The Jovian Planets Chapter 7

Topics Jupter, Saturn, Uranus, Neptune How do we know? Why do we care? What is common about the outer planets? What is peculiar to each of these planets?

Jovian planets (Jupiter-like)

Size radius is about 1/10 of the radius of the Sun

Distance from the Sun Jovian Terrestrial

Terrestrial Jovian Size orbit at 0.4 to 1.5 AU orbit at 5 to 30 AU few small--1/100 radius of the Sun large --1/10 radius of the Sun Size orbit at 0.4 to 1.5 AU orbit at 5 to 30 AU Location Moons few many (# growing) none all have rings Rings Composition rocks and metals gasses and ice

Composition 0.71 to 1.67 g/cm3 So what are they made of? mostly gasses (hydrogen, helium) and ice

Jupiter largest planet Great Red Spot studied by Pioneer, Voyager 1 & 2, Galileo spacecraft liquid interior (very high pressure and temperature) 16 moons (4 largest are the Galilean moons)

Io Active volcanoes

Europa subsurface ocean cracked ice

Ganymeade lots of faults strong magnetic field

Callisto old surface (meaning that it’s not undergoing lots of change except for impact craters)

Saturn Large, thin rings Rings are held together by the gravitational attraction of “shepharding” satellites Major Gaps: The Cassini and Enke divisions

Titan larger than Mercury has an atmosphere probably has oceans of methane

Uranus discovered in 1781 shows no cloud banding axis of rotation is only tilted 8 degrees from the ecliptic 84 year orbital period rings originally discovered during occultation of a star young rings (what’s the source of dust?)

Neptune noted by Galileo the exact path of Uranus could not be explained by the gravitational pulls of the Sun, and the other planets. What does this mean? discovered in 1846 164 year orbital period strong magnetic field

Triton density 2.1 g/cm3 atmosphere (nitrogen) impact craters due to comets ice made of water active ice volcanoes retrograde orbit (it’s going the wrong way) probably captured by Neptune

Extrasolar planets How many planets have we discovered besides those in our solar system? I’m starting to lose count, but it’s now over 100. Planets are even found in binary star systems. We analyze the wobble in a star by studying the Doppler shift in its spectrum and determine the approximate masses and distances of the orbiting planets.

How do we know? How do we know that the outer planets are mostly gas and mostly made up of hydrogen and helium? How do we know that the atmosphere of a planet has methane? How do we know the period of rotation of the outer planets? (Note: we use a different technique of measuring rotational period of the terrestrial planets.) How do we know that a moon’s surface is ice? How do we know the size of matter within the rings? How do we know that a moon has an “old” surface and that the moon has little geologic activity?