The Glare of Other Suns
An inside look at how astronomers
are searching for extrasolar planets
by Apurva Narechania
The main road on Palomar Mountain ends at a cottage called the Monastery. The Monastery houses sleeping astronomers during the day so they can look into the sky at night. Opening a Monastery blackout shade in midday is like emerging from a matinée. The light of Southern California hurts when training to bear the night.
At around 4 pm on a clear day in December, I rolled out of bed to eat an early dinner prepared by Dipali Crosse, an earnest woman who makes tasty food from the kind of enormous boxes and cans that weigh down the shelves at Costco. Her food is fit for lumberjacks. This is our one good meal of the day. At the oak table, astronomers are already sitting shoulder to shoulder, some chairs angled around inconvenient corners. The Monastery has 12 rooms. On a normal observing run, only a few are occupied. But this week, the place is full. A few even had to shack up at the reservation casino a couple thousand feet down Palomar Mountain. Everyone is in town to see planets. Around stars hundreds of light years away, we now know there are other worlds. But they are impossibly faint, ghosts around the already dim suns that sustain them. On this trip, the light of those stars will be collected and then pared to find the planets in their orbit.
I had first seen the instrument that does the paring at Ben Oppenheimer’s lab at the American Museum of Natural History (I also work at the AMNH as a biologist in the Genomics Department). Oppenheimer is an astrophysicist and his is one of only three ground-based systems designed to visualize extrasolar planets. With its cover off nearly 19 optical surfaces sat exposed, each beaming light to another, and ultimately to a coronograph, a device that functions as an occulter, and is at the heart of any astronomical instrument designed to see things other than stars. Oppenheimer and his colleagues have been working on this instrument for nearly six years. Dubbed Project 1640, the technology uses adaptive optics to calm the distortions inflicted by atmospheric turbulence, and speckle suppression to dampen the residual diffractive light that remains from the star even after it has been occulted. Twentythree computers automate the synergy of nearly 4,000 movable parts. On a five night observing run on the 200-inch Hale telescope—the largest at Palomar and one of the largest in the world—the detector will collect 500GB of data. But most of the data, most of the light, is useless. The instrument must cut through the glare of the nighttime sky to image shy planets. Light from a star saturates its satellites. The starlight itself is extraneous, annoying even. “Once you’ve taken the best picture your technology will allow,” said Oppenheimer, “you have to delete it.” One photon in ten million comes from the world Oppenheimer most wants to see. It’s like staring into the light of a thousand suns or searching for Venus at noon. Oppenheimer deletes his way to clarity.
We end dinner with obscene amounts of coffee, and head to the telescope at dusk. Sasha Hinkley, a postdoc in astrophysics at Caltech and one of Oppenheimer’s former students, is already there, suspended from the end of the telescope in the Cassegrain cage. The cage is a metal enclosure that cradles the fivemeter mirror, forming a giant cup with access to the Hale’s key optics and Project 1640’s instrument. The telescope dwarfs the cage. It rises nearly 13 stories wrapped in a white dome of precious steel borrowed from the industrial machine of WWII America. On the outside about three quarters of the way up, a catwalk skirts the dome and moves as the telescope slews so that astronomers catching a quick smoke might see the lights of Temecula give way to the steady glow of LA County without lifting a foot. The dome is otherworldly whether you’re in it, on it, or looking at it in full moonlight as I did on my first night. Against the dark sky it stands in blanched relief, a functional monument, every part of its interior and exterior curvature accessible and working. Climbing around the telescope, I realized how reassuring corners are. There are no right angles at Palomar. The dome, the mirror, the ingenuity of out-of-the-box people past and present: it’s a giant bowl of light and thought.
I climbed into the cage with Hinkley a fraction of a second after being invited. The telescope was parked, its mirror facing straight up and its body at a right angle to the ground. We were resting on our backs against the cage’s metal, suspended a dozen feet above the ground. Around us in the semi-darkness, cables spilled out of instruments like vines from a metal canopy. Almost immediately above us, the primary mirror lies in its steel bed and the telescope extends as if from our bellies, hundreds of feet up. The mirror is a monolithic piece of glass polished to near flatness, never deviating more than two millionths of an inch. It pivots on a horseshoe mount and glides along oil pads so frictionless that a 1.5 horsepower motor turns its vast bulk. If you’re alone in the dome at night while the telescope slews, it can feel like sharing a cave with a careful giant. Though the Hale telescope has been called the Big Eye, nobody looks directly at the light it collects. A few stories up, towards the crowning secondary mirror, there is a snug, one-man compartment with controls like the cockpit of an old fighter. Its single leather seat is cracked and the spongy cushion cratered. Astronomers used to sit there alone, at prime focus, looking into the galaxy though an eyepiece. Now the Big Eye directs all its light to the instruments that hang above us, open, with their delicate optics exposed. After an hour against the cage, its pattern was etched into our skin even through sweaters and jackets.
