Presentation on theme: "Uranus was discovered in 1781, but its rings were not found until 1977"— Presentation transcript:
1Uranus was discovered in 1781, but its rings were not found until 1977 Uranus was discovered in 1781, but its rings were not found until Like Uranus itself, the rings were discovered by accident. This false-color infrared image was taken by the Hubble Space Telescope.Red Sea
2Gas GiantsHow are the gas giants similar?The four gas giants are thought to have small, dense cores and thick atmospheres that are mostly hydrogen and helium.
3Gas GiantsJupiter, Saturn, Uranus, and Neptune are very different from the terrestrial planets.They are much colder because of their distance from the sun.All four planets are much larger and more massive than the terrestrial planets.They are often referred to as the gas giants because they are composed mainly of hydrogen and helium.
4Gas GiantsNone of the gas giants have solid surfaces.If you tried to land a spaceship on one, you would sink into the planet until the intense pressure of the atmosphere crushed the ship.In fact, the pressure is so great inside each planet that hydrogen and helium exist mostly in liquid form.
5Gas GiantsGas giants have many moons, most of which revolve in the same direction that the planets rotate.Each of the gas giants is surrounded by rings. A ring is a disk made of many small particles of rock and ice in orbit around a planet.Rings are so close to the planet that gravitational forces are very large, which may have prevented the ring particles from clumping together to form moons.
6Gas GiantsThe outer planets consist of the four gas giants. Pluto, formerly considered a planet, was reclassified as a dwarf planet in 2006.
7JupiterWhat are the characteristics of Jupiter?Jupiter is the largest and most massive planet in our solar system.
8JupiterJupiter’s AtmosphereJupiter’s clouds move rapidly because Jupiter itself rotates rapidly—one day on Jupiter is less than 10 Earth hours.The brown cloud bands are colder and move faster around the planet than the white bands.
9JupiterSometimes storms occur at the boundaries between these brown and white bands.The Great Red Spot is a huge storm that rotates around its own center like a hurricane. It is caught between two bands of winds blowing in opposite directions.The Great Red Spot was first observed in 1664 but may be much older.
10JupiterThis model of Jupiter is based on photos taken by Voyager 1. The Great Red Spot, is a giant storm much larger than Earth.
11Jupiter has at least 63 moons. Jupiter’s MoonsJupiter has at least 63 moons.Most of them are small, less than 200 kilometers in diameter.Ganymede and Callisto are similar in size to Mercury.Io is covered with actively erupting volcanoes.Io and Europa are somewhat smaller, about the size of our moon.
12JupiterGanymede, Io, and Europa have metal cores and rocky mantles.Io is covered with actively erupting volcanoes.Ganymede, Europa, and Callisto are covered with ice.On Europa, the icy crust appears to rest on top of a liquid saltwater ocean. Scientists hypothesize that Europa is the most likely place in the solar system, other than Earth, to support life.
13JupiterIo is the most volcanically active body in the solar system. Io’s volcanic eruptions consist mainly of liquid sulfur.Europa may have a liquid water ocean beneath its icy surface. The dark lines are wide fractures in Europa’s crust.
14SaturnWhat are the characteristics of Saturn?Saturn’s rings are the largest and most visible from Earth.
15SaturnSaturn, the second largest planet in the solar system, is best known for its rings.The rings are made of particles of ice and ice-coated rock.These particles are generally between a few micrometers and 10 meters across, with most particles being snowball-sized.The rings are about 274,000 kilometers in diameter, yet are only tens of meters thick.
16SaturnSaturn’s AtmosphereLike Jupiter, Saturn has colorful banding in its atmosphere.Saturn’s atmosphere is the largest of any planet in the solar system. Saturn also has the lowest average density, less than the density of liquid water.Saturn’s atmosphere is made mostly of hydrogen and helium, with small amounts of other elements.
17SaturnSaturn has a thick atmosphere. It is surrounded by a spectacular set of rings, the largest in the solar system.
18Astronomers have found at least 56 moons orbiting Saturn. Saturn’s MoonsAstronomers have found at least 56 moons orbiting Saturn.Most of these moons are very small.Titan is larger than Mercury. Titan is the only planetary moon with a thick atmosphere.
19UranusWhat are the characteristics of Uranus?The axis of Uranus’s rotation is tilted more than 90°.
20UranusBecause Uranus is so far from the sun, it is very cold.Uranus’s atmosphere is mostly hydrogen and helium.It also has a large amount of methane, which gives the planet a distinct blue-green appearance.
21UranusStructure of UranusLike Jupiter and Saturn, Uranus has a dense core.This core is thought to be surrounded by a thick mantle layer of liquid water and dissolved ammonia.A layer of liquid hydrogen and helium surrounds the mantle.
22UranusUranus has rings, although they are not as visible as Saturn’s.Uranus has at least 27 moons, though most are quite small.
23UranusA Tilted PlanetThe most unusual characteristic of Uranus is that it lies nearly on its side.Uranus rotates in a direction opposite to the direction of its revolution around the sun. Uranus’s rings and moons revolve about the same tilted axis.
24UranusUranus’s northern and southern hemispheres alternate being exposed to the sun for many years, which causes immense storms.No one knows for sure why Uranus’s axis is so tilted.Scientists hypothesize that the tilt may have been caused by a collision with another large planetary body early in its history.
