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Starz in the Hood

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

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“I said, ‘Phil, do the numbers now!’ ” Henry recalls. It took only a few weeks to determine that the star, which goes by the unassuming tag GJ1061, was just 12 light-years away, making it the 20th nearest star—scarcely three times farther than our closest neighbor, the Alpha Centauri system, which includes the stars Alpha Centauri A, Alpha Centauri B, and, closest of all, Proxima Centauri.

“I’ll let you in on a secret,” Henry says. “We have better numbers now, and they show that it’s actually even closer. A few years ago, no one knew it was there.” The team gave the star another, newer name: RECONS 1.

The discovery led Henry to some simple calculations. Within five parsecs, or about 100 trillion miles, we know of 60 stars and one planet beside our own solar system. Let’s say this represents most, if not all, of the objects actually out there. Simply assuming that the density of stars remains the same out to 10 parsecs, there should be roughly 500 stars within that volume of space. Yet astronomers have counted only about 315.

Within 20 parsecs, there should be about 4,000 stars. “We know of about half that,” Henry says. “I like to compare it to a baseball field, where you have quite a few infielders but far fewer in the outfield. In fact, the density of players in the outfield of space should be about the same as the infield. We just haven’t located them yet. People ask me, ‘Why don’t we know where the rest of them are?’ The simple answer is ‘Because there are a lot of dots in the sky.’ It takes time to map everything out, and we just haven’t been at it that long.”

Astronomers also don’t always share information as effectively as they could, so it may be that parallax data for other nearby stars actually will be found in Ianna’s or some other researcher’s files. Or it could be that different astronomers have pieces of the puzzle that, once put together, could reveal stars much closer than anyone thought. So Backman’s team will build an unprecedented database from as much information as they can round up from the existing scientific literature, and make it available to astronomers and the general public over the Internet. The team’s search for relevant information has already turned up other candidate nearby stars. An expected influx of additional data from new sky mapping projects such as the Sloan Digital Sky Survey—which aims to chart more than a hundred million celestial objects, including stars, galaxies, and quasars—should yield even more discoveries.

The second element of NStars calls for additional research—using telescopes around the world to identify “new” nearby stars based on their parallaxes and to learn more about those that are already known. University of Texas astronomer Fritz Benedict, for instance, plans to seek funding to examine about 500 stars for signs that they are binary, or double stars; he expects that around 20 percent will be. Researchers could then exclude those stars from the list of candidates for planet hunting, because stable planets are unlikely to form in binary systems.

The research will have a wider purpose than just adding to the roster of nearby stars, says Benedict. “It’s not only filling in the blanks on our star catalogs, but also filling in our understanding of the way solar systems might work.”

The idea of NStars had so much appeal that when NASA launched the project last year, the National Science Foundation quickly offered to contribute half the initial funding of $1.2 million. By October, the funding agencies had received around 80 proposals, twice as many as they had expected, which led them to try to scrounge up more money.

Backman and Henry sound like kids on Christmas Eve when they talk about the wonders NStars should soon reveal. “I’ve been waiting for this for 10 years,” beams Henry. “I’m sure we will find new things, all kinds of crazy things. The nearest star, Proxima Centauri, may not be the nearest star. It’s really hard to guess what we’re going to find.”

But he hazards a guess anyway. Henry figures that most of the 2,000 or so uncounted stars within 25 parsecs of us will turn out to be faint red dwarfs about the size of Jupiter. Stellar censuses suggest that these dim objects, which are far fainter than the sun, dominate the star population, and our own neighborhood should be no exception. Although such stars shine too feebly to offer much hope of finding planets suitable for life, Berkeley’s Debra Fischer and her planet-hunting colleagues have already found one planet revolving about a red dwarf. They believe that most red dwarfs—in fact most stars—sport planets of some type.

About Michael Milstein

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

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