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Scientists have completed the largest search to date for signs of life outside of our solar system.
Using a radio telescope in Australia, scientists studied around 10.3 million stars. They did not find life - not yet, at least.
Researchers were looking for so-called "technosignatures" - communications signals that may come from alien beings.
Using the Murchison Widefield Array (MWA) telescope in Western Australia, scientists searched for sound waves in the star system of Vela. The findings were published recently in Publications of the Astronomical Society of Australia.
Chenoa Tremblay is an astrophysicist with Australia's national science agency. Tremblay noted that the findings were "not surprising."
"The search for life outside of our solar system is a big challenge," Tremblay added. "We don't know when, how, where or what type of signal we may receive to get an indication that we are not alone in the galaxy."
The search was 100 times deeper and broader than ever before, noted astrophysicist Steven Tingay of Curtin University in Australia. Still, it involved few stars in the universe.
"Ten million stars does seem like a lot. However, our best evaluation is that there are around 100 billion stars (in the Milky Way galaxy). So we have only looked at about 0.001% of our galaxy," Tremblay said. "Pretend the oceans contained only 30 fish and we tried to look for them by testing an area the size of a backyard swimming pool. The chances of finding one of those fish would have been small."
Another kind of telescope, the Square Kilometer Array (SKA), promises to help search for technosignatures soon.
"What is important is ... always going deeper and further," Tingay said. "There is always that chance that the next observation will be the one that turns up something, even if you expect nothing. Science can be surprising, so the important thing is to keep looking."
I'm John Russell.
Will Dunham reported on this story for Reuters. John Russell adapted it for Learning English. Hai Do was the editor.
