Astronomy Book PDF - Cosmic Perspective

BENNETT DONAHUE SCHNEIDER VOIT COSMIC THE PERSPECTIVE E I GHTH ED ITI O N  You Are Here in Space One of the best reasons to study modern astronomy is to learn about your place in...

BENNETT DONAHUE SCHNEIDER VOIT COSMIC THE PERSPECTIVE E I GHTH ED ITI O N  You Are Here in Space One of the best reasons to study modern astronomy is to learn about your place in the universe. This visual will lead you through the basic levels of structure, starting with the universe as a whole and ending with Earth. The Observable Universe The Local Group The Milky Way Galaxy The Nearest Stars The Solar System The Earth–Moon System Earth The background illustration depicts the overall This image shows the largest galaxies in our Local Group. Most galaxies are members of small groups of This illustration shows what the Milky Way Galaxy would look like from the outside. Our This image shows the locations of nearby stars; stars would be atom-sized on this This diagram shows the orbits of the planets around the Sun; the planets This diagram shows Earth, the Moon, and the Moon’s orbit to scale. You are here. The physical sizes of human beings and even the distribution of galaxies in our observable universe; up to a few dozen galaxies, such as our own Local Group, or larger clusters containing up to a few thousand galaxy is one of the three largest members of the Local Group. The Milky Way contains more than scale, so their sizes have been greatly exaggerated for visibility. Zooming in on a tiny themselves are microscopic on this scale. Our solar system consists of the Sun We must magnify the image of our solar system another 10,000 times to planet on which we live are almost unimaginably small compared individual galaxies are microscopic on this scale. The galaxies. 100 billion stars — so many stars that it would take thousands of years just to count them out loud. piece of the Milky Way brings us to the nearby stars of our local solar neighborhood. While and all the objects that orbit it, including the planets and their moons, and countless get a clear view of our home planet and its constant companion, our Moon. to the vastness of space. Yet in spite of this fact, we have managed portion of the universe that we can observe is limited by the we see only stars, we now know that many (perhaps most) stars are orbited by planets. smaller objects such as asteroids and comets. to measure the size of the observable universe and to discover age of the universe: Because our universe is about 14 billion 4 million light-years ≈ 4 x 1019 km how our lives are related to the stars. years old, we can see no more than about 14 billion light-years in any direction. Measurements indicate that the 2 million light-ye ars observable universe contains more than 100 billion galaxies. 100,000 light-years ≈ 1018 km 1 million ly 50,000 li gh t-year 1 billion light-years s 24 light-years ≈ 2 x 1014 km 30,000 ly 12 light-year 0 s On the largest scales, galaxies are arranged in giant 10 60 AU ≈ 1010 km chains and sheets millions of light years long. r≈ cto 6 ly fa om zo 40 800,000 km actor ≈ zoom f 00 ≈ 40 13,000 km Milky Way tor fac Large Magellanic Cloud zoo m 000 Small Magellanic Cloud ≈ 20, tor BINDING EDGE ac 61 Cygni mf 000 zoo Even the Moon’s orbit around Earth 10, is far too small to see on this scale. ≈ 40 tor fac tor ≈ oom m fac z Andromeda Procyon A, B zoo (M31) Sun Sirius A, B Earth Even the smallest dot in this image covers a The location of our solar system is about region containing millions of stars. 27,000 light-years from the galactic center. Proxima Centauri  Centauri A, B  Eridani Uran Ross 154 Nep us’s orbit Moon Triangulum (M33) tune ’s orbi t Our Sun is a star, just like the many stars we  Ceti see in the night sky. The Moon is the only world besides Earth upon which humans have ever stepped. Putting Space in Perspective The Voyage scale model solar system in Washington, D.C. uses this 1-to-10 billion scale, making it possible to walk to the outermost planets in just a few On the 1-to-10 billion scale, you’d have to cross the United States to reach the nearest stars. A water molecule is a million times smaller than a grain of sand. On the 1-to-10 billion These comparisons show how tiny we are compared to the solar system in which we live, minutes. scale, you would be slightly smaller than a but we’ve only just begun to cover the range of One good way to put the vast sizes and distances of astronomical objects into water molecule. scales in the universe. perspective is with a scale model. In this book, we’ll build perspective using a model Mars To appreciate the size of our galaxy, that shows our solar system at one-ten-billionth its actual size. Venus consider that the stars on this scale are like Pluto Neptune Uranus Saturn Jupiter grapefruits thousands of kilometers apart, SUN  Centauri yet