Overview of Our Solar System Overview of Our Solar System • Earth is one of nine planets revolving around, or orbiting, the Sun. • All the planets, as well as most of their moons, also called satellites, orbit the Sun in the same direction, and all their orbits, except Pluto’s, lie near the same plane. • The planets of our solar system have various sizes, surface conditions, and internal structures.
Overview of Our Solar System Early Ideas • Some aspects of planetary motion were difficult to explain and therefore... • In 1543, Copernicus suggested that the Sun was the center of the solar system, a heliocentric model. • Ancient astronomers assumed that the Sun, planets, and stars orbited a stationary Earth in what is now known as a geocentric model, meaning “Earth centered.”
Overview of Our Solar System Gravity and Orbits • The planets revolve around the sun due to its large gravitational force. • The planets move in an elliptical orbit, all in the same direction.
The Terrestrial Planets The Planets • The nine planets of our solar system can be grouped into two main categories according to their basic properties. • The terrestrial planets are the inner four planets of Mercury, Venus, Earth, and Mars that are close to the size of Earth and have solid, rocky surfaces. • The Jovian planets are the outer planets of Jupiter, Saturn, Uranus, and Neptune which are much larger, more gaseous, and lack solid surfaces. • Pluto, the ninth planet from the Sun, has a solid surface, but it does not fit into either category.
Categorizing Planets • Size is the major difference, but they also differ in density, chemical make-up and rate of rotation. • The terrestrial planets are smaller, denser, made of rocky and metallic substances and rotate slower. They also have less satellites, the most being two for Mars. • The Jovian (or outer) planets are larger, have a rig or rings, are less dense (Jupiter could float on water!) made of gasses and ice and have many satellites. Jupiter has 63 satellites!
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The Terrestrial Planets Mercury • Mercury is located closest to the Sun and has no moons. • Mercury is about one-third the size of Earth and has a smaller mass and radius. • A day is actually longer than a year on Mercury because of its very slow rotation. Mercury has a slow spin of 1407.6 hours so in two of Mercury’s years, three of Mercury’s days have passed.
The Terrestrial Planets Mercury Atmosphere • Mercury has essentially no atmosphere, and what little does exist is composed primarily of oxygen and sodium. • The daytime surface temperature on Mercury is 700 K (427ºC), while temperatures at night fall to 100 K (–173ºC). It is the largest temperature range.
The Terrestrial Planets Mercury Surface • Most of what we know about Mercury is based on radio observations and images from a United States space probe mission in 1974 & 5, called Mariner 10. • Mercury’s surface is covered with craters, making it look similar to the moon. • The plains are thought to have formed from lava flows, much like the moon.
The Terrestrial Planets Mercury Interior • The high density of Mercury suggests that it has an extensive nickel-iron core, filling about 42% of Mercury’s volume. • The detectable magnetic field suggests that Mercury has a molten zone in its interior. • Mercury’s small size, high density, and probable molten interior zone resemble what Earth might be like if its crust and mantle were removed. It’s possible these were lost in an early collision.
The Terrestrial Planets Venus • Venus, the second planet from the Sun, has no moons. • Venus’s high albedo and its proximity to Earth make it the brightest planet in Earth’s nighttime sky. • Venus rotates slowly counterclockwise with one day equaling 243 Earth days. • It has a retrograde rotation, meaning it rotates backwards from all the other planets. It may be due to an early collision.
The Terrestrial Planets Venus Surface • Venus was studied in 1978 by Pioneer-Venus and in 1989 the Magellan missions to map the surface of Venus in detail. • The surface has been smoothed by volcanic lava flows, and it has only a few impact craters. • The most recent global episode of volcanic activity took place about 500 million years ago. • There is little evidence of current tectonic activity on Venus, and there is no well-defined system of crustal plates.
The Terrestrial Planets Venus- our twin! • Venus is called “Earth’s Twin” because its size/diameter, mass and density are similar to Earth. Therefore, the internal structure is most likely similar.
Venus - temperature and pressure • Venus is the hottest planet in the solar system, hot enough to melt lead at 464°C! • The atmospheric pressure on Venus is 92 Earth atmospheres, compared to 1 on earth.
The Terrestrial Planets Venus Atmosphere • The atmosphere is made of CO2 and Na. Therefore it has an efficient greenhouse effect. The clouds will actually rain sulfuric acid. There are lots of clouds which leads to a “Runaway Greenhouse Effect” making it the hottest planet.
