Scientists are searching for signs of extraterrestrial life, but what if extraterrestrials are looking for us and we’re just not listening properly?
Astrophysicists René Heller of the Institute for Astrophysics in Göttingen, Germany, and Ralph Pudritz of McMaster University in Ontario, believe that one of the methods we use to search for life in our galaxy may also be used by extraterrestrials. And that means we should refine our listening skills.
To do that, we have to start listening in the right area.
Here’s how it works:
In order to determine if a planet is orbiting a star, astronomers use the stellar transit method. If a planet orbits a star, it will transit — or pass in front of — said star. This causes a minute dipping in starlight that is detectable only by special telescopes, including the Kepler Space Telescope. But it goes on from there: the field of searching for exoplanets has improved so much in recent years, that scientists are are now capable of detecting the chemical signatures of life in the atmospheres of exoplanets, called stellar spectroscopy. The scientists believe that other alien civilizations may be doing the same thing.
“It’s impossible to predict whether extraterrestrials use the same observational techniques as we do,” said Heller. “But they will have to deal with the same physical principles as we do, and Earth’s solar transits are an obvious method to detect us.”
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When looking for transits, there is a particular area — called a “transit zone” — where astronomers will find an orbiting planet. It’s essentially a narrow strip on the plane of the planet’s orbit. So extraterrestrials would be searching that zone to see if a planet was transiting our small star. And, perhaps, they’ve already detected chemical emissions that indicated — even long ago — that life exists on our planet. They may have even sent a signal.
So the key to increasing the likelihood of receiving a signal is to listen for transmissions within Earth’s own transit zone, the scientists believe.
“If any of these planets host intelligent observers, they could have identified Earth as a habitable, even as a living world long ago and we could be receiving their broadcasts today,” the researchers said.
It’s not that there are no programs in place to listen for alien transmissions. The SETI Institute has been searching for signals for more than 40 years. Around the world, other programs are doing the same thing.
We “listen” for these transmissions using powerful radio telescopes that are able to pierce interstellar dust and debris and pick up faint transmissions (think, the movie Contact based on the Carl Sagan book of the same name).
As for the likelihood of receiving a transmission. Pudritz said that they specifically left that out of their paper. And that’s because there are just so many things to consider. Searching for microbes is somewhat straightforward: we’ve learned that life exists in all corners of our own planet, even in the harshest conditions.
“But intelligence is entirely different,” Pudritz said.
Still, Pudritz is optimistic that we will soon find some signs of life in our galaxy. He believes that the best chances we have will come from astronomical surveys.
“The search for life in the cosmos is now in full gear,” Pudritz said.