there are so many that it would take you Sun thousands of years to count them On the 1-to-10 billion scale, Earth is only about the On the 1-to-10 billion scale, the distance from to Washington Monument Mercury one-by-one. size of a ballpoint in a pen (1 millimeter across). the Sun to the Earth is about 15 meters. Earth And with more than 100 billion galaxies, the observable universe contains a total number Art and Industries of stars comparable to the number of grains Hirshhorn National Air and Space Museum Building Museum of dry sand on all the beaches on Earth combined. This photo of the Hubble Ultra Deep Field shows On the 1-to-10 billion scale, the Sun is about the This map shows planet locations in the Voyage model. Keep in mind that One light-year becomes 1000 kilometers on the Voyage scale, so even the nearest stars are galaxies visible in a patch of sky that you could size of a large grapefruit (14 centimeters across). planets actually follow orbits that go all the way around the Sun. more than 4000 kilometers away, equivalent to the distance across the United States. cover with a grain of sand held at arm’s length.  You Are Here in Space One of the best reasons to study modern astronomy is to learn about your place in the universe. This visual will lead you through the basic levels of structure, starting with the universe as a whole and ending with Earth. The Observable Universe The Local Group The Milky Way Galaxy The Nearest Stars The Solar System The Earth–Moon System Earth The background illustration depicts the overall This image shows the largest galaxies in our Local Group. Most galaxies are members of small groups of This illustration shows what the Milky Way Galaxy would look like from the outside. Our This image shows the locations of nearby stars; stars would be atom-sized on this This diagram shows the orbits of the planets around the Sun; the planets This diagram shows Earth, the Moon, and the Moon’s orbit to scale. You are here. The physical sizes of human beings and even the distribution of galaxies in our observable universe; up to a few dozen galaxies, such as our own Local Group, or larger clusters containing up to a few thousand galaxy is one of the three largest members of the Local Group. The Milky Way contains more than scale, so their sizes have been greatly exaggerated for visibility. Zooming in on a tiny themselves are microscopic on this scale. Our solar system consists of the Sun We must magnify the image of our solar system another 10,000 times to planet on which we live are almost unimaginably small compared individual galaxies are microscopic on this scale. The galaxies. 100 billion stars — so many stars that it would take thousands of years just to count them out loud. piece of the Milky Way brings us to the nearby stars of our local solar neighborhood. While and all the objects that orbit it, including the planets and their moons, and countless get a clear view of our home planet and its constant companion, our Moon. to the vastness of space. Yet in spite of this fact, we have managed portion of the universe that we can observe is limited by the we see only stars, we now know that many (perhaps most) stars are orbited by planets. smaller objects such as asteroids and comets. to measure the size of the observable universe and to discover age of the universe: Because our universe is about 14 billion 4 million light-years ≈ 4 x 1019 km how our lives are related to the stars. years old, we can see no more than about 14 billion light-years in any direction. Measurements indicate that the 2 million light-ye ars observable universe contains more than 100 billion galaxies. 100,000 light-years ≈ 1018 km 1 million ly 50,000 li gh t-year 1 billion light-years s 24 light-years ≈ 2 x 1014 km 30,000 ly 12 light-year 0 s On the largest scales, galaxies are arranged in giant 10 60 AU ≈ 1010 km chains and sheets millions of light years long. r≈ cto 6 ly fa om zo 40 800,000 km actor ≈ zoom f 00 ≈ 40 13,000 km Milky Way tor fac Large Magellanic Cloud zoo m 000 Small Magellanic Cloud ≈ 20, tor BINDING EDGE ac 61 Cygni mf 000 zoo Even the Moon’s orbit around Earth 10, is far too small to see on this scale. ≈ 40 tor fac tor ≈ oom m fac z Andromeda Procyon A, B zoo (M31) Sun Sirius A, B Earth Even the smallest dot in this image covers a The location of our solar system is about region containing millions of stars. 