25UranusUranus is unusual in that its axis is tilted so that the planet rotates nearly on its side.
26NeptuneWhat are the characteristics of Neptune?Neptune’s bluish color comes from the methane in its atmosphere.
27NeptuneNeptune is so far from the sun that it takes a very long time—165 Earth years—for it to make one revolution.Neptune has about the same composition and is about the same size as Uranus.
28Neptune has clearly visible cloud patterns in its atmosphere. Thin, wispy clouds form high within Neptune’s atmosphere.Neptune’s clouds are made of methane ice crystals.Neptune also has large storms in its atmosphere.One storm, observed by the Voyager 2 space probe in 1989, was called the Great Dark Spot, but by 1994, the storm was gone.
29NeptuneThis photo of Neptune was taken by the Voyager 2 spacecraft. The Great Dark Spot, visible near the center, was similar in size to Earth.
30NeptuneNeptune has thin rings very similar to the rings of Uranus.In addition, Neptune has at least 13 moons. Triton, the only large moon, has a thin atmosphere and an icy surface.
31Dwarf PlanetsWhat is a dwarf planet?A dwarf planet, like a planet, is spherical and orbits the sun directly. But unlike a planet, a dwarf planet has not cleared the neighborhood around its orbit.
32Dwarf PlanetsIn 2006, astronomers established a new classification for certain objects in the solar system that share some, but not all, of the characteristics of a planet.Pluto, which for many years had been considered the ninth and most distant planet in the solar system, was reclassified as a dwarf planet.
33Dwarf PlanetsA dwarf planet is too small for its gravity to attract all the nearby debris, so dwarf planets tend to orbit in zones that contain many other objects.Pluto is much smaller than the inner or outer planets. Its diameter is about half that of Mercury.The density of Pluto is similar to that of Triton, suggesting a mixture of ice and rock.
34Dwarf PlanetsPluto’s orbit around the sun is more elliptical than those of the planets. Pluto actually swings closer to the sun at times than Neptune.Like Uranus, Pluto has a rotation axis that is tilted more than 90°.Pluto also has three moons, Charon, Nix, and Hydra.
35Dwarf PlanetsThe New Horizons space probe will reach the dwarf planet Pluto and its three moons in the year 2015.
36Dwarf PlanetsOther known dwarf planets include Eris and the asteroid Ceres.Many more solar system objects will likely be named dwarf planets once their shapes can be verified as being spherical.Not all astronomers agree on what defines a planet, and the classification of dwarf planet may be subjected to further debate.
37Comets and MeteoroidsWhat are comets and meteoroids?Comets are dusty pieces of ice and rock that partially vaporize when they pass near the sun. Meteoroids are pieces of rock, usually less than a few hundred meters in size, that travel through the solar system.
38Comets and MeteoroidsThere are many smaller objects moving through the inner solar system in two forms.Comets are dusty pieces of ice and rock that partially vaporize when they pass near the sun.Meteoroids are pieces of rock, usually less than a few hundred meters in size that travel through the solar system.
39Comets and MeteoroidsCertain ancient meteoroids have been largely unaltered since the birth of the solar system.These meteoroids are the oldest remnants of the early solar system.Scientists have used radioactive dating to determine their absolute age and have found that the solar system is about 4.6 billion years old.
40The Edge of the Solar System What lies in the outer solar system beyond Neptune?Most of the objects in the Kuiper belt lie in a doughnut-shaped region close to the ecliptic.Beyond the Kuiper belt lies a great reservoir of comets called the Oort cloud.
41The Edge of the Solar System Astronomers estimate that thousands of solar system objects exist beyond Neptune’s orbit.These objects are found largely in two regions, the Kuiper belt and the Oort cloud.The Kuiper belt extends from Neptune’s orbit out to about 100 AU or more from the sun.Pluto is an example of a Kuiper belt object.
42The Edge of the Solar System The solar system extends much farther out than the Kuiper belt.The Oort Cloud is a very sparse sphere of comets thought to encircle the solar system out to a distance of about 50,000 AU.Occasionally objects from the Oort cloud enter the inner solar system, where they appear as comets.
43The Edge of the Solar System Located in the outer reaches of the solar system, the Oort cloud is a sphere of comets surrounding the sun and planets.
44The planets referred to as the gas giants are composed mainly of Assessment QuestionsThe planets referred to as the gas giants are composed mainly ofnitrogen and oxygen.hydrogen and carbon dioxide.hydrogen and helium.carbon dioxide and fluorine.
45The planets referred to as the gas giants are composed mainly of Assessment QuestionsThe planets referred to as the gas giants are composed mainly ofnitrogen and oxygen.hydrogen and carbon dioxide.hydrogen and helium.carbon dioxide and fluorine. ANS: C
46The part of the solar system that is most distant from the sun is Assessment QuestionsThe part of the solar system that is most distant from the sun isNeptune.Pluto.the Kuiper belt.the Oort cloud.
47The part of the solar system that is most distant from the sun is Assessment QuestionsThe part of the solar system that is most distant from the sun isNeptune.Pluto.the Kuiper belt.the Oort cloud.ANS: D
48Assessment QuestionsMost meteroids consist primarily of ice and orbit the sun at a great distance in the Oort cloud or Kuiper belt. True False
49Assessment QuestionsMost meteroids consist primarily of ice and orbit the sun at a great distance in the Oort cloud or Kuiper belt. True FalseANS: F, comets