Download Untitled

This Page
Left Blank
Intentionally
To Zara Hickman
Copyright © 2011 by Ron Miller
Seven Wonders beyond the Solar System
All rights reserved. International copyright secured. No part of this book may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means—electronic, mechanical, photocopying, recording, or otherwise—without the
prior written permission of Lerner Publishing Group, Inc., except for the inclusion of brief quotations in an acknowledged
review.
Twenty-First Century Books
A division of Lerner Publishing Group, Inc.
241 First Avenue North
Minneapolis, MN 55401 U.S.A.
Website address: www.lernerbooks.com
Library of Congress Cataloging-in-Publication Data
Miller, Ron, 1947Seven wonders beyond the solar system / by Ron Miller.
p. cm. — (Seven wonders)
Includes bibliographical references and index.
ISBN 978–0–7613–5454–3 (lib. bdg. : alk. paper)
1. Nebulae—Juvenile literature. 2. Extrasolar planets—Juvenile literature. 3. Solar system—Miscellanea—Juvenile
literature. I. Title.
QB855.2.M55 2011
523.8—dc22
2010028446
Manufactured in the United States of America
1 – DP – 12/31/10
2
eISBN: 978-0-7613-7278-3
Contents
Introduction —— 4
THE TARANTULA NEBULA —— 7
THE CRAB NEBULA —— 15
THE MYSTERIOUS PULSING STAR —— 25
THE BIGGEST KNOWN STAR —— 33
THE MOST EARTHLIKE
EXTRASOLAR PLANET —— 41
THE BIGGEST KNOWN GALAXY —— 53
THE SCULPTOR SUPERCLUSTER —— 63
The Tarantula Nebula
Timeline —— 70
Choose an Eighth Wonder —— 71
Glossary and Pronunciation Guide —— 72
Source Notes —— 74
Selected Bibliography —— 75
Further Reading and Websites —— 76
Index —— 78
3
INTRODUCTION
P
EOPLE LOVE TO MAKE LISTS OF THE BIGGEST
AND THE BEST. ALMOST TWENTY-FIVE HUNDRED YEARS AGO, A
WRITER NAMED
HERODOTUS
GREEK
MADE A LIST OF THE MOST AWESOME
THINGS EVER BUILT BY PEOPLE.
THE
LIST INCLUDED BUILDINGS,
STATUES, AND OTHER OBJECTS THAT WERE LARGE, WONDROUS, AND
IMPRESSIVE.
WRITERS
LATER,
OTHER WRITERS ADDED NEW ITEMS TO THE LIST.
EVENTUALLY AGREED ON A FINAL LIST. IT WAS CALLED THE
SEVEN WONDERS
OF THE
ANCIENT WORLD.
The list became so famous that people began imitating it. They made
other lists of wonders. They listed the Seven Wonders of the Modern
World and the Seven Wonders of the Middle Ages. People also made lists
of wonders of science and technology.
O UT
OF
THIS WORLD
But Earth isn’t the only place with wonders. Our planet shares the universe
with many other wondrous places. Earth is one of eight planets that orbit,
or circle, the Sun. The Sun and everything that circles it, including the
planets and their moons, make up a place called the solar system. Beyond
the solar system, the universe holds billions and billions of stars. These
stars are all suns, similar to the Sun. What worlds might circle them? What
wonders might they contain?
4
On a cloudless night, far from city lights, you can see countless stars in the sky. Each of these stars is a sun,
similar to our Sun.
BEYOND
THE
SOLAR SYSTEM
Seven Wonders beyond the Solar System will take you on an amazing journey
to faraway places. On this journey, we’ll learn about stars that are being
born and stars that have already died. We’ll explore very tiny stars, as well as
stars as big as our whole solar system. We’ll learn how astronomers, or space
scientists, look for new stars and planets. We’ll even join astronomers as they
search for life on other planets. We’ll also examine giant clusters of stars
called galaxies. We’ll learn how galaxies cluster together to create the biggest
thing there is—the universe itself. Read on to visit this fascinating world
billions of miles away in space.
5
temperature. It takes 10 million years of contraction for a nebula to reach the
temperature needed for fusion to begin. As soon as the spark of fusion is lit,
the nebula stops contracting. It becomes a full-ledged sun. It begins running on
the energy produced by fusion. A star has been born.