Hinkley was trying to focus the instrument using an artificial white light source, moving mirrors and lenses back and forth a few microns at a time. He would tighten a bolt with a twenty-degree turn of an Allen wrench and Oppenheimer would yell at him for going the wrong way or not going far enough. “You ever try to put a Christmas tree up with your wife?” asked Hinkley. His voice went up a register. “‘Rotate it’, she says. ‘Which way? Clockwise. No, wait, counter-clockwise. Don’t put that ornament there! What are you doing?’ ” A wrench in his mouth and another in his hands, he said, “Well this is kind of like that.” The work put the notion of manual focus in entirely new perspective. Modern astronomy is as much about instrumentation as observation, as much an engineer’s field as a scientist’s. “In our engineering, we do things just well enough. Out here things are never going to be perfect,” said Oppenheimer. Observational astronomers are mechanics. No one else could know how to fix their singular machines. “Ben, do you want to come out here and take a look?” asked Hinkley. “In astronomy we have to build this stuff from scratch.”
Oppenheimer joined us. He found a tight spot and squatted in a pile of cable that had collected in the cage. The adaptive optics system alone has nearly 600 pounds of the stuff, snaking around your ankles, coiled against most of the walls. “Cable management if done properly can save you many days of sitting on your ass undoing other people’s knots,” said Oppenheimer, twisting a nut. “I think that should do it. Let’s go check.” As we climbed down the ladder to head into the control room, he caught sight of his knuckles. They were bleeding. In the dry mountain air, most people slough their skin and shrivel, but Oppenheimer, his hands constantly in tight spaces threading metal edges, bleeds. “You bleed into these things. You put your life into them. Look at my knuckle. I don’t know how that happened.”
51 Pegasi B was the first exoplanet discovered around a main sequence star. Before its announcement, exoplanetary science was an astronomical backwater. Cosmology, with its emphasis on the origins of the universe, its boundaries and the constancy of its physical laws, still dominated astrophysical research. 51 Pegasi B brought exoplanets into focus. It’s enormous, nearly 150 times the size of the Earth, about half the size of Jupiter. But unlike Jupiter, 51 Pegasi B orbits its star at distances that would set your hair on fire. Imagine a planet of that size whipping around the sun inside the orbit of Mercury. 51 Pegasi B screams around its star completing one full orbit in four careening days. It’s a Hot Jupiter: a gaseous planet with a scalding surface. Its period of rotation mirrors its period of revolution, so only one side faces its star, an arrangement astronomers call tidal locking or synchronous rotation. Some artists’ renditions situate the planet at the flaring edge of its star’s corona: a giant world of baked gas unfurling in its speed. Prior to its discovery, most theorists thought that gaseous planets could exist only in the farthest orbits of stars. 51 Pegasi B probably did form in the further reaches, but then migrated inward, stopping just short of falling into its sun. In 1995, when 51 Pegasi B was discovered, the only planets known were those in our solar system, where gas giants operate in distant orbits. 51 Pegasi B turned planetary science on its head.
The last ten years of exoplanetary study have outstripped any narrative. There are planets believed to be the consistency of Styrofoam, ocean worlds with nitrogenous atmospheres, carbonaceous planets that might be studded with diamonds. Planets that circle two suns, and rogue planets presumably flung from their parent stars to wander the galaxy alone. And we are on the cusp of detecting planets that sit in their star’s habitable zone where liquid water and a shielding atmosphere coexist to perhaps nest extraterrestrial organics. Science like this buries science fiction. When 51 Pegasi B was first discovered, it inspired a renewed wave of thinking about our place in the universe. Exoplanetary science was clearly no longer the soft pocket of astrophysics, filled with careless futurists and their philosophers. It was real. If there are planets and we can detect these planets, how many are there and are there others with Earth’s chemistry? The notion of life elsewhere went from whimsy to hypothesis. SETI, the Search for Extraterrestrial Intelligence, garnered a bit more cachet. NASA formalized its Astrobiology program. Astronomers dedicated more telescope time to the search for giant planets. A Time magazine cover ran with the headline, “Is Anybody Out There?” For science and astronomy magazines, the question is a trope that never fails to pique its core, warp-powered audience. But because there was finally data, young scientists were listening. Oppenheimer’s early work as a graduate student at Caltech was juiced by these discoveries. 51 Pegasi B was remarkable not because it existed, but because it was so exotic, so unexpected in its size, composition, and proximity to its star. Theorists build models on what they know, but space is vast and the configurations of things unseen are manifold. We just don’t know what to expect. So why not expect life to be out there? And why not look for it?
