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Chapter 28 Lecture Conceptual Integrated Science Second Edition The Solar System © 2013 Pearson Education, Inc. This lecture will help you understand: • • • • • • The Solar System and Its Formation The Sun The Inner Planets The Outer Planets Earth's Moon Failed Planet Formation © 2013 Pearson Education, Inc. The Solar System and Its Formation • The solar system consists of: – Sun – System of planets – Asteroids – Comets © 2013 Pearson Education, Inc. The Solar System and Its Formation • Planets are divided into two classes. – Inner planets: • • • • Mercury Venus Earth Mars – Outer planets: • • • • Jupiter Saturn Uranus Neptune © 2013 Pearson Education, Inc. The Solar System and Its Formation • According to the nebular theory, the Sun and planets formed together from a cloud of gas and dust—a nebula. © 2013 Pearson Education, Inc. The Solar System and Its Formation • Nebular theory formation – Gravitation between materials in the cloud pulled it inward. – When the cloud was pulled inward, its spin increased in accordance with the conservation of angular momentum. – The spinning cloud conformed to the shape of a spinning disk. © 2013 Pearson Education, Inc. The Solar System and Its Formation • Nebular theory formation (continued) – The center of the disk is the protosun. – Away from the center, planetesimals formed. – Planetesimals accreted more matter to become planets. © 2013 Pearson Education, Inc. The Solar System and Its Formation CHECK YOUR NEIGHBOR Which of the following orbits around the Sun? A. B. C. D. planets comets asteroids all of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. The Solar System and Its Formation CHECK YOUR NEIGHBOR As a nebula shrinks under the influence of gravity, it A. B. C. D. spins slower. spins faster. loses its spin. spins into a protosun. Explain your answer to your neighbor. © 2013 Pearson Education, Inc. The Sun • The Sun is the nearest star to Earth. • The Sun is composed of mostly hydrogen in the plasma phase. • Hydrogen is fused to helium by thermonuclear fusion in the Sun's core. • In the Sun 4.5 million tons of mass are converted to energy each second. • A tiny fraction of this energy reaches and sustains Earth. © 2013 Pearson Education, Inc. The Sun CHECK YOUR NEIGHBOR Strictly speaking, in every second that passes, the mass of the Sun A. B. C. D. decreases. remains constant. increases. reinvents itself. Explain your answer to your neighbor. © 2013 Pearson Education, Inc. The Inner Planets • The inner planets are the four nearest the Sun. They are composed of high-density solid rock. – Mercury – Venus – Earth – Mars • The orbital speeds of planets around the Sun decrease with increasing distance from the Sun. © 2013 Pearson Education, Inc. The Inner Planets • Mercury – Mercury is the closest planet to the Sun. – It is slightly larger than our Moon. – Mercury has almost no atmosphere because of its small size. – Mercury's daytime is long and hot (up to 430C); its nighttime is long and cold (about -170C). © 2013 Pearson Education, Inc. The Inner Planets • Venus – Venus is the next closest planet to the Sun. – Its diameter about 0.95 that of Earth. – Venus has a very dense atmosphere, made up of mostly carbon dioxide. – Venus is volcanically active and is a very harsh place. © 2013 Pearson Education, Inc. The Inner Planets • Earth – Earth is the third planet from the Sun—our home. – Earth is at a distance from the Sun where most of its water is neither solid nor gas, but liquid. © 2013 Pearson Education, Inc. The Inner Planets • Mars – Mars is the fourth planet from the Sun—a potential away-from-home habitat. – It is a little more than half Earth's size. – Mars has a thin atmosphere—95% carbon dioxide and 0.15% oxygen. – A planet with a thin atmosphere is ineffective in reducing the temperature difference between day and night! – On Mars, equatorial temperatures range from 30C during the day to –130C at night. – Mars is presently the focus of planetary exploration. © 2013 Pearson Education, Inc. The Inner Planets • Mars © 2013 Pearson Education, Inc. The Outer Planets • The outer planets are – gaseous, low-density worlds. – appreciably larger than Earth. – more widely spaced than the inner planets. – The outer planets in order of distance from the Sun: • • • • Jupiter Saturn Uranus Neptune © 2013 Pearson Education, Inc. The Outer Planets • Jupiter – Jupiter is the first of the outer planets, beyond Mars. – It is more than 11 times Earth's diameter—the giant of the solar system. – Jupiter's composition is more liquid than gaseous or solid. – Jupiter's atmospheric pressure is more than a million times that of Earth. © 2013 Pearson Education, Inc. The Outer Planets • Jupiter © 2013 Pearson Education, Inc. The Outer Planets • Jupiter (continued) – Jupiter's atmosphere is 82% hydrogen, 17% helium, and 1% methane, ammonia, and other molecules— cough! – There is no definite surface on Jupiter, as occurs on the inner rocky planets. – Jupiter's solid core is made up of iron, nickel, and other minerals. – Because of Jupiter's thick atmospheric blanket, its daytime and nighttime temperatures are about the same for equal altitudes above its "surface." © 2013 Pearson Education, Inc. The Outer Planets • Jupiter's four largest moons © 2013 Pearson Education, Inc. The Outer Planets • Jupiter's moon Europa has an ice-capped ocean, which may hold extraterrestrial life. © 2013 Pearson Education, Inc. The Outer Planets • Saturn – Saturn is most remarkable for its easily seen rings. – Saturn is twice as far from Earth as Jupiter