GRO J1655-40 is a binary star in the constellation Scorpius. It consists of an evolved F-type primary star and a massive, unseen companion, which is thought to be a black hole. They orbit each other every 2.6 days. [Credits: ESA, NASA, and Felix Mirabel]

Empire of the Stars, according to the author Arthur I. Miller, is the history of an idea. The idea is that of a black hole, a massive object that has collapsed into an unbelievably tiny region of space. Its gravity curves the space around it so strongly that not even light can escape.

The story focuses on a 1935 meeting of the Royal Astronomical Society in London where a young Indian astrophysicist Subrahmanyan Chandrasekhar - known as Chandra - presented a revolutionary paper.

At that time people accepted that when a star stopped shining, it collapsed by gravity into a small superdense body called a white dwarf. But Chandra's paper showed mathematically that there was an upper limit to the mass of a white dwarf. The paper does no more than calculate this limit, but astronomers realized that in this case, logically, if the mass of a star exceeded the limit, collapse would continue with nothing to stop it.

One of the world's premier astrophysicists, Sir Arthur Eddington, spoke after Chandra, making a point of ridiculing and dismissing the paper.

In telling the history, Miller describes the milestones on the road to acceptance of black holes into mainstream astrophysics. There are not only clear summaries of some of the work, but also vignettes about many of the prominent physicists of the day.

Intertwined with the black hole history is Chandra's own story. He was a child prodigy who went from Madras to Cambridge at nineteen. His uncle was the first Indian to win a Nobel Prize and Chandra was also aiming high. He developed his white dwarf theory on the ship as he sailed to England and arrived full of hope and ambition.

I'll say now that I found the book a pleasure to read as it wove its way through the personalities and ideas of this flowering of physics in the twentieth century. I'd certainly recommend it as a good read. Miller avoids technical terms so that the general reader should be able to follow the story and it moves along well.

But, oddly, Miller emphasizes two supposed consequences of the encounter between Chandra and Eddington.

The first is the personal consequences to both parties.

I wasn't convinced that there were any for Eddington, though Miller makes the case that Chandra was deeply hurt by the public ridicule from a man who had been one of his great heroes. Yet his career wasn't hampered, for at the outset he was wooed by both Harvard University and Yerkes Observatory near Chicago. He wrote definitive works on many important areas of physics, was an acclaimed teacher and won a Nobel prize. He saw his early brilliant insight vindicated and made some later contributions to black hole theory.

The second consequence was that the encounter "hindered progress in astrophysics for nearly half a century." Miller maintains that the conservative British astrophysicists were encouraged by Eddington's response to refuse "even to consider the idea that stars might collapse to nothing."

However I would say that the book itself refutes this assertion, for one of its main strands is the discoveries that made black holes acceptable. They took place over a period of decades and included the discovery of the neutron and then the idea of a neutron star, the understanding that stars shine by thermonuclear reactions in the core and that a supernova occurs when a massive star runs out of fuel.

I can't see how such an outrageous idea as a black hole could have been accepted without considerable groundwork and the book shows that even the people working on gravitational collapse didn't accept its reality.

For example, Miller describes the advance of astrophysics in the Soviet Union and tells how Lev Landau independently arrived at a proof of the white dwarf mass limit, yet didn't believe that stars collapsed into nothing.

In California Robert Oppenheimer and Hartland Snyder published a paper on gravitational collapse. When a star runs out of fuel, if nothing happens to reduce the mass, the gravitational contraction “will continue indefinitely.” Nonetheless Oppenheimer also rejected the idea that this would actually happen.

Even John Wheeler (who later invented the term black hole) refused to accept complete collapse, arguing in 1958 that it made no sense and there was no observational evidence for it.

Empire of the Stars, author: Arthur I. Miller, published by Little, Brown: 2005, ISBN: 0-316-72555-0

Oppenheimer, J.R. & Snyder, H. (1939), “On Continued Gravitational Contraction,”
Physical Review, vol. 56, Issue 5, pp. 455-459 09/1939