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Planet Quest
by Ken Croswell

Since the early days of astronomy, one question has always popped up: is anybody out there? Unfortunately, except in various Science-FIction movies, that question has not been answered yet. But another question related to that one has been answered: are there any planets out there? The answer to that is now yes.

In this book, subtitled "The Epic Discovery of Alien Solar Systems", Croswell takes a look at the search for planets, both in the past and the present, and offers some speculation on the future.

He starts off by giving a primer in planets, describing the characteristics of planets and orbits in our solar system. He follows that by looking at early theories of planetary formation and the early hunters of new planets in our solar system, including the non-existent Vulcan (thought to affect the orbit of Mercury until Einstein's Theory of Relativity provided the explanation) and Planet X (thought to affect the orbits of Uranus and Neptune until more accurate measurements of their orbits indicate that no Planet X is required to explain their orbits).

Croswell then crosses interstellar space to cover the search of extra-solar planets orbiting sun-like stars, the hope being that by discovering them, the odds of finding life elsewhere would be better. He explains how planets orbiting other stars are discovered by finding wobbles in the star's position.

Unfortunately, the shifts in the positions of the stars required to indicate that any planet is present is very small, leading to many false announcements of planets orbiting sun-like stars. So, it was a surprise when the announcement of the first actual planet orbiting a star was one orbiting a pulsar. Finally, a planet orbiting a 'normal' star was announced, which was a giant planet but unexpectedly in an orbit even smaller than Mercury's, throwing theories on planetary formation into doubt.

While telling the history of the discovery of those and other (real and false) planets, Croswell provides adequate background explanations to show what astronomers are looking for when examining stars for planets. So, even a person who knows only a little about astronomy should be able to follow the book quite well.

The book also features a high number of "personal quotations" by astronomers, rather than attributions in third person. I suppose one reason this was done was Croswell wanted to show that the field of 'planet hunting' is a very stressful one and the personality of astronomers can affect the outcome of searches.

Unfortunately, I found some of the diagrams in the book too simplified for my tastes. For example, one diagram shows Neptune pulling on Uranus by gravity, thus affecting the speed and orbit of Uranus. The diagram does not show that Uranus also tugs on Neptune (by Newton's Third Law of Motion), possibly giving readers the wrong impression on how planets affect each other.

Despite this, I found the book engrossing and a good way to find out what is happening in this branch of astronomy. Perhaps, in the near future, the instruments used to find planets may grow sensitive enough to reveal Earth-like planets and perhaps answer that age-old question about life in the universe.

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Planet Quest by Ken Croswell

Planet Quest
by Ken Croswell