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Starz in the Hood

There are more stars in our celestial backyard than we once thought.

One day while in junior high school in the late 1960s, Dana Backman strayed into the adult section of his local library, wondering what sort of books adults read that weren’t available on the other side of the building. One of them was Habitable Planets for Man, written by astronomer Stephen Dole. A pioneering report commissioned by the RAND Corporation years before the first moonshot, Dole’s book assessed the possibility that planets suitable for human colonization were circling stars other than our sun.

“I was really just a science fiction fan at that point, but this was real stuff,” Backman recalls of his teenage discovery. “I was fascinated. I ate it up. I memorized it.”

Based on the ages and masses of stars in the galaxy and the many criteria necessary for habitable planets—water, an atmosphere with oxygen, light, certain chemicals, some gravity but not too much—the book estimated that up to 10 stars within 20 light-years of Earth may have human-friendly planets orbiting them. Especially striking to Backman was the suggestion that planet-bearing stars may be relatively unimpressive to look at. Indeed, an intelligent being on a planet circling the nearest star, about four light-years away from us, would regard our sun as pretty run-of-the-mill.

Later, while studying astronomy in college and graduate school, Backman was puzzled by the fact that most other researchers showed little interest in our stellar neighbors, preferring instead to look toward the far edges of the universe. When he talked excitedly about the possibility of planets beyond our solar system, other scientists looked at him as if he were reporting a fleet of UFOs. Still, he wondered to himself what astronomers must be missing.

Now he thinks he knows: Stars. Lots of ’em.

Today, Backman is one of the principal scientists behind a new NASA and National Science Foundation research initiative called the Nearby Stars Project, which seeks to fill a gaping hole in our knowledge of our own celestial neighborhood by cataloging stars within 25 parsecs, or about 80 light-years, of the sun. Rough estimates suggest that astronomers have measured the distances to only about half the stars within that range. The rest have yet to be recognized as nearby objects. A good number of them are perfectly visible, may even have a name, yet they remain anonymous, hidden in the vast crowd of more distant stars like an astronomer’s version of “Where’s Waldo?”

Ironically, nearby stars are the best places to look for planets beyond our solar system—the kind of planets that once earned Backman funny looks from his colleagues but which now make headlines around the world. The stars we should know best, it turns out, we hardly know at all.

“To be told that half the stars in our neighborhood are basically missing is something of a shock,” says Harley Thronson, a senior program scientist at NASA headquarters in Washington, D.C., who initially fostered the Nearby Stars Project, also called NStars. It’s also “a big handicap when you’re planning multimillion-dollar missions to look for planets around such stars. It means you don’t know where to look.”

Cataloging stars is not a new idea, but the NStars project will compile computerized dossiers packed with information never before included in conventional star catalogs—details such as a star’s age and the amount of dust swirling around it—that bear on the ability to support Earth-like planets. If such details are lacking, the project will sponsor research to nail them down. “This isn’t a matter of just punching numbers into a computer,” says Backman. “It’s a matter of aggressively identifying what we need to know but don’t know, and going after it.”

Researchers eager to test the limits of bigger and better telescopes have routinely skipped past the ho-hum objects close to home and focused instead on the biggest, hottest, and most distant attractions in the universe. Neutron stars, supernovae, and other stellar exotica make up only a small fraction of the population of stars, but for several decades they’ve been the most attractive objects to study, according to Backman, who today is a professor of astronomy at Franklin and Marshall College in Lancaster, Pennsylvania, with a dual appointment at NASA’s Ames Research Center in California.

About Michael Milstein

Michael Milstein is a freelance writer who specializes in science. He lives in Portland, Oregon.

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