Koresko, a Caltech astronomer, presented his findings here today at a meeting of the American Astronomical Society.
The whole scheme is probably not conducive to planet formation, Koresko said in an interview.
Planets form in disks of dust that swirl around newborn stars. The star systems Koresko studied are at the right age for planet formation -- about 1 million years old. But some of the stars are so close to each other that their dust disks likely crash into each other, driving some of the dust into the stars or ejecting it into interstellar space.
Koresko thinks that any dust that tries to get together to make rocks, thought to be the seeds of planets, would be continually ripped apart.
"It's not clear whether planets could form under such conditions, or whether, once formed, they could survive," Koresko said. He added that these three-star systems would probably go to the bottom of the list of places where planet hunters will point their telescopes.
Scientists expect that planets could develop around stars that are in a binary configuration -- in which just two stars orbit each other.
Koresko examined 15 known binary star systems, all about 500 light-years from Earth. Seven of them turned out to be triple star systems.
The ratio can't be applied across the galaxy, he said, because he looked only in places where young stars are being formed in rapid-fire fashion. In fact, he said, these stellar nurseries are known to contain a higher percentage of binary star systems compared with more open regions of space, where stars tend to be older and more frequently on their own.
This disparity has long puzzled astronomers.
"Are stars tending to be formed as binaries and then the binaries are broken up as they evolve?" Koresko wonders. "Or perhaps we're able to find binaries more effectively [in the nurseries] because when the stars are young they are bright."
Knowing now that triple star systems are more prevalent only adds to the mystery, he said.
Each of these complex three-star systems likely formed in a single event, and much in the same way a lone star would form, when one cloud of gas and dust collapsed under its own gravity, Koresko said.
The research was done using the 33-foot (10-meter) Keck 1 telescope on Mauna Kea, Hawaii. It involved a complex system called "speckle holography" to generate high precision. Koresko said follow-up observations are needed to confirm his findings.
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