The Outer Planets Chap 16 Sec 4 Chap

The Outer Planets Chap 16, Sec 4

Chap 16 Sec 4 Essential Questions 1. What characteristics do the gas giants have in common? 2. What characteristics distinguish each of the outer planets?

The Gas Giants

The Gas Giants l The four outer planets l l l l Jupiter Saturn Uranus Neptune Much larger & more massive than Earth Do not have solid surfaces All are composed mainly of hydrogen & helium Their gravitational force is much greater than Earth’s because of their massive size They have thick atmospheres A lot of the hydrogen & helium inside the planets is liquid because of enormous pressure Outer layers of the planets are cold because of their distance from the sun, but temperatures increase inside the planets All have many moons All have rings l A ring is a thin disk of small particles of ice and rock

Jupiter

Jupiter l The largest & most massive planet l Its mass is about 2 ½ times all other planets combined l Atmosphere: l Thick atmosphere of mainly hydrogen & helium l The Great Red Spot – a giant storm larger than Earth. Swirling winds blow hundreds of miles an hour, similar to a hurricane, but it has lasted for 350 years and doesn’t appear to be weakening

Jupiter l Structure: l. A dense core of rock and iron at the center l The core is surrounded by a thick mantle of liquid hydrogen & helium l Pressure at Jupiter’s core may be 30 million times greater than the pressure at Earth’s surface l Extreme pressure is caused by its thick atmosphere

Jupiter’s Moons Remember Galileo discovered the largest four l Many more have been discovered as technology improved – latest count is more than 63 l The four largest are all very different from each other and are all larger than our Moon l

Jupiter’s Largest Moons Io – its surface is covered with large, active volcanoes. Sulfur gives it an unusual color. l Europa – it has an icy crust and scientists suspect it has an ocean of liquid water underneath the ice l Ganymede – the largest moon in the solar system is larger than Mercury or Pluto l Callisto – has an icy, cratered surface l

Io

Ganymede

Europa

Callisto

Saturn

Saturn The second-largest planet l Has a thick atmosphere of hydrogen & helium l Atmosphere has thick clouds and storms – though not as spectacular as those on Jupiter l The least dense planet (less dense than water) l The Voyager probes provided lots of information about Saturn l

Saturn’s Rings l Saturn has the most spectacular rings of any planet l The rings are broad and thin – like a CD l The rings are made of chunks of ice and rock, each traveling in its own orbit around Saturn

Saturn’s Moons Saturn is currently known to have more than 60 moons l The largest is Titan l l It has a very thick atmosphere (so thick that light can hardly pass through) l There are four other moons that are larger than 1, 000 kilometers in diameter

Two views of Titan From Far Away Very Close Up with special Lens

Uranus

Uranus It is about four times the diameter of Earth, but much smaller than Jupiter and Saturn l It is twice as far from the sun as Saturn, so it is much colder l Has a unique blue-green color because of methane gas in its atmosphere l Its rings are thin, flat, and much darker than Saturn’s l It was the first planet discovered since ancient times l l Discovered in 1781 by Willam Herschel in England

Unique Features of Uranus In the 1980 s (200 years after being discovered) Voyager 2 arrived at Uranus and sent back close-up pictures l It has few clouds, but astronomers calculated it rotated in about 17 hours l Uranus is tilted on its side l It rotated top to bottom instead of side to side like other planets (and its rings and moons rotate around its tilted axis) l Scientists think it was hit by an object billions of years ago that knocked it on its side l

Uranus’s Moons Uranus has at least 27 moons l Voyager 2 discovered the five largest moons have icy, cratered surfaces and lava flows l

Neptune

Neptune is similar in size and color to Uranus l It is a blue color because of methane in its atmosphere l Because it is so far from the sun, it is very cold l It has clouds and storms in its atmosphere l l Scientists think the clouds and storms are happening because the planet is slowly shrinking and causing the interior to heat up

Discovering Neptune l Neptune was discovered by mathematics – astronomers noticed Uranus’s orbit wasn’t the exact path it should be and predicted an unseen planet was disturbing Uranus’s orbit l By 1846 scientists had calculated the orbit of the unseen planet – soon after, Neptune was identified

Flying by Neptune In 1989 Voyager 2 flew by Neptune and photographed the Great Dark Spot (a storm about the size of Earth) l Storms come and go on Neptune which tells us it has an active atmosphere l

Neptune’s Moons Neptune has at least 13 moons l The largest is Triton l l It has a thin atmosphere l Its south pole is covered in nitrogen ice

Pluto is not a gas giant l It is much smaller and denser than the outer planets and has a solid surface l l l Pluto is so far from the sun that it takes 240 Earth years to revolve around the sun once l l Pluto is smaller than our Moon Its orbit is very elliptical and it crosses inside Neptune’s orbit for part of its revolution Moons l Pluto has at least three. The largest is Charon and is more than half as big as Pluto

Dwarf Planets Dwarf planets are round and orbits the sun, like a planet, but it has not cleared out the neighborhood around its orbit l Dwarf planet classification was created in 2006 when an object larger than Pluto and farther from the sun was discovered l At that time Pluto was reclassified as a dwarf planet and there are two others l

Video

Essential Questions - Answered 1. What characteristics do the gas giants have in common? l l l No solid surface Thick atmosphere made mostly of hydrogen & helium A set of rings Very Large & massive Rotates quickly, revolves slowly

2. What characteristics distinguish each of the outer planets? Jupiter – largest & most massive planet, Great Red Spot, most moons (63+) Saturn – second largest planets, best rings, least dense planet Uranus – blue-green color, rotates on its side Neptune – blue color, lots of storms Pluto – solid, rocky surface; no longer a planet