51 Pegasi B is located only fifty-one light years from Earth, a next-door neighbor. In comparison, the Milky Way is 100,000 light years in diameter. The light we now see from its opposite edge was first emitted as modern humans were leaving Africa. That’s old light, but at least we have a chance to see it. The universe is large on another scale altogether. Light from events in its past may never reach us. Astronomers call this the past horizon, a limit on the most distant objects we can see. In the same way, light from us may never reach its outer rim. This is called the future horizon. Bound by horizons past and future, we occupy a corner of the universe we can observe and affect, and there are things about it we can never know. But it’s this sense of vastness that is most compelling to exoplanetary scientists. The universe is likely filled with as many if not more planets than stars. And because planets are cool and exist at various distances from their suns, their chemistries are more complex. If you know a star’s mass and composition, you can predict its lifespan and its life’s work. Planets are the dark horses of the universe. Its art resides within them. The question is, just how creative has the universe been?
I first met Ben Oppenheimer at his office in AMNH. He sat at a neat desk in front of a wall bathed in bluish-purple light, as if peeking out from a nebula. I introduced myself as a fellow scientist completely naïve to astronomy, but fascinated by early life on this planet and the possibility of life on others. Try making this admission in an astrophysicist’s office. I knew that Oppenheimer was a new breed of astrophysicist who no longer thinks exoplanetary science and habitability is fantasy. But it’s still hard to shake the self-consciousness inherent in legitimizing your Sci-Fi childhood. I timidly suggested that any article on his work should deal with the search for habitable planets. I must have sounded apologetic because he looked amused. “I think the issue of life is, in the end, where this is all going. It has to. I think people want to know. If there is an earthlike planet out there, what is it like?” His eyes flickered beneath stylishly framed glasses. I asked him if we could ever hope to perceive, let alone conceive, life as we don’t know it. “It’s important to keep the parameter space for whatever you’re doing as open as you can,” he said. Translation: I have no idea, but be openminded and prepared. “I think this is one of the deepest philosophical questions people have had for ages. Is there anything else out there?”
But what do you look for? How do you start? At a glance, through any telescope, 51 Pegasi B and its star, 51 Pegasi are a single body. The planet is in so close an orbit that its own light is blanched. But you can still infer its existence. Almost every exoplanet discovered so far has been detected through inference. 51 Pegasi B exerts a gravitational effect on 51 Pegasi causing the star to either inch toward or away from an observer. This quiver is detectable as shifts in the color of the star’s light. The effect is Doppler in nature. An approaching object either shines or sounds with quickening frequency. That same object’s frequency abates as it recedes. The technique is called radial velocity: the change in velocity of the star given its planet’s gravitational influence. Jupiter causes a 12.7 m/s change in the sun’s radial velocity. 51 Pegasi B clocked in at 70 m/s. Earth causes a 9 cm change, a number that puts into perspective our galactic insignificance.
But Oppenheimer believes that inference is not enough. The problem with inferential techniques like radial velocity is that they are information poor. You can get a sense of the mass of a planet and its orbit, but if you can’t see it, if you can’t gather any light from it, you are blind to its true nature. Still, inferential techniques are mature and proven. Radial velocity is only one in an arsenal of inferential methods. The fabulously successful Kepler mission has uncovered more planets in the last year than had ever been detected before. So far, 2300 planet candidates have accumulated in its three years of operation. Kepler is a space-based telescope tasked with staring at the same set of 100,000 stars for seven and a half years. If a solar system is arrayed edgewise with respect to Kepler, any planets that cross in front of the system’s star would register as diminished starlight. Like the radial velocity technique, the change is beyond subtle. A typical planet might reduce the light of its star by 1 to 10 parts in a million. Signals are so faint, and the opportunities for observation so erratic and evanescent, even firm observations are never infallible. An Earth-like planet would produce this weak signature once a year. Kepler requires at least three such passes before elevating the observation to a planet candidate. If a given star’s dimming is due to a planet, the change will be periodic, revealing size and trajectory. But many of the finer details of the planet remain a mystery.
