Miss Leavitt's Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe

Allan Sandage, the respected astronomer and protégé of Edwin Hubble, once said: "What are galaxies? No one knew before 1900. Very few people knew in 1920. All astronomers knew after 1924." Miss Henrietta Leavitt died in 1921. Working for years at the Harvard College Observatory under the noted astronomer Edward Pickering, this nearly forgotten observatory assistant, a 'computer' (one that does computations by hand), provided a tool critical to unraveling the most basic question facing astronomers in the early twentieth century. Was the Milky Way essentially the entire universe, or was the Milky Way just one of many large clusters of stars? These hypothetical clusters went by various names: island universes, nebulae, and galaxies. How could one demonstrate that some stars were in a nearby cluster, while others were actually much farther away? Triangulation methods, a trigonometric approach, only worked for the sun and a few nearby stars. Is a dim star a bright star that is far away, or is a dim star simply a dim star that is nearby? This short book, Miss Leavitt's Stars, is less biography, and more history and science than the title might suggest. Too little is known about Henrietta Leavitt herself. We do know that Miss Leavitt carefully analyzed the brightness of variables stars (those that brighten and dim over some period) in the Small Magellanic Cloud. Subsequently, she discovered a remarkable relationship between the brightness of individual stars and the lengths of their periods. The brighter the variable star, the longer the period. Furthermore, since the Magellanic variables are probably all about the same distance from the earth, their periods are apparently associated with their actual light emission. What all this means is that by measuring the period (the rhythm of brightening and dimming) one could determine the intrinsic brightness of a variable star. In turn, by comparing this calculated intrinsic brightness to the observed brightness an astronomer can determine how far away the star actually is. This breakthrough fueled the competition among astronomers to resolve the size of the universe. The ongoing debate between Harlow Shapley and Edwin Hubble dominates the second half of this short book. Hubble wins, and the concept of a galaxy becomes commonplace. Even more remarkable, distant galaxies are shown to be accelerating away: the universe is expanding at a rate determined by the Hubble Constant. I like the quote about Edwin Hubble from a hometown newspaper: Youth who left Ozark Mountains to study stars causes Einstein to change his mind. George Johnson writes with a clarity and precision not always found in science books for the layman. Miss Leavitt's Stars is a delightful blend of biography, history, and astronomy. Trivia: I was once a computer for a month. As a new geophysicist, I worked on a seismic crew in the Louisiana swamps for a year, rotating between various crew positions each month to gain fir

This is a great little book. In 130 pages of well-crafted prose, the author recounts the history of one of the most exciting periods in modern astronomy. Concentrating mainly on the early decades of the twentieth century, he explores astronomers' efforts to understand the size and structure of the universe. As the book's title suggests, Miss Leavitt's stars, i.e., Cepheid variables, play a very important role in this quest. However, according to the author, so little is known about Miss Leavitt's life per se that the book's subtitle is an exaggeration: the book is more about early twentieth century astronomy and much less about Miss Leavitt's life. Scientific principles are very clearly explained using simple analogies. No mathematical formulas are used anywhere in the book - an advantage or a disadvantage, depending on your point of view. Written in a most engaging style, this book would be of interest to anyone, but especially science/astronomy buffs.

This somewhat short book is a treasure trove for anyone seeking an inside look at astronomy early in the 20th century. The author presents some interesting insights into the intertwined careers of Henrietta Swan Leavitt, Pickering, Shapely and Hubble.

No study of history - no study of scientific discovery - is complete without recognizing how women helped shaped our knowledge of the world, the heavens and society. As more and more women, such as "Miss Leavitt," are recognized for their dediction to scientific discovery and other endeavors - just imagine what wonderful insights we have yet to learn! Too many of these stories remain untold. Thank you George Johnson for telling this one. "Miss Leavitt's Stars" belongs on every young woman's bookshelf and should be read to even the youngest girls - so she, too, may reach for the stars. (Review by: Marion E. Gold, author of "Top Cops: Profiles of Women in Command" and "Personal Publicity Planner: A Guide to Marketing YOU.")

If you look up at the night sky (unobscured, if possible, by city lights), you cannot help but see that some stars are bright and some are barely perceptible. There are explanations for these differences; a bright star may be an ordinary star but simply closer, or a bright star might be at an ordinary distance but simply bigger. A big part of the challenge of astronomy is trying to figure out just this sort of problem, because it involves basic measurements of our universe. One of the greatest breakthroughs on the way to understanding how to measure stellar distances was made by Henrietta Swan Leavitt, and if you have never heard this name, there are many reasons, all of them a little embarrassing. In _Miss Leavitt's Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe_ (Atlas Books / W. W. Norton), George Johnson has brought Leavitt to us, so that we can consider what she accomplished, and why she remains obscure. There is not actually much material on Leavitt here; this is a small book to begin with, and few of the pages actually have to do with her life. Johnson himself says she deserves a proper biography, but unless some heretofore secret material is found, she won't get one. She didn't leave diaries or memoirs, and there are few letters. What she left astronomers was a celestial yardstick, and it was used to change fundamentally our knowledge of the size and age of the universe we inhabit. Photography became a great help in astronomy, and eventually Harvard had a half million glass plates that were a precise a record of the night sky. But this was very raw data. To analyze the images, the director of the Harvard observatory, Edward Pickering, employed computers. A computer at that time was not an electronic gadget, but a human, a person who was hired to compute, when computing was monotonous and repetitive work. Leavitt was merely a computer, paid a minimal wage to do the drudgery of looking at the plates and toting up the brightness, color, and position star by star. Astronomy certainly was benefited by Leavitt's powers of observation, but she is one of the greats in astronomy because she organized her observations in an exceedingly useful and explicatory way. She concentrated her thinking on variables known as Cepheids (the first one having been found a hundred years before in the constellation Cepheus). She tallied up these stars, their brightness, and their rate of variation, and found that rate varied with brightness. A Cepheid that had a certain rate had a certain brightness, and this was the case whether it was distant or close. If two stars of the same rate appeared to have different brightness, it was only a matter of their different distances. Astronomers had a new measuring tool. Johnson's book explains how over the centuries astronomers first were able to measure the size of the Earth, then the distance to the Moon, to the Sun, to more distant stars, and to galaxies. He shows Lea