The discovery was stunning enough to briefly dominate the headlines of virtually every major news website in the country (including this one): astronomers utilizing high-powered telescopes had identified seven Earth-sized planets orbiting a dwarf star, TRAPPIST-1, that could potentially harbor life only 40 light years from earth. It was a thrilling development, one that raised the odds of finding another habitable planet beyond our own, if not also discovering extraterrestrial life on another planet.
“The universe became a little less lonely yesterday,” says Meg Pickett, a theoretical astrophysicist and an associate professor of physics at Lawrence University in Appleton, Wisconsin.
But the question of what we can do to bridge the gap between the Earth and those seven planets—questions about how we determine whether any of them possess atmospheres to support human life, or whether they already support life, and how we might make contact if we do discover extraterrestrial life–is far more complicated. In a way, the real work begins now and may last for generations, if not for centuries.
The observational phase comes next and begins with follow-up surveys from space-based telescopes like the Kepler and Spitzer, as well as the Hubble and its replacement, the James Webb Space Telescope, scheduled to launch in the Fall of 2018. Such surveys could occur within the next five years or so. The Webb is capable of providing powerful spectrographs which could detect molecules such as water, methane, ozone and oxygen, and help determine the habitability of the Trappist-1 planets—particularly the three considered to be within the “habitable zone” that might harbor water on their surfaces.
“We won’t really ‘find life,’” says David R. Klassen, chair of the department of physics and astronomy at Rowan University in New Jersey. “Those measurements can’t really be made. If we can find ‘habitable’ (conditions), I think the significance is that we aren’t unique—that the conditions for life are more common that once believed.”
It’s possible that none of the planets around TRAPPIST-1 will be habitable—they’re close enough to the TRAPPIST-1 star to be tidally-locked to it, meaning one face would experience 24-hour daylight while the other side is in the dark. These differences in light exposure would create extreme temperature gradients across the planet, driving high winds and extreme radiation fluctuations that might make them inhospitable for sustaining life.
But as Pickett points out, we may wind up finding even more planets around TRAPPIST-1. The significance of finding seven Earth-like planets orbiting a single star, she says, “suggests that Earths are plentiful,” and adds to a rapidly growing catalog of roughly 3,600 other known exoplanets, with thousands more detected and waiting for confirmation. The actual number of exoplanets, Pickett says, could be in the billions or hundreds of billions.
“If there is liquid water present on these planets, then we can follow the example of our own planet—wherever there’s water, we find life,” Pickett says. “Life is tenacious.”
So what if we do find a habitable planet among that group? Klassen says that, for now, at least, regarding NASA’s goals, habitability is the “end game.” If you try to look ahead, to imagine things beyond that point, you risk veering more into speculation than science. But the speculation is fascinating enough that it’s hard to resist.
“How (life) would arise and survive in this astronomical environment is unclear,” Pickett says. “We won’t know for sure unless we go there.”
“It may be a hundred-miracle type of question.”
But how do we possibly get there? As NASA’s presentation revealed, to get there at lightspeed would take a manageable 39 years; to get there at the speed of a jet airplane would take 44 million years. At the moment, we simply don’t possess the technology to reach another star in “a reasonable period of time,” Pickett says. While the New Horizons spacecraft managed to reach Pluto in nine and a half years, for instance, it would take 54,000 years to reach Proxima Centauri, the nearest star to earth. The Juno spacecraft, which is headed to Jupiter, would take “only” 17,000 years. And none of those craft is large enough to transport humans even if the trip were feasible.
Which is where we require a miracle. Or perhaps, as Thomas Zurbuchen, associate administrator of NASA’s science mission directorate, said during NASA’s presentation, we need “so many miracles on the way. It may be a hundred-miracle type of question,” involving breakthroughs in nuclear propulsion and radiation protection. There is work being done, Zurbuchen says, on “the first five to ten of those miracles,” but it may take many lifetimes—and some failures–before we’re able to figure it all out.
“One possibility is that if we could improve our spectroscopy techniques further, we could make even more detailed studies of the atmospheres looking for tell-tale molecules,” Klassen says. “For example, large amounts of molecular oxygen would be an indication of photosynthetic life.”
One other possibility: The Breakthrough Starshot Initiative, which is working to design small spacecraft powered by solar sail and laser technology to reach 20 percent of light speed. Even then, Pickett says, the engineering is “at least 20-25 years away,” and “many in the astronomical community are skeptical” that it can even work.
But there is hope, and this is where the Search for Extra-Terrestrial Intelligence (SETI) Institute comes in. SETI, Pickett says, has ways to encode information in messages—much of it is based on mathematics. Send out a signal containing the first dozen or so prime numbers, and then teach simple instructions like 1+1=2, and you can establish a common language. So far, though, SETI’s scans of radio bands for transmissions from TRAPPIST-1’s system have revealed nothing. And even if we did find someone or something, a simple “Hello” message would take 40 years to transmit—and then would require another 40 years to wait for an answer.
“The lessons are that space is big, and we are still in the infancy of space exploration,” Pickett says, “and however fast we manage to go, we will—at least so far as we know—always be beholden to relativity.”