is. – Saturn's diameter, excluding the rings, is about ten times that of Earth. – Saturn has the lowest density of all planets—it could float in a giant bathtub (density is less than that of water). © 2013 Pearson Education, Inc. The Outer Planets • Saturn (continued) – Saturn is surrounded by rings. • The rings are hypothesized to be bits of a moon never formed, or remnants of a moon torn apart by tidal forces. • The inner part of the rings, like any satellite, travels faster than the outer part of the ring system. • The rocks that make up the rings orbit independently of other rocks. © 2013 Pearson Education, Inc. The Outer Planets • Saturn's largest moon, Titan, was visited by the Cassini spacecraft. © 2013 Pearson Education, Inc. The Outer Planets • Uranus – Uranus is twice as far from Earth as Saturn is. – Uranus's diameter is about four times that of Earth. – Uranus is tilted 98 to the orbital plane—a most unusual feature. – Uranus has a faint ring system. – Uranus has a methane atmosphere and is a very cold place. © 2013 Pearson Education, Inc. The Outer Planets • Neptune – Neptune lies beyond Uranus. – Neptune's diameter is almost four times that of Earth, somewhat smaller than Uranus. – Its atmosphere is mainly hydrogen and helium. – Neptune has a highly elongated elliptical path about the Sun. © 2013 Pearson Education, Inc. The Outer Planets • Pluto – Since 2006, Pluto has been classified as a dwarf planet. – It is very unlike the other planets in composition, size, and orbit. – Pluto has a highly elliptical orbit, like comets. – It spends most of its orbital time well beyond Neptune, in the Kuiper belt. – Pluto's composition is like that of Kuiper belt objects. – Its look-alike neighbors are not classified as planets. – The former planetary status was more historical than astronomical. © 2013 Pearson Education, Inc. The Outer Planets CHECK YOUR NEIGHBOR Which planet is more dense than water? A. B. C. D. Mars Venus Neptune all of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. Earth's Moon • More is known about the Moon than any other celestial body. • The Moon's diameter is about one—quarter that of Earth. • The Moon has no atmosphere—no weather and erosion to conceal past scarring of its surface (wears no "makeup"). © 2013 Pearson Education, Inc. Earth's Moon • Twelve people have stood on the Moon. Here we see Buzz Aldrin, one of the three Apollo 11 astronauts. © 2013 Pearson Education, Inc. Earth's Moon © 2013 Pearson Education, Inc. Earth's Moon • Phases of the Moon © 2013 Pearson Education, Inc. Earth's Moon • The Moon spins about its polar axis as it revolves around Earth. © 2013 Pearson Education, Inc. Earth's Moon CHECK YOUR NEIGHBOR During the time of a new Moon, the A. B. C. D. Sun is between Earth and the Moon. Moon is between the Sun and Earth. Earth is between the Sun and the Moon. none of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. Earth's Moon CHECK YOUR NEIGHBOR During the time of a full Moon, the A. B. C. D. Sun is between Earth and the Moon. Moon is between the Sun and Earth. Earth is between the Sun and the Moon. none of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. Earth's Moon • A magnetic compass aligns with a magnetic field. • Like a compass in a magnetic field, the Moon aligns with Earth's gravitational field. © 2013 Pearson Education, Inc. Earth's Moon • Eclipses occur when the Moon's shadow falls on part of Earth. • This is a solar eclipse. © 2013 Pearson Education, Inc. Earth's Moon • A lunar eclipse occurs when Earth's shadow falls on the Moon. © 2013 Pearson Education, Inc. Earth's Moon • The red light of sunrises and sunsets all around Earth is refracted onto the Moon's surface during a lunar eclipse. © 2013 Pearson Education, Inc. Failed Planet Formation • Asteroids – Asteroids are small rocky bodies that orbit the Sun. – Most are located between Mars and Jupiter. – Some asteroids encounter Earth. – Unnoticed on the ground, asteroids are conspicuous on ice (the reason many are found in Antarctica). © 2013 Pearson Education, Inc. Failed Planet Formation • Comets – Comets differ from asteroids in chemical composition. – Comets are masses of water, methane, and ice—dirty snowballs. – Most are located in the Kuiper belt and Oort cloud. – Comets have highly elliptical (highly eccentric) orbital paths. – The tails of comets are swept outward from the Sun by solar wind. © 2013 Pearson Education, Inc. Failed Planet Formation © 2013 Pearson Education, Inc. Failed Planet Formation CHECK YOUR NEIGHBOR Asteroids are small rocky bodies that A. B. C. D. orbit the Sun. reside mainly between Mars and Jupiter. are smaller than Earth's Moon. all of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. Failed Planet Formation CHECK YOUR NEIGHBOR The tails of comets point in a direction A. B. C. D. toward the Sun. away from the Sun. at nearly right angles to the Sun. none of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc. Failed Planet Formation • Meteoroids are relatively small (sand-grain to boulder size) pieces of debris chipped off asteroids or comets. • A meteor is – a meteoroid that strikes Earth's atmosphere. – often called a "falling star." © 2013 Pearson Education, Inc. Failed Planet Formation • A meteorite is a meteoroid that survives the trip through the atmosphere and reaches Earth's surface. © 2013 Pearson Education, Inc. Failed Planet Formation CHECK YOUR NEIGHBOR Which of these makes contact with Earth's surface? A. B. C. D. meteor meteorite meteoroid none of the above Explain your answer to your neighbor. © 2013 Pearson Education, Inc.