THE BIGGEST STAR FACTORY
If you live in the Southern Hemisphere (southern half of Earth), you can look
into the sky at night and see the Tarantula Nebula. It is the largest “star nursery”
anyone knows about. Hundreds and perhaps even thousands of new stars are
being born within it.
Seven Wonders beyond the Solar System
Powerful telescopes in the Southern Hemisphere allow us to see the young stars inside the
Tarantula Nebula.
10
The nebula looks a little like a tarantula, a big hairy spider.
The Tarantula Nebula
To the naked eye, the Tarantula Nebula doesn’t look like much. It looks like
a faint, fuzzy blob of light in the constellation (star group) Dorado. When seen
through a telescope, however, the Tarantula Nebula looks like a swirling mass
of red and green gases. Its shape resembles a tarantula, a large hairy spider.
A light-year is the distance light travels in one year. Light travels 186,000
miles (300,000 kilometers) per second. So 1 light-year equals about 5.88
trillion miles (9.46 trillion km). The Tarantula Nebula is 170,000 light-years
away from Earth. So light from the Tarantula Nebula takes 170,000 years to
reach Earth.
At the center of the Tarantula Nebula is a small cluster of young stars.
Energy from these stars makes the nebula glow brightly, much like electricity
passing through the tube of a neon sign makes the gas inside it glow.
11
Seven Wonders beyond the Solar System
12
The Hubble Space Telescope, which orbits Earth, took this picture of the Orion Nebula in Orion’s
sword (see illustration on page 27). The nebula contains more than three thousand stars.
Sometimes a very large star explodes. When it does, it bursts into a
supernova. In this titanic explosion, the star suddenly lares with a billion
times the brightness of the Sun. At the same time, the star’s atmosphere, or
surrounding layer of gases, blasts out into space. The explosion looks like a
beautiful shell of glowing gas. For a few days, the supernova outshines the
combined stars of its entire galaxy.
BANG !
Scientists aren’t entirely sure what causes a star to explode. But they do know
about two types of supernovas. One type of supernova requires two stars that
Seven Wonders beyond the Solar System
This painting shows what a supernova would look like if viewed from Earth’s Moon.
16
A white dwarf can be as massive (have as much mass) as the Sun. With
so much mass crammed into such a small space, white dwarfs are very dense.
Denser objects have more gravity than objects with less density.
When a white dwarf and a larger star orbit each other, the white dwarf’s
powerful gravity pulls on the larger star. Gases from the big star low to the
white dwarf. Eventually, too much mass builds up on the white dwarf. The
excess mass causes the white dwarf to blow up. The entire star suddenly
disappears in a single, incredible explosion.
A star that has too much mass to remain stable, or unchanging, can lead
to the second type of supernova. Such a star is typically more than six times
as massive as the Sun. When the massive star gets old and runs out of gaseous
fuel to burn, it collapses. This collapse creates tremendous pressure in the core
of the star. This pressure can trigger violent fusion reactions. They can cause
the star to explode into a supernova. After a supernova, only the tiny core of
the star remains.
Seven Wonders beyond the Solar System
THE GHOSTS
18
OF
STARS
The night sky is illed with the remains of supernovas. They are colorful clouds
of dust and gas left over from the explosions. No two are exactly alike. One
of the most beautiful such clouds is the Crab Nebula. Through a telescope, it
looks like a lacy burst of multicolored strands.
The Crab Nebula is the result of a star that was seen to explode in the year
1054. It actually exploded sixty-ive hundred years earlier. But the Crab Nebula
is 6,500 light-years from Earth. So it took light from the explosion sixty-ive
hundred years to reach Earth.
In July of 1054, Chinese astronomers noted the appearance of a “guest
star” (a temporary star) in the constellation Taurus. People could see the guest
star in broad daylight for three weeks. They saw it at night for two years before
it inally faded away. The Chinese astronomers didn’t know it, but they had
witnessed the supernova that created the Crab Nebula.
Native Americans in Chaco Canyon in New Mexico may also have
witnessed this impressive sight. A pictograph (rock painting) there appears to
show a new star. It is shown near a crescent moon. The crescent moon would
have appeared in the sky very close to the supernova in July 1054.