27,000 light-years from the galactic center. Proxima Centauri  Centauri A, B  Eridani Uran Ross 154 Nep us’s orbit Moon Triangulum (M33) tune ’s orbi t Our Sun is a star, just like the many stars we  Ceti see in the night sky. The Moon is the only world besides Earth upon which humans have ever stepped. Putting Space in Perspective The Voyage scale model solar system in Washington, D.C. uses this 1-to-10 billion scale, making it possible to walk to the outermost planets in just a few On the 1-to-10 billion scale, you’d have to cross the United States to reach the nearest stars. A water molecule is a million times smaller than a grain of sand. On the 1-to-10 billion These comparisons show how tiny we are compared to the solar system in which we live, minutes. scale, you would be slightly smaller than a but we’ve only just begun to cover the range of One good way to put the vast sizes and distances of astronomical objects into water molecule. scales in the universe. perspective is with a scale model. In this book, we’ll build perspective using a model Mars To appreciate the size of our galaxy, that shows our solar system at one-ten-billionth its actual size. Venus consider that the stars on this scale are like Pluto Neptune Uranus Saturn Jupiter grapefruits thousands of kilometers apart, SUN  Centauri yet there are so many that it would take you Sun thousands of years to count them On the 1-to-10 billion scale, Earth is only about the On the 1-to-10 billion scale, the distance from to Washington Monument Mercury one-by-one. size of a ballpoint in a pen (1 millimeter across). the Sun to the Earth is about 15 meters. Earth And with more than 100 billion galaxies, the observable universe contains a total number Art and Industries of stars comparable to the number of grains Hirshhorn National Air and Space Museum Building Museum of dry sand on all the beaches on Earth combined. This photo of the Hubble Ultra Deep Field shows On the 1-to-10 billion scale, the Sun is about the This map shows planet locations in the Voyage model. Keep in mind that One light-year becomes 1000 kilometers on the Voyage scale, so even the nearest stars are galaxies visible in a patch of sky that you could size of a large grapefruit (14 centimeters across). planets actually follow orbits that go all the way around the Sun. more than 4000 kilometers away, equivalent to the distance across the United States. cover with a grain of sand held at arm’s length.  You Are Here in Space One of the best reasons to study modern astronomy is to learn about your place in the universe. This visual will lead you through the basic levels of structure, starting with the universe as a whole and ending with Earth. The Observable Universe The Local Group The Milky Way Galaxy The Nearest Stars The Solar System The Earth–Moon System Earth The background illustration depicts the overall This image shows the largest galaxies in our Local Group. Most galaxies are members of small groups of This illustration shows what the Milky Way Galaxy would look like from the outside. Our This image shows the locations of nearby stars; stars would be atom-sized on this This diagram shows the orbits of the planets around the Sun; the planets This diagram shows Earth, the Moon, and the Moon’s orbit to scale. You are here. The physical sizes of human beings and even the distribution of galaxies in our observable universe; up to a few dozen galaxies, such as our own Local Group, or larger clusters containing up to a few thousand galaxy is one of the three largest members of the Local Group. The Milky Way contains more than scale, so their sizes have been greatly exaggerated for visibility. Zooming in on a tiny themselves are microscopic on this scale. Our solar system consists of the Sun We must magnify the image of our solar system another 10,000 times to planet on which we live are almost unimaginably small compared individual galaxies are microscopic on this scale. The galaxies. 100 billion stars — so many stars that it would take thousands of years just to count them out loud. piece of the Milky Way brings us to the nearby stars of our local solar neighborhood. While and all the objects that orbit it, including the planets and their moons, and countless get a clear view of our home planet and its constant companion, our Moon. to the vastness of space. Yet in spite of this fact, we have managed portion of the universe that we can observe is limited by the we see only stars, we now know that many (perhaps most) stars are orbited by planets. smaller objects such as asteroids and comets. to measure the size of the observable universe and to discover age of the universe: Because our universe is about 14 billion 4 million light-years ≈ 4 x 1019 km how our lives are related to the stars. years old, we can see no more than about 14 billion light-years in any direction. Measurements indicate that the 2 million light-ye ars observable universe contains more than 100 billion galaxies. 100,000 light-years ≈ 1018 km 1 million ly 50,000 li gh t-year 1 billion light-years s 24 light-years ≈ 2 x 1014 km 30,000 ly 12 light-year 0 s On the largest scales, galaxies are arranged in giant 10 60 AU ≈ 1010 km chains and sheets millions of light years long. r≈ cto 6 ly fa om zo 40 800,000 km actor ≈ zoom f 00 ≈ 40 13,000 km Milky Way tor fac Large Magellanic Cloud zoo m