The Terrestrial Planets Earth • Earth, the third planet from the Sun, has many unique properties. • Its distance from the Sun and its nearly circular orbit allow liquid water to exist on its surface in all three states: solid, liquid, and gas. • Liquid water is required for life. • Earth’s moderately dense atmosphere (78 percent nitrogen and 21 percent oxygen) and a mild greenhouse effect support conditions suitable for life.
The Terrestrial Planets Mars • Mars is the fourth planet from the Sun. It is called the “Red Planet” because of iron oxide (rust) in the soil. • Mars is smaller and less dense than Earth. • It has two irregularly-shaped moons, Phobos and Deimos. They are captured asteroids.
Studying Mars • Missions include Mariner 4, Mariner 9, Mars Climate Orbiter and the Mars Explorer Rover Mission in 2003. • The rovers, Spirit and Opportunity are there still sending back information.
The Terrestrial Planets Mars Atmosphere • Atmosphere is made mostly of carbon dioxide. (similar to Venus) • The thin atmosphere is turbulent, which creates a constant wind on Mars. • Martian dust storms may last for weeks at a time.
The Terrestrial Planets Mars Surface • Mars has four gigantic shield volcanoes including Olympus Mons, the largest mountain in the solar system. • An enormous canyon, Valles Marineris, more than 4000km long, lies on the Martian equator and splits the Tharsis Plateau.
The Terrestrial Planets Mars Surface • Other surface features include dried river and lake beds and channel runoff. These suggest the existence of liquid water once on the surface of Mars. • Mars has ice caps of frozen carbon dioxide covering both poles that grow and shrink with the seasons on Mars. • Water ice lies beneath the carbon dioxide ice in the northern cap and we believer there might be liquid water under the surface of Mars.
The Terrestrial Planets Mars Interior • Astronomers are unsure about the internal structure of Mars. • It is thought to have a core of iron and nickel, and possibly sulfur which is covered by a mantle. • Because Mars has no magnetic field, the core is probably solid. • There is no evidence of current tectonic activity or tectonic plates on the surface of the crust.
The Gas Giant Planets The Gas Giant Planets • The interiors of the gas giant planets are composed of fluids, either gaseous or liquid, and possibly small, solid cores. • They are composed primarily of lightweight elements such as hydrogen, helium, carbon, nitrogen, and oxygen, and they are very cold at their surfaces. • The gas giants have many satellites as well as ring systems, and they are all very large.
The Gas Giant Planets Jupiter • Jupiter is 5th from the sun and is the largest planet. Its diameter is 11 times ours and only 10 times less than the sun. It makes up 70% of all matter in our solar system. • Jupiter has a banded appearance as a result of flow patterns in its atmosphere. • It has the Great Red Spot, a giant storm the size of Earth. • Jupiter has been explored by 5 U S space probes, Pioneer 10 and 11, Voyager I and II, and Spacecraft Galileo.
The Gas Giant Planets Jupiter Atmosphere • Jupiter has a low density, it could actually float on water! • Hydrogen and helium make up the majority of Jupiter’s atmospheric gas.
The Gas Giant Planets Jupiter Atmosphere • At less than 10 hours, Jupiter has the shortest day in the solar system.
The Gas Giant Planets Jupiter Moons and Rings • Has 63 moons, at last count. Jupiter’s four largest moons, Io, Europa, Ganymede, and Callisto, are called Galilean satellites. Three of these are larger than our moon and all are larger than Pluto! • There is volcanic activity on Jupiter’s closest major moon, Io. • Europa is believed to possibly have a subsurface ocean of liquid water. • Jupiter, like the other three gas giant planets, has rings.
The Gas Giant Planets Saturn • Saturn is the sixth planet from the Sun and the second-largest planet in the solar system. • In 2004, the United States Cassini mission, launched in 1997, become the fifth probe to visit the planet. The other missions were Pioneer 10 and 11 and Voyager I and II.
The Gas Giant Planets Saturn -- Like Jupiter, Saturn rotates rapidly for its size and has flowing belts. • Its density and structure are similar to Jupiter. Saturn has a small solid core with a large gaseous outside. • Saturn’s atmosphere is dominated by hydrogen and helium but it also includes ammonia ice. • Has magnetic field 1000 times Earth’s
The Gas Giant Planets Saturn Moo ns and Rings • Saturn’s ring system is the most striking, it has much broader and brighter rings than those of the other gas giant planets. • There are seven major rings composed of narrower rings, called ringlets, and many open gaps. • The ring particles are probably debris left over when a moon was destroyed either by a collision or Saturn’s gravity. They are made up of pieces of rock and ice, from microscopic bits up the size of houses.
