If you wanted to build a space telescope to see another Earth orbiting another star—in the words of Carl Sagan, another “pale blue dot” that could be searched for signs of life—how big and expensive would such a telescope be? Just a decade ago the answer boiled down to “too big” and “too expensive,” leading NASA and other space agencies to postpone for at least a generation plans to build giant, budget-busting observatories to snap pictures of Earth’s possible cosmic doppelgangers. Now, however, a consortium of privately funded research institutions is offering a markedly different conclusion. For less than $50 million, the effort’s planners say, a telescope small enough to fit in the trunk of a compact car could launch by the end of the decade on a historic mission to image another Earth-like planet. They call the plan Project Blue.
According to Jon Morse, former head of NASA’s astrophysics program and current CEO of a research organization called the BoldlyGo Institute, ongoing technological progress makes this plan viable. “There’s a lot more capability out there for lower cost than there was 10 years ago, whether in spacecraft performance or in the availability of launch vehicles for access to space,” Morse says. BoldlyGo has partnered with another organization, Mission Centaur, to lead Project Blue.
Additionally, the thousands of worlds discovered by NASA’s planet-hunting Kepler mission strongly suggest that “there should be as many small planets like the Earth as there are stars,” Morse explains, meaning that to see one astronomers should not need to build a gargantuan telescope that could peer clear across the galaxy.
There’s just one catch. Project Blue’s proposed telescope would have a light-gathering mirror just half a meter wide—so small that it could only look for Earth-like planets around two stars: the Sun-like Alpha Centauri A and Alpha Centauri B, which along with the red dwarf Proxima Centauri form the nearest star system to our own at just over four light-years away. Proxima Centauri made headlines earlier this year when astronomers discovered a planet with a mass similar to Earth’s in a not-too-hot, not-too-cold “habitable zone.” Alas, this newfound world orbits so close to its small, dim star that it will be very difficult to image with a space telescope. No one yet knows whether any planets orbit Alpha Centauri A or B, but because both stars are so much larger and brighter than Proxima, their habitable zones are much further out, allowing any as-yet-undiscovered worlds to be more easily seen.
“Looking around the very nearest Sun-like stars is the next logical step in the search for another Earth,” says Supriya Chakrabarti, an astronomer at the University of Massachusetts, Lowell, who is developing planet-imaging technologies for Project Blue. “The task is daunting, but we have systematically picked off the technologies we must mature to do this.”
Blinded by the Light
A habitable planet around Alpha Centauri would appear approximately 10 billion times dimmer than either of the system’s Sun-like stars. It would also be swimming in stellar glare, meaning Project Blue’s telescope would have to filter out on the order of 10 billion stellar photons to gather just one photon of planetary light. And Alpha Centauri’s twin system poses an additional challenge for imaging, as any telescope must deal with the glare of not one but two nearby stars. In theory a starlight-blocking device called a coronagraph could perform this extreme feat of optical wizardry—but in practice all coronagraphs tend to leak trickles of unwanted starlight into a telescope’s delicate sensors. The only way to plug the leaks is to make a practically perfect coronagraph, then to feed it with a beam of starlight shaped to similar perfection both by deformable mirrors as well as by the extremely precise and stable pointing of a telescope. Reaching a seamless synergy among this holy trinity—high-performance coronagraph, deformable mirror and instrumental stability—is so formidable it has scarcely been achieved in laboratories here on Earth, and has never even been attempted on a telescope in space.
For years Chakrabarti and his colleagues have been pursuing a middle way between the laboratory and orbit, using NASA funding to conduct low-cost test flights of these advanced optics technologies with small suborbital rockets and high-altitude balloons that reach the edge of outer space. Roughly half of the $50 million Project Blue hopes to raise will support further development and testing of coronagraph systems, with the rest going to building flight hardware, booking a rocket and conducting the mission. Work on finalizing the telescope’s design will begin in 2017.
Lofted into low-Earth orbit in 2019 or 2020, the tiny telescope would spend two years staring at Alpha Centauri’s two stars, then stacking up tens of thousands of sequential images to amplify the appearance of any promising dots and to confirm their planethood by watching them whirl around their respective stars. Another project partner, the SETI Institute in California, will process, archive and publicly distribute the mission’s data, Morse says. Project Blue is also looking into additional partnerships with NASA as well as other space agencies and science institutions. Crowdfunding from interested people could raise a portion of the required funds, he adds, although much would probably have to come from wealthy donors and foundations.
