Are the aliens listening to Earth? The latest research assumes that around 1,700 stars are in the right position to have discovered life on Earth 5,000 years ago.
Radio transmissions from space
In 1960, a radio astronomer named Frank D. Drake was the first to attempt to detect interstellar radio transmissions. He focused on two stars that were 11 light-years away and similar in age to our sun. Although this attempt was unsuccessful, scientists and amateurs have continued to search for such signals ever since.
Whether the signals that we send in turn arrive is a completely different question. In a new study, Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University, and Jackie Faherty of the American Museum of Natural History report that human-made radio waves have already reached the 75 closest stars on their list of interesting exoplanets. Even if humans have been sending out radio waves for about 100 years, this is nothing compared to the billions of years that the earth has already existed as a planet.
With thousands of exoplanets orbiting other stars in our universe already found, it is quite possible that we would have seen life on other planets come and go without realizing it. “The universe is dynamic,” says Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University and lead author of the study. “Stars move, we move. First the earth moves around the sun, but the sun moves around the center of our galaxy.”
In the “Goldilocks Zone”
Statistically, one in four stars has a planet that is in the “Goldilocks Zone” – not too hot, not too cold, and just far enough from the star for life to be possible. But how can we tell if distant exoplanets meet these criteria?
Much of our own solar neighborhood is still unexplored, but this is where missions like TESS, Gaia, and Kepler come in. The TESS project spends months examining different sectors of the universe for exoplanets, and Gaia is trying to create a three-dimensional map of the entire Milky Way. Kepler, on the other hand, was developed to observe a patch of sky over long periods of time – the perfect way to find exoplanets using the transit method.
Space is huge
“The really big advantage of both Kepler and Gaia is that they are able to gaze at the stars for long periods of time,” says Douglas Caldwell, a SETI researcher for the Kepler mission. Caldwell says missions dedicated to such specific scientific goals provide a type of precision that holds promise for future astronomical discoveries.
“Space is really huge, and these stars are all very far from us compared to what we are used to as humans,” he says. “We look at our closest neighbors and try, so to speak, to understand our smaller neighborhood in the galaxy.”
While we may still be invisible to extraterrestrial civilizations from where we stand today, the researchers think it’s nice to think that one day we might at least be able to say “hello”.