The Magnetic Universe

Contents

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Preface

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pp. vii-ix

Imagine that Federal Express delivers a package to you. There is no return address on the package, so you open it warily. Inside, you find a pair of dark eyeglasses. You put them on, and immediately you are in total darkness. But as your eyes adapt, you see that you are immersed in a thicket of shimmering threads. Everywhere you turn you see them. As you turn and move about the ...

1. GETTING REACQUAINTED WITH MAGNETISM

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pp. 1-8

Nowadays, a child first encounters magnetism in school while handling a permanent magnet. She sprinkles iron filings on a paper held over the magnet and smiles at the lovely pattern she’s created (fig. 1.1). She’s taught that these are “lines of force,” and she can see that they connect the “poles” of the magnet. With two magnets in hand, she can actually feel the force of repulsion...

2. THE EARTH

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pp. 9-30

On the night of March 6, 1716, Astronomer Royal Sir Edmund Halley was awakened by the noise of a great crowd outside his London home. People in the street were cheering and pointing at the sky. He dressed quickly and stepped into his garden. When he looked up, he was thunderstruck. A luminous cloud, with shimmering rays of yellow, red, and green, stretched from ...

3. SUNSPOTS AND THE SOLAR CYCLE

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pp. 31-58

Anyone who has seen recent images of the Sun (fig. 3.1) obtained by such satellites as the Solar and Heliospheric Observatory (SOHO) and the Transition Region and Coronal Explorer (TRACE) can’t help being impressed. Far from being the boring round ball one sees at sunset, the Sun is festooned with intricate decorations. Its surface is covered with a forest of x-ray loops ...

4. THE VIOLENT SUN

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pp. 59-83

On the night of December 12, 2006, two astronauts, African American Robert Curbeam and a Swede, Christer Fuglesang, were installing a 2-ton truss between solar panels on the International Space Station. Suddenly they were told to scramble back on board the Space Shuttle Discovery just as fast as possible. A large solar flare had erupted just minutes before, and a blast of ...

5. THE HELIOSPHERE: WINDS, WAVES, AND FIELDS

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pp. 84-112

As we go about our daily routines on a sunny, spring-like day, we’re blissfully unaware of the storm that rages just outside the Earth’s atmosphere. A supersonic wind of plasma blows off the Sun in all directions, past the Earth and beyond Pluto. The wind is strong enough to sweep back the Earth’s magnetic field, like the streaming hair of a girl on a....

6. THE EARTH’S MAGNETOSPHERE AND SPACE WEATHER

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pp. 113-140

At 9:07 in the evening of October 30, 2003, the entire electric power grid of southern Sweden shut down. Malm�, a city of 250,000, went dark in the blink of an eye, as though a giant hand had pulled the plug. Traffic signals all over the city snapped off , and hospitals went on emergency power. The city waited several hours for electricity to be...

7. THE PLANETS

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pp. 141-173

Four and a half billion years ago, the Sun and its family of planets were born from a giant cloud of interstellar gases. As scientists reconstruct the event, the slowly spinning cloud collapsed under its own gravity and spun up to form a flat disk. Most of the mass collected at the center, in a warming protostar that would become the Sun. Clumps of frozen gases in the disk drew ...

8. MAGNETIC FIELDS AND THE BIRTH OF STARS

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pp. 174-197

In 1995, the Hubble Space Telescope captured intimate views of several stars in the throes of birth (fig. 8.1). In the top two panels, we see young stellar objects, each surrounded by a flat rotating disk and each ejecting a jet that stretches for billions of kilometers. Hundreds of such objects are forming at this moment in the Orion Nebula and others like it in the....

9. ABNORMAL STARS

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pp. 198-211

Back around 1896, Annie Jump Cannon was one of a group of women working for Dr. Edward Pickering, director of the Harvard College Observatory. He had them sorting stars according to their spectral characteristics, with the aim of compiling a comprehensive catalog. The catalog would be dedicated to the memory of Henry Draper, a prominent New York doctor ...

10. COMPACT OBJECTS

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pp. 212-243

On the night of January 31, 1862, Alvan Graham Clark was testing a newly finished telescope at the Dearborn Observatory in Evanston, Illinois. He and his father, Alvan Clark, were famous Boston opticians who had fabricated the lens of the telescope. To test the lens, they were looking at close double stars to see whether they could resolve...

11. THE GALAXIES

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pp. 244-264

In the mid-eighteenth century, astronomers like Charles Messier were finding faint blurry “nebulae” all over the sky. Messier considered them a nuisance, because his prime interest was finding new comets and the nebulas distracted him. He decided to compile a catalog of them so as to avoid them in the future. On the night of October 13, 1773, he spied yet another, in the ...

12. SOMETHING FROM NOTHING: SEED FIELDS

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pp. 265-280

We come at last to the vexing question of how the first magnetic fields in the universe arose. We’ve seen how magnetic fields can be amplified in many different astrophysical situations. Gravitational collapse is a prime mechanism. As a protostar forms from the interstellar gas; as a galaxy forms from the intergalactic medium; as a white dwarf or a neutron star shrinks to its ...

Notes

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pp. 281-290

Index

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pp. 291-296