Figure 1: Three large planets (b, d, and c) around the star HR 8799. (Science. November 28th 2008. Volume 322, Page 1348.)
Exactly thirteen years after the existence of 51 Pegasi B was published, a new technique called direct observation yielded its first success: three large planets around the star HR 8799. Direct observation dispenses with inferential data. Instead, light from planets is separated from the star and concentrated with long exposures. The known system is shown in Figure 1 (to the right).
In this image, the planets are nearly 100,000 times fainter than the star. Without starlight suppression, the entire frame would render as a block of impenetrable light. The remnants of the star are visible as a collection of iridescent speckles, and around this ball of muted light orbit three small, red dots: HR 8799 b, c and d. Speckles are such a notorious problem in optics of this kind that a whole subfield has been spawned to invent ways to contain them. Fortunately, HR8799 has a giant solar system with distant planets that aren’t consumed by the speckles. Our own system would sit squarely within the cluster. Neptune is about as far out as HR8799 d. The most distant planet in the HR 8799 system is 68 astronomical units away from its star, or 68 times the distance of the Earth from our Sun. It takes 450 years to complete one orbit.
HR8799 is a young star. It’s so young that its visible planets are still hot and generate their own light. Earth-based direct observation can only detect hot planets. The imaging technology is not yet capable of detecting reflected light. It’s too faint. But a spacebased telescope could do the job. In May of 2002 NASA funded a feasibility study for the Terrestrial Planet Finder (TPF), a proposed orbital telescope devoted to planetary imaging and the cancellation of starlight. The TPF’s angular resolution would make detecting a Jupiter-like planet a cinch and an Earthsized planet a genuine possibility. In 2004, the TPF’s architecture was approved for construction at a cost that engineers estimated at $10 billion. By 2009, after the dramatic depths of the recession had worked its way through the budget, NASA’s share had shriveled and the TPF’s completed schematics were bound and shelved, a worked but unrealized solution. Oppenheimer has no patience for the government’s misallocation. “NASA’s budget in the scheme of things is ridiculous. It’s like a drop in the bucket. We could choose to do so much more, but we don’t,” said Oppenheimer. “If you want to understand the Earth, you need something to compare it to.”
HR8799’s currently visible planets could never sustain Earth-type life. But rocky worlds in its habitable zone may be buried in the morass of speckles. While transiting and radial velocity excel at the detection of Hot Jupiters and planetary bodies close in on their stars, ground-based direct observation is limited to the detection of gas giants at glacial distances. Coronography has succeeded in making the light of distant planets accessible, but starlight is a pesky thing. It diffracts around the optical stop, it leaves ghosts of its deleted self. The speckles can be dimmed but never removed. The exoplanetary sweet spot, the habitable zone, a narrow ring around each star, is ironically the most elusive band for detection of any kind.
The technical challenge is immense. Project 1640 consists of four homegrown instruments that relay light from the sky to a computer screen. The optics are so complex that only 10% of the non-occulted, impinging light survives the process. First, the adaptive optics system compensates for the atmosphere. The coronograph then tempers the target star’s light. An integral field spectrograph, which Oppenheimer simply calls the science camera, records 30 images of the star across 30 different colors simultaneously. A calibration wavefront sensor (CAL) measures and compensates for the defects in the optics. Images from the science camera are stacked, one slice per color. Oppenheimer calls this 3D image The Cube. It’s not three-dimensional in space. The image of the star is flat. Here, depth is devoted to color. The location of a speckle is dependent on the color observed. If you trace a single speckle through the cube, you’ll notice that it radiates out from the star’s center. The cube is the star’s pop-up book, telling its story in three dimensions with slices through the electromagnetic spectrum. The images are beautiful when animated, as if the star were a multi-chromatic geyser of its own occulted remnants. Planets are points of light that drill through the cube, motionless through every section as the speckles scatter.
Of all the instruments currently used at the Hale telescope, project 1640 is the most complex. In all, the project has one hundred nights of observing time. When the sun goes down, a clock starts ticking in Oppenheimer’s head. If it rains, if it’s cloudy, if the seeing is lost in swirls of misbehaving air, he goes home with nothing. There are no allowances for bad luck. The Monastery has a guest book where scientists and visitors can formalize their paeans to Palomar. When Oppenheimer signed this book four years ago, he did not mince his ambition with customary homage. Instead he wrote a declaration. “June 24th, 2008. Project 1640 has arrived from NYC. We shall see whether it works in short order.”
