Fifteen percent of solar systems are like ours

Posted by Emma Woollacott

Astronomers have worked out that around 15 percent of stars host solar systems like our own, with several gas giant planets in the outer regions.

“Now we know our place in the universe,” said Ohio State University astronomer Scott Gaudi. “Solar systems like our own are not rare, but we’re not in the majority, either.”

Microlensing Follow-Up Network (MicroFUN) astronomers used gravitational microlensing, which occurs when one star happens to cross in front of another as seen from Earth. The nearer star magnifies the light from the more distant star like a lens. If planets are orbiting the lens star, they boost the magnification briefly as they pass by.

It's a particularly good way of detecting giant planets like Jupiter.

Although 15 percent might not seem like much, this is actually good news, says Gould. "With billions of stars out there, even narrowing the odds to 15 percent leaves a few hundred million systems that might be like ours," he said.

The conclusion is based on a simple statistical analysis: in the last four years, the MicroFUN survey has discovered only one solar system like our own.

“We’ve only found this one system, and we should have found about six by now - if every star had a solar system like Earth’s,” Gaudi said.

“While it is true that this initial determination is based on just one solar system and our final number could change a lot, this study shows that we can begin to make this measurement with the experiments we are doing today,” Gaudi added.

The conclusion could improve estimates of the likelihood of life elsewhere in the galaxy.
 

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