MYSTERY WIRE (AP) — Space exploration – mankind’s thirst to seek out far off worlds and learn more about the universe.
But what if there’s life out there doing the same thing?
Astronomers have found stars in our galaxy from where Earth may already have been spotted.
They took a technique used to look for life on other planets and flipped it around — so instead of looking to see what’s out there, they tried to see what places could see us.
One way humans look for potentially habitable planets is by watching them as they cross in front of the star they are orbiting, which dims the stars’ light slightly.
So the astronomers used the European Space Agency’s Gaia space telescope to turn that around, looking to see what star systems could watch Earth as it passes in front of the sun.
There’s a lot.
Astronomers calculated that 1,715 stars in our galactic neighborhood — and hundreds of probable Earth-like planets circling those stars — have had an unobstructed view of Earth, according to a study released Wednesday in the journal Nature.
“One thing about this geometry is that it’s actually where we don’t look for planets per se, because it’s in the crowded part of the plane,” says Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University and study lead author.
“So we are actually not as knowledgeable as we are about other parts of the sky about this region, but our paper basically gives people a really good reason to now look there. And it’s all based on this really old idea of SETI (Search for Extraterrestrial Intelligence), you know, if they could have found us already, SETI is hoping that those would be the people who would send us some signals.”
They looked at the 331,312 stars within 326 light-years of Earth. One light-year is 5.9 trillion miles.
The angle to see Earth pass in front of the sun is so small that only the 1,715 could see Earth at some point in the last 5,000 years, including 313 that no longer can see us because of shifting views.
Another 319 stars will be able to see Earth in the next 5,000 years, bringing the total to more than 2,000 star systems with an Earth view.
Some include a few star systems where scientists have already spotted Earth-like planets, prime candidates for contact.
Kaltenegger says there is one system she is especially hopeful for.
“TRAPPIST-1 is always one of the favorites, right, because it has four planets in the habitable zone that are Earth sized,” she says.
“And it can’t see us yet. So that’s actually, for TRAPPIST, a really interesting thing. Because we can see it, but…they can only see us in about 1,600 years.”
If there is alien life in TRAPPIST-1, it will be a long time before they know we are here.
So should we try and make contact with these star systems in the hope there’s something there to hear our messages?
Some experts, including the late Stephen Hawking, warn against reaching out to aliens because they could harm us.
But Kaltenegger says it doesn’t matter. If those planets have sufficiently advanced life, they already know we’re here.
“Since two billion years ago, you could know that there’s life on the planet because of the bio-signatures, because of the oxygen that we breathe, right? So hiding is not really an option,” she explains.
“So whether you send a signal or not, they will be clear that there’s life on this planet if they have the same knowledge we do, right? And I assume, again, if you’re worried about somebody coming and eating you, you’re worried about a technological advanced civilization who would travel that distance.”
So if they are out there, why haven’t we heard from them?
It takes a long time for messages and life to travel between stars and civilizations might not last long.
Perhaps life in the cosmos could just be rare. Or maybe curiosity is simply a human-only trait.
But Kaltenneger still has hope that somewhere, out there, other life forms are trying to make contact.
“When I look up at the sky, it just looks a little bit friendlier because it’s like maybe somebody is waving, we just don’t know yet.”