As years pass, various interests wax and wane in astronomy. Some might says fads come and go. Early in the 20th century, there’s big interest for finding that second Earth–a blue and green planet somewhere in the universe where maybe aliens like us live. Our probes poke at Mars and try to tease out hints that life once existed there. Or maybe still does. And with a few recent hits and near misses, we look to stadium-sized rocks in our orbital neighborhood and wonder if our crash helmet will be enough next time.
John Percy’s book Understanding Variable Stars addresses none of today’s popular topics, really. He’s focused not on microbes, fossils, or skyfall, but on big game. Stars. And more, stars that change in brightness.
Why do stars change in brightness? It can happen when they are very young or very old. As it happens, stars pulse, blast, flare, flatten, sputter, spin, spill stuff onto other stars, eclipse, erupt, hide, reappear, degenerate, explode, and do all sorts of interesting things. Indeed, after I finished this book, I began to reflect that maybe our sun is the oddball. It just rises every morning and sets every evening and always comes up the same every day.
This is an advanced book for amateur astronomers. To get the most out of it, one will need a strong science background. Indeed, it reads like a textbook for an undergrad course in stellar astronomy. Lots of graphs. Lots of physics and some stellar chemistry. But an amateur with this book under her belt will be a force to be reckoned with in the world of AAVSO, the American Association of Variable Star Observers. And that means something because diligent amateurs, equipped with a good telescope, good viewing conditions, and a basic array of modern equipment, can make substantial contributions to stellar astronomy.
Let’s get back to that textbook thought. If this book is any indication of what it’s like to sit in one of Professor Percy’s classes, I would love to take Astro 261 Stellar Astronomy from the guy. He infuses just the right amount of history and personal interest. He communicates exuberance for his topic through text and data. Dr Percy loves astronomy, pure and simple.
Personally, I gravitate to the planetary regions of astronomy, but I borrowed this book from the university library just to broaden my horizons a bit. It’s good, especially for amateurs, to have a broad base of knowledge. I’m not sure why I needed to learn why the element lithium churns in the atmospheres of young stars and is barely found at all in the sun. But it was interesting to learn the up-to-date speculations about Eta Carinae. The first two chapters are as good an introduction to stars as I’ve seen anywhere. Chapter three sets the table for the topic in 32 pages. More than 200 pages breaks down most all types of variable stars as we know them–and this is the part where you really have to pay attention. I read this book in three weeks, and I certainly wouldn’t get top marks for the little I could recall.
I can’t imagine a better in-depth introduction to variable stars. If this branch of astronomy is your passion, this book needs a spot on your shelf. If you prefer galaxies, cosmology, or planets, it’s still a recommended read. How stars function and especially change will impact planets. What stars quadrillions of miles away from the Earth do is amazing. First, for how much information we can tease out of the universe just by watching it. Second, an appreciation that the sun is not a variable star. Third, for the implications of planet formation and eventually, I suppose, where the human race will settle after we leave the solar system. And then there’s just the wonder of it all. That last one’s enough for me.
The image is an infrared “movie” of Algol, a double star in which the components orbit almost edge on as seen from Earth. The dimmer of the two eclipses the brighter and even without a telescope, an observer can tell.