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When exoplanets block starlight as it passes, some of that light is filtered through the atmosphere. Energy and light interact with molecules and atoms on that planet, and when light reaches the astronomer’s telescope, scientists can determine whether it interacts with chemicals such as oxygen or methane.
The combination of the two, Kaltenegger says, is a fingerprint for life.
“It’s really interesting that people could see that Earth was a habitable planet since about 2,000 billion years ago [ago], as a result of atmospheric oxygen, ”he says.
The idea of studying transits to find out if we’re on someone else’s radar isn’t really new. Kaltenegger attributed much of his inspiration to the SETI Institute in the 1960s, a plan that continues to seek extraterrestrial intelligence.
In 1960, he was the first person to attempt to detect a radio astronomer named Frank D. Drake radio transmissions between stars, Based on 11 light-years and two stars similar to the age of our sun. Although this attempt was a success, scientists and enthusiasts have continued to look for such signs ever since.
But whether the signals we send are being transmitted is another matter. In a new study, Kaltenegger and Faherty report that man-made radio waves have passed over the nearest 75 stars already on the list.
Even though humans have been transmitting radio waves for 100 years, this is nothing compared to the evolution of the planet Earth billions of years ago.
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