by Lucie Green
Wittmann, A. D. and Xu, Z. T., ‘A catalogue of sunspot observations from 165 BC to AD 1684’, Astronomy and Astrophysics Supplement Series, vol. 70, no. 1 (1987), 83–94
Wollaston, W. H., ‘A method of examining refractive and dispersive powers, by prismatic reflection’, Phil. Trans. R. Soc. Lond., vol. 92 (1802), 365–80
Zeeman, P., ‘On the influence of magnetism on the nature of the light emitted by a substance’, Astrophysical Journal, vol. 5 (1897), 332
Zhitnik, I. A., et al., ‘Observations of the Sun and its spectrum at 9.5–200 A’, Cosmic Research, vol. 5, 237
BOOKS
Eddington, A. S., The Internal Constitution of the Stars, Cambridge University Press, 1926
Foukal, P. V., Solar Astrophysics, Wiley-VCH, 2013
Hale, G. E. and Nicholson, S. B., Magnetic Observations of Sunspots, Carnegie Institution of Washington, 1938
Howard, T., Coronal Mass Ejections: An Introduction, Springer, 2011
Massey, H. S. W. and Robins, M. O., History of British Space Science, Cambridge University Press, 1986
Payne, C. H., Stellar Atmospheres: A Contribution to the Observational Study of High Temperature in the Reversing Layers of Stars, Harvard Observatory, 1925
Phillips, K. J. H., Guide to the Sun, Cambridge University Press, 1992
Schrijver, C. J. and Zwaan, C., Solar and Stellar Magnetic Activity, Cambridge University Press, 2008
Stix, M., The Sun: An Introduction, Springer, 2002
Tayler, R. J., The Sun as a Star, Cambridge University Press, 1996
Glossary
convection zone Region in which energy is transferred mostly by the convection motions of the plasma located between the radiation zone and the photosphere
corona Outermost atmosphere of the Sun seen in visible light during a total solar eclipse and in X-ray and extreme ultraviolet images from space
coronal mass ejection A sudden eruption of magnetic field and plasma from the Sun’s atmosphere into the Solar System
electron A negatively charged subatomic particle
flux rope A bundle of twisted magnetic field lines and electric currents
helioseismology The study of the solar interior using sound waves observed in the photosphere
heliosphere The magnetic and plasma bubble created by the outflowing solar wind and encompassing the Solar System
ion Positively charged particle formed from an atom that isn’t electrically balanced
light year The distance that light travels during one year – 9.46 million million kilometres. Often used as a unit of distance in astronomy
magnetic helicity A quantity that describes how twisted, linked and distorted a magnetic field is
magnetosphere The region of space surrounding an astronomical body which is filled by the object’s magnetic field
nuclear fusion A nuclear reaction in which light atomic nuclei fuse together to form a heavier nucleus, releasing energy in the process
nucleus The central part of an atom or ion that contains protons and neutrons
photosphere The ‘visible’ surface of the Sun and the deepest layer that we can see in visible light
plasma A gas consisting of separated electrically charged particles (electrons and ions) in roughly equal propotions so that there is no overall charge
poloidal A magnetic field which has field lines that are parallel to lines of longitude
radiation zone Region in which energy is transferred mostly by photons located between the core and the convection zone
refraction Change in direction of a wave caused by different parts of the front of the wave moving at different speeds
solar dynamo A collection of processes that produce a varying magnetic field in a star. A dynamo involves the conversion of kinetic energy in the gas motions into magnetic energy
solar flare A sudden burst of electromagnetic radiation in the atmosphere of the Sun. The glow can last from minutes to hours and has a strong X-ray component
solar limb Edge of the disc of the Sun
solar nebula The cloud of gas and dust from which the Sun and the other Solar System bodies formed
spectroheliograph An instrument that creates an image of the Sun in one wavelength only
spectrum The entire range of wavelengths of light emitted or absorbed by a substance
sunspot Relatively dark and cool region in the photosphere that is created by an intense magnetic field
tachocline Region between the rigidly rotating radiation zone and the convection zone where rotation changes with latitude and depth
toroidal Having the shape of a torus
Acknowledgements
Right from the start I had support from Sarah Green, Ben Dixon, Valerie Green, Alan Green, Julia Green, Simon Green, Anna Wu and Mike Wu, who all gave great advice on how to turn an academic subject into a human story. And my husband, Matt Parker, gets special thanks for the constant supply of tea and patience.
I would like to thank the following colleagues who have read and commented on sections of the book at various points along the way: Mitch Berger, Dave Brooks, Paul Cannon, Bill Chaplin, Paul Crowther, Len Culhane, Pascal Démoulin, Lidia van Driel-Gesztelyi, Peter Gallagher, Joanna Haigh, Hugh Hudson, Bernhard Kliem, Mike Lockwood, Andrew Richards, Sami Solanki, Kinwah Wu and my enthusiastic Ph.D. student Stephanie Yardley. Len Culhane, who was my Ph.D. supervisor, has always been kind enough to answer all my questions about the origin of the UK and European space programmes as well as the history of the Mullard Space Science Laboratory, sharing his recollections of the rapid pace of discovery and international collaborations. And I would like to thank George Doschek, who shared with me his stories about the research carried out with Skylab. When it comes to space weather, Doug Biesecker has for many years been a source of inspiration and has shared with me the history of space weather monitoring in the US. Then there is Lewis Dartnell, who gave me insight into the effects of radiation on the human body. And much of the research around the Thames freezing over in 1814 was done with the team I worked with on the Killer Storms and Cruel Winters programme for BBC4.
