U.S. researchers have narrowed down their search for radio signals from intelligent life among the stars.
Using NASA’s Kepler data, the scientists selected 86 stars to investigate, choosing from a list of 1,235 known planets. They picked stars with several planets, or planets that may have liquid water or other Earth-like conditions.
“We no longer have to guess about whether we are targeting Earth-like environments, we know it with certainty,” said University of California-Berkeley physicist Dan Werthimer in a press release.
The team examined the stars for intelligent radio signals using the Green Bank Telescope in West Virginia.
Fewer than one in a million Milky Way stars should harbor such advanced civilizations, the scientists estimated. Since there are so many stars out there, these odds mean that millions of them may have civilizations.
The telescope detected radio emissions with a frequency range between those of cell phones and TV. Next, the scientists searched through the data for any signs of artificially created signals.
“We didn’t find ET, but we were able to use this statistical sample to, for the first time, put rather explicit limits on the presence of intelligent civilizations transmitting in the radio band where we searched,” said study co-author Andrew Siemion, also at UC Berkeley, in the release.
The stars are so far away that we would only receive an intelligent radio signal from them if they deliberately sent it to us. In the future, scientists hope to have more powerful instruments that can pick up accidental radio signals from other civilizations.
In the future, if two planets align just right, we may be able to pick up on communication between them.
“The Kepler mission taught us there are a trillion planets in our Milky Way galaxy, more planets than there are stars,” Werthimer said. “Some day, Earthlings might contact civilizations billions of years ahead of us.”
The paper was published in the Astrophysical Journal.
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