Caleb Scharf's Book on Black Holes Separates Science From Fiction

September 25, 2012

Sometime in the next year and a half, a glowing interstellar blob—possibly a star or a young solar system—will pass perilously close to the supermassive black hole at the center of the Milky Way galaxy. If it is sucked in, scientists will witness for the first time a significant “feeding event,” which will result in a massive release of energy that helps galaxies and stars evolve.

Science fiction books and films have long portrayed black holes as ominous and destructive, but in Caleb Scharf’s new book, "Gravity’s Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos," the astronomy professor explains that they can create as much as they consume. “Black holes regulate growth,” said Scharf. “As stuff falls into a black hole, a tremendous amount of energy is released. That energy plays a profoundly important role in the evolution of galaxies, the number of stars and the nature of the cosmic environment.”

Almost every galaxy has a supermassive black hole at its center. While mysteries about them abound, these black holes have distinct roles to play in the cosmos. Scharf calls them “gravity’s engines” because of the cyclical manner in which they suck matter and spew energy, a process that can be 50 times more efficient than nuclear fusion, said Scharf. “This process grows the black hole as much as it may govern the galaxy around it,” he said. “There is a balance between construction and destruction.”

If you add up the mass of the stars in the center of a galaxy and estimate the mass of the galaxy’s supermassive black hole, the stars have approximately 1,000 times more mass than the black hole. This cosmic relationship exists in the vast majority of galaxies, but there are exceptions, notably our own Milky Way.

“We live in a galaxy without this connection,” said Scharf. “Anytime you find something different in the cosmos, you question it. We live in what may be a somewhat unusual spot. There are other galaxies like ours, but they are not particularly numerous.”

Such mysteries motivated Scharf a decade ago to seek out what he referred to as a “teenage galaxy,” one that is still forming. Using NASA’s X-ray space telescope Chandra, he and his colleagues discovered a supermassive black hole surrounded by particles and hot gas flooding a young galaxy with energy 12 billion light years away—one of the furthest places Chandra has recorded. “The energy coming out of a black hole can play a major role in regulating the production of stars,” said Scharf, “which is critical because young galaxies like this are in states of constant assembly.”

Scharf, who has taught at Columbia since 2002, wrote a 2008 textbook, "Extra Solar Planets and Astrobiology," to help explain these emerging fields to his undergraduates. It won the 2011 Chambliss Award from the American Astronomical Society. Other universities, including Princeton and the University of California, Santa Cruz, offer their own courses based on the book. “The part I enjoyed most about writing my textbook was explaining the science embedded in the equations,” he said. “Science is all about storytelling. Even with algebra, you’re still constructing a story. And with black holes, there is a natural story to tell.”

Scharf began working on "Gravity’s Engines" because he realized that there was a tremendous science story to tell a non-scientific audience. He completed it in just five months, approaching each chapter like a research project, a valuable process because he was forced to step back and review the fundamentals of his specialty and weave the science into narrative. “I had to question my long-held assumptions and find revealing and interesting sources, while trying to transmit my own excitement for readers to pick up on.”

Scharf is already at work on his next book, "The Copernicus Complex," in which he tackles Earth’s cosmic significance. He plans to give context to our solar system’s “possibly unusual architecture” and explore microbial biology, cosmology, the science of inference, space exploration and more. Scharf also contributes regularly to "Scientific American," where his blog, “Life, Unbounded,” has had over a quarter-million visitors in the last year.

“Anytime I write about extremes and things difficult to conceptualize, I always come back to how tiny we are,” said Scharf. “It’s a good thing to be reminded of. I’ll do anything I can to help give people a cosmic perspective.”

—by Meghan Berry