As suggested by its name, Project Blue plans to optimize its telescope to study planets in blue light—a color that can readily communicate the presence or absence of oceans or clouds. More in-depth studies that could seek signs of life in the atmospheres or on the surfaces of any worlds around Alpha Centauri would have to wait, however, for the development of bigger and more expensive telescopes. NASA is currently considering multiple concepts for such mega-observatories that could conceivably fly in a few decades, but these proposed telescopes—like others the agency has evaluated and abandoned in decades past—have no guarantee of becoming reality.
Waiting for a Revolution
Despite NASA’s on-again, off-again history with pursuing big and ambitious planet-imaging space telescopes, to date the agency remains the dominant sponsor supporting the requisite technological developments. Chakrabarti’s suborbital rocket flights were made possible through NASA funding, as was the bulk of recent progress in high-performance coronagraphs for space telescopes. Project Blue itself is largely based on the work of two scientists at NASA’s Ames Research Center in California, Ruslan Belikov and Eduardo Bendek. Although not formally affiliated with Project Blue, in recent years they have co-authored numerous papers detailing the unique opportunities the Alpha Centauri system holds for a modest planet-imaging space telescope. One might wonder, then, why funding from outside is needed at all.
One reason is that NASA has already considered and rejected something much like Project Blue—a 2014 proposal from Belikov and Bendek for a slightly more sophisticated Centauri-focused telescope that would have cost no more than $175 million. At NASA, Bendek says, a “high-risk, high-return single target [mission] with some required technology development doesn’t have an obvious niche.” To many, $175 million seems a prohibitively high price to pay for a mission that promises to investigate only two stars out of the billions in our galaxy alone.
For the private sector the niche is more obvious, although no one is likely to make a fortune finding alien Earths anytime soon. “Project Blue, like all the missions BoldlyGo supports, exists to accelerate the pace of discovery,” Morse says. “We are trying to bring alternate resources to bear to increase the flight rate of new technologies in space. NASA is really interested in seeing its investments pay off, and so we’re here to try to make that happen as soon as possible. We all know we need to get a [high-performance] coronagraph in space.”
There is, of course, no guarantee that Project Blue will reach orbit, operate as planned or find any planets. It could be derailed by lack of funding, or by a malfunctioning rocket or onboard instrument. Or by nature itself: there is a chance that Alpha Centauri’s stars are surrounded by significantly more light-scattering dust than our own Sun, which could prevent a small telescope from seeing any planets. Or there may simply be no planets there to see.
Such worries should not stop the search, some researchers say. “This is science, so null results about our nearest neighboring Sun-like stars are just as valuable as positive ones, although they don’t generate a press release,” says Jared Males, an astronomer at the University of Arizona who is working on image-processing algorithms for Project Blue. “And the coronagraph technology this would test will help us plan for future missions, the huge space telescopes we want to launch decades from now. Even if we don’t find planets around Alpha Centauri, looking for them is going to give us the experience we need to find more around other nearby stars.”
The situation, Bendek and Belikov say, is similar to what the Kepler mission faced. That mission languished for 20 years as a perennial NASA also-ran, being proposed and rejected several times before finally launching in 2009. “People were criticizing Kepler constantly, saying it wouldn’t work,” Bendek says. “But in the end, if they had been more supportive, the mission might have flown earlier.” Today, its transformative results have almost single-handedly made the study of planets orbiting other stars the hottest subfield of astronomy, and have become a linchpin in NASA’s multibillion-dollar plans for a variety of future missions.
“Every revolutionary idea evokes three stages of reaction,” Belikov says, paraphrasing a famous quote from the late science fiction author Arthur C. Clarke. “The first stage is, ‘This is just crazy and will never work.’ The second stage is, ‘Maybe it will work, but it’s not worth doing.’ And the third stage is, ‘I thought this was a great idea all along.’ Kepler has now passed through these three stages. I believe our idea is now on stage two. We hope to get to three.”