaded on 05/31/2011 for the course GEL 36 taught by Professor Osleger,d during the Spring '08 term at UC Davis.

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15_Jupiter_Moons - GEL36 SOLAR SYSTEM Lecture 15: Jupiter &...

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