The Gas Giant Planets Saturn Moons and Rings • It now has 31 known satellites • Titan is the largest, it is larger than Earth’s moon, and its atmosphere is made of nitrogen and methane. Methane may exist in three states there as water does on Earth
The Gas Giant Planets Uranus • The seventh planet from the Sun, Uranus, was discovered accidentally in 1781. • Two of Uranus’s larger moons, Titania and Oberon, were discovered in 1787. • Uranus has at least 18 moons and 10 rings. • In 1986, the United States Voyager 2 mission visited Uranus.
The Gas Giant Planets Uranus Atmosphere • Uranus is 4 times as large and 15 times as massive as Earth and has a blue, velvety appearance. • Uranus’s atmosphere is composed of helium and hydrogen and methane gas and has no distinct belts or zones. • Its internal structure is completely fluid except for a small, solid core and it has a strong magnetic field.
The Gas Giant Planets Uranus Atmosphere • The rotational axis of Uranus is tipped over so far that the north pole almost lies in its orbital plane. • Uranus’s atmosphere keeps the planet at a temperature of 58 K (–215°C).
The Gas Giant Planets Uranus Moons and Rings • The known moons and rings of Uranus orbit in the planet’s equatorial plane. • New moons are frequently being discovered causing frequent changes in the count. • Uranus’s rings are very dark—almost black.
The Gas Giant Planets Neptune • The existence of Neptune was predicted, based on small deviations in the motion of Uranus, before it was discovered. • In 1846, Neptune was discovered where astronomers had predicted it. • The Voyager 2 probe flew past Neptune in 1989.
The Gas Giant Planets Neptune Atmosphere • Neptune is slightly smaller and denser than Uranus, but it is still about four times as large as Earth. • Other similarities between Neptune and Uranus include their bluish color, atmospheric compositions, temperatures, magnetic fields, interiors, and particle belts. • Neptune does have distinctive clouds and atmospheric belts and zones similar to those of Jupiter and Saturn.
The Gas Giant Planets Neptune Moons and Rings • Neptune has many moons, the largest being Triton. • Triton has a retrograde orbit, which means that it orbits backward, unlike virtually every other large satellite in the solar system. • Triton also has a thin atmosphere and nitrogen geysers. • Neptune has six rings that are composed of microscopic-sized dust particles.
The Gas Giant Planets Pluto • Pluto, the ninth planet in our solar system, was discovered in 1930. • Pluto is very different from the other eight planets of our solar system and does not fit into either the terrestrial group or gas giant group. • The density of Pluto indicates that it is made of half ice and half rock, and it is smaller than Earth’s moon. • The atmosphere is composed of methane and nitrogen, but in unknown quantities.
The Gas Giant Planets Pluto • The orbit of Pluto is so eccentric that at aphelion, it is 50 AU from the Sun, and at perihelion, it is almost 30 AU from the Sun. • Pluto’s rotational axis is tipped so far over that its north pole actually points south of its orbital plane. • Pluto’s satellite, Charon, orbits in synchronous rotation at Pluto’s equatorial plane. • Many of Pluto’s properties are more similar to those of the gas giants’ large moons than they are to those of any other planet.
The Gas Giant Planets Section Assessment 1. What is liquid metallic hydrogen? Liquid metallic hydrogen is a form of hydrogen that has properties of both a liquid and a metal, which can exist only under conditions of very high pressure.
The Gas Giant Planets Section Assessment 2. Number the nine planets, starting with the closest to the Sun. ___ Uranus ___ Saturn ___ Mars ___ Pluto ___ Mercury ___ Neptune ___ Jupiter ___ Venus ___ Earth 7 6 4 9 1 8 2 5 3
The Gas Giant Planets Section Assessment 3. Identify whether the following statements are true or false. ______ Saturn’s rings are about 200 km thick. ______ Earth’s Moon is largest satellite in our solar system. ______ Jupiter’s Great Red Spot is a storm that has been ongoing for more than 300 years. ______ Jupiter makes up about 40 percent of all planetary matter in our solar system. false false true false
Formation of Our Solar System Objectives • Summarize the properties of the solar system that support the theory of the solar system’s formation. • Describe how the planets formed from a disk surrounding the young Sun. • Explore remnants of solar system formation. Vocabulary • planetesimal • asteroid • meteoroid • meteor • meteorite • comet • coma • nucleus • meteor shower
Formation of Our Solar System Formation of Our Solar System • Astronomers use Earth-based observations and data from probes to derive theories about how our solar system formed. • The significant observations related to our solar system’s formation include the shape of our solar system, the differences among the planets, and the oldest planetary surfaces, asteroids, meteorites, and comets.