So many of the stories on these pages have been shared amongst members of the solar physics community, both in the UK and abroad. And the stories I didn’t have space to tell would fill many more books. It was painful having to leave so many important and interesting ones out. But I hope I have captured some old favourites here, and also some new stories too. I owe a lot to the solar and astrophysics community, who have always been keen to discuss the science and the history of our research area. In particular, my group at UCL gets a special mention, including past members Bernhard Kliem and Tibor Török, who taught me so much about the physics of magnetic fields and numerical modelling of coronal mass ejections. Then, there are three very special people whom I caught the solar physics bug from in the first place through their infectious enthusiasm, curiosity and support: Lidia van Driel-Gesztelyi, Pascal Démoulin and Cristina Mandrini. Thank you.
The wider community also includes the instrument teams who built such successful telescopes and who are now building the solar satellites of the future. They work behind the scenes but deserve huge recognition for their innovation and ability to overcome the challenges pres
ented by placing telescopes in space.
The process of writing this book, despite knowing the subject area, was lengthy. So I want to say a huge thank you to my two editors: Will Hammond, who got me off the blocks, and Daniel Crewe, who saw me across the finishing line. Together they taught me how to take facts and figures and weave them into a narrative that is colourful and meaningful.
Various people helped with the images that are a necessary part of such a visual subject, including Sian Prosser at the Royal Astronomical Society and John Grula, Cindy Hunt and Dan Kohne of the Carnegie Observatories. I also would like to thank the Leverhulme Trust and the Royal Society, which have supported my research through Fellowship schemes during this time.
THE BEGINNING
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Penguin Books is part of the Penguin Random House group of companies whose addresses can be found at global.penguinrandomhouse.com.
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First published 2016
Copyright © Lucie Green, 2016
The moral right of the author has been asserted
ISBN: 978-0-241-96356-2
1. LIGHT: DON’T BELIEVE YOUR EYES
* In 2012, the International Astronomical Union, the official body responsible for approving distance units in astronomy, defined the Astronomical Unit, the distance between the Sun and the Earth, to be 149,597,870,700 metres.
2. STAR POWER
* In fact, William Herschel proposed that the Sun’s output could be measured and made an attempt himself to do this qualitatively by looking at variations in solar output by studying how the price of wheat varied. He reasoned that when the Sun’s output was low, crops would be less abundant and the price of wheat would go up!
* Although there is some evidence that other scientists were close to realizing this equation, e.g. Friedrich Hasenöhrl.
* Necessarily, then, steps one and two must be completed twice for there to be sufficient particles for step three to take place.
4. THE SECRET LIFE OF A PHOTON
* The visible spectrum of light from hydrogen contains spectral lines at four wavelengths, 410.2, 434.1, 486.1 and 656.3 nanometres. These are known as the Balmer lines.
† There are three prominent absorption lines in the solar spectrum from neutral magnesium at the wavelengths 516.7, 517.3 and 518.4 nanometres.
5. SUNSPOTS
* Around the same time a British astronomer, John Evershed, and a French astronomer, Henri Deslandres, independently also devised similar instruments.
6. THE SPINNING SUN: THE DAY THE SUN FOUGHT BACK
* There is a twenty-first-century analogy to the hunts for Neptune and Vulcan: the search for dark matter. This search was triggered by unexplained observational characteristics of galaxies. These are collections of hundreds of billions of stars that are bound together by gravity, but the stars at the edge are rotating far quicker than our current understanding of physics predicts. Our best models show that the galaxies should fly apart, but this is something that we don’t see happening. Once again, either our theories are wrong or there is more matter than we can see, holding the stars in place. This extra matter is too dark to see, and has been given the creative name ‘dark matter’. Dark matter is an attractive solution because it is simpler to think that there is more matter to be found than to instead consider rewriting the laws we think govern the Universe.
9. BON VOYAGE
* The referees had actually not found any flaw in Parker’s calculations or mistakes in his logic, so there really was no reason to reject the work, but it was still unusual to ignore their decision.
* http://blog.chron.com/sciguy/2012/10/more-evidence-that-voyager-has-exited-the-solar-system/.
* As of July 2016.
10. SPACE AGE
* There is also the issue of ‘seeing’ – the bending of the light as it comes through the atmosphere, which degrades the image and causes stars to ‘twinkle’.
11. THE FLARE NECESSITIES
* Not to be confused with ‘Rocket Raccoon’, which is less a scientific instrument and more of a Marvel Comics character. ‘Rockoon’ has nothing to do with raccoons at all.
12. CORONAL MASS EJECTIONS
* The equation for kinetic energy is ½ mv2.
† The equation for gravitational potential energy is where G is the gravitational constant, M is the mass of the Earth, m is the mass of the ball and r is the Earth’s radius.