The Black Hole at the Center of our Galaxy by Fulvio Melia, Princeton, $29.95/拢19.95, ISBN 0691095051 Reviewed by Marcus Chown
YOU have to feel for Arizona astronomer Fulvio Melia who could only come up with The Black Hole at the Center of our Galaxy as the title for his book. Isn鈥檛 it about time astronomers invented a decent name for the black hole skulking at the heart of the Milky Way? After all, it is the most remarkable object in our galaxy. And, at almost 3 million times the mass of the sun, it鈥檚 the only supermassive black hole in our cosmic backyard. Astronomers call it Sagittarius A*, but that hardly paints a vivid picture of the star-swallowing, light-bending, time-slowing monstrosity lurking a mere 28,000 light years from your front door.
Despite the handicap of not having a decent name for his book鈥檚 principal subject, Melia covers just about all that is known about Sagittarius A*. The key to understanding the object turns out to be the complex environment in which it sits. Those environs are criss-crossed by gossamer filaments of gas, one of which is thought to be the remnant of a star squeezed so pencil-thin by a close encounter with the central behemoth that it exploded with the force of up to 100 normal supernovae.
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The most exciting possibility raised by Melia is that, within the next decade, Sagittarius A* will be imaged with an array of terrestrial telescopes. The characteristic shadow of the black hole, determined by light bent in its ultra-strong gravity, should provide the best proof yet of the existence of black holes.
Melia presents a thorough and comprehensive scientific overview of Sagittarius A*. The writing, however, is a little cumbersome and jargon-laden. It could have done with some editing. Judge for yourself. 鈥淲hen we measure the velocity of stars and the swirling gas clouds surrounding the nucleus,鈥� writes Melia, 鈥渨e uncover a velocity profile with a well-defined center in this region, much as the Sun acts as a centroid for the motion of the planets within our solar system.鈥� And that鈥檚 just the first page.