“We're talking billions, we're talking tens of billions. Even if I isolate the population to really the ones that we're very interested in, those that could potentially harbor life as we know it, that number is in excess of 10 billion in our galaxy alone.”
Since Kepler launched in 2009, 21 planets less than twice the size of Earth have been discovered in the habitable zones of their stars. The light and dark green shaded regions indicate the conservative and optimistic habitable zone.
The NASA Kepler mission scientists have confirmed a record haul of exoplanets: 1,284. The objects were all spotted in the patch of sky between the constellations of Cygnus and Lyra, and the announcement more than doubles the number of exoplanets, or a planet that orbits a star other than the sun, known to science.
So what does this mean for scientists who are searching the universe for signs of extra-terrestrial life? Well, according to Natalie Batalha, Kepler Mission Scientist at NASA Ames Research Center, that there are way more planets capable of hosting life than previously confirmed.
“We're talking billions, we're talking tens of billions,” Batalha says. “Even if I isolate the population to really the ones that we're very interested in, those that could potentially harbor life as we know it, that number is in excess of 10 billion in our galaxy alone.”
The discovery of these billions of exoplanets is a result of work done by scientists in NASA’s Kepler mission.
“We're taking a census of sorts,” Batalha says. “It's like calling up a thousand people and finding out who they're voting for and extrapolating that to the larger population. We’re surveying about 200,000 stars, looking at the planets that are orbiting them at least within what we call one astronomical unit — kind of an earth orbit and inward, and then trying to understand based on those results what the population of planets is in the galaxy.”
Batalha says she and others on her team have long suspected the existence of these planets based on periodic dimmings of light and other data they’ve collected, but they still had to do a lot of work to confirm their suspicions.
“As we look at these discoveries that are rolling in from Kepler and we crunched the numbers, we quickly realized that every star out there has at least one exoplanet orbiting it,” Batalha says.
Now, with confirmation of such a huge number of planets out there potentially capable of harboring life, Batalha says she thinks it’s almost a certainty that life outside earth exists.
“The reality is we don't know, right. I mean, we've got these goldilocks worlds — these are planets where there's the possibility that liquid water could pool on the surface. But that doesn't tell you what fraction of those are truly habitable environments where there is liquid water and where life could flourish,” Batalha says. “My impression is that microbial life is going to be ubiquitous on these worlds whether or not there's additional complexity or intelligent life … I don't know — maybe that is even rarer still … But time will tell.”
One thing Batalha is particularly interested in is learning more about planets that are much older than earth.
“I'm intrigued by the idea that there are planets out there that are twice the age of the earth,” Batalha says, “I wonder, you know, given that much time to evolve complexity and evolve life, what are the possibilities?”
So what’s next for scientists studying exoplanets? Batalha says the James Webb Space Telescope will be used to study something called transmission spectroscopy — a technique that studies a planet’s atmosphere by observing starlight filtering through that planet’s atmosphere as it transits across the disk of its star.
“The James Webb Space Telescope will be able to catch that light, spread it out into a spectrum and see those chemical fingerprints, and that's going to tell us what those atmospheres are made out of,” Batalha says. “Now the big question is, can it do that for potentially habitable — earth-sized planets? And there i'm kind of skeptical. I think James Webb is going to be really great at characterizing the atmospheres of the Neptunes, the sub-Neptunes, and, if we get lucky, maybe a smaller planet like Earth. But I think that remains to be seen. We'd have to get really lucky.”