Three and a half years later, Tom Lockhart was sitting on the toilet seat in the control room’s bathroom. The temperature in the dome had dipped below freezing, unusually cold even for December on the mountain. Lockhart designs and runs the software controlling the CAL system. He wore a hat with earflaps and was warming a motherboard against the radiant coils of an old heater. “I don’t know. The thing just started beeping,” he said. Computer hardware fails when it’s hot. Everyone knows that. But the motherboard in the CAL started talking to Lockhart when it got too cold. “It slowed to a fraction of its normal speed and then told me it was shutting itself off. You ever hear of anything like that?”
The telescope was pointed at HR 8799. Oppenheimer wanted to see whether the new instrument could pick up known planets. “Can you people please clam down? Where’s Tom?” Oppenheimer asked.
“He’s in the bathroom having a good time with the CAL’s processor,” Gautam Vasisht said. Vasisht is the CAL’s hardware designer. He and Oppenheimer shared an office when they were graduate students at Caltech. Vasisht is the small, ironic subtext to Oppenheimer’s volubility. “So much for the romance of astronomy.”
“I feel like I’m doing the same thing over and over again. Like I’m in some kind of nightmare,” Oppenheimer said. Trouble with the CAL’s processor meant less time on sky. “In a way, it’s good there’s bad seeing.” The stars were translucent behind a high, thin sheet of clouds. “Where the fuck is Tom? Seriously. Is the CAL going to work? It might clear any second.”
The room was filled with physicists. Mike Shao, honored with the 2010 Michelson prize for his pioneering work on ground and space based interferometers, asked if there was a resistor lying around. “If we plug in a resistor and put it directly on the computer’s enclosure, would that heat it up enough?”
Shao’s suggestion was like asking an astronaut whether duct tape could hold together a splintering spacecraft (which worked for Apollo 13!). After years of engineering precision starlight control, in unanticipated cold, the resistor was the kind of kluge you have to dig deep for: high school physics rounding out the rough edges on Palomar Mountain.
“There might be something downstairs. Hold on,” said Kajsa Peffer, one of the telescope operators.
Lockhart stood up, turned off the bathroom heater, and closed the door behind him. Satisfied with the roasting he gave the CAL’s motherboard, he went into the dome to reinstall it. He took with him some duct tape and the resistor Kajsa had dug up from the spare parts room. Lockhart strapped the resistor to the instrument, and turned off the computer’s cooling fans, so the work of imaging other worlds could proceed
“We’ve tried to image this system eight times and the conditions have been bad every time,” said Oppenheimer. “Now the conditions are bad and all the instruments are screwed up. It’s like the aliens are trying to hide their planet from us.”
“Imaging exoplanets: an exercise in fucking futility,” said Vasisht.
“Seriously man. I hate this fucking star. We haven’t recorded a single science frame tonight. This star hates this project. Kajsa, how long can we stay on this piece of shit?” asked Oppenheimer of the telescope’s operator.
“Two more hours? Oh god. You people need to calm down.”
When you can get it, light from a planet is a rich source of information. A few collected photons can betray an entire atmosphere’s chemistry. Chemical species absorb particular frequencies of light leading to dips in reflectance along certain points in the spectrum. In 1961, James Lovelock, an independent scientist and inventor, was contracted by NASA to determine what could be seen from a planet’s light, from these spectra. Lovelock reasoned that if a planet were alive, its atmosphere would contain highly reactive compounds—oxygen, methane, hydrogen— at high concentrations despite their tendency to react with one another. From afar, a spectrum of our planet’s atmosphere would betray chemical disequilibrium. Oxygen and ozone cooccur with methane. Water vapor lubes the mix. On a dead planet, molecular oxygen and fully reduced carbon (like methane) would be unlikely to co-exist. Life keeps these biosignatures at high concentrations as raw material for our fundamental processes: respiration and growth.
We only know of one planet with life. With this in mind, Carl Sagan devised an experiment to peek at Earth from space. In the early 1990s, as the Galileo spacecraft swung around Earth in a gravitational shot towards Jupiter, Sagan turned its camera back towards our planet. In the paper describing this effort (Nature 365, 715–721, 21 October 1993), Sagan imagined the Earth was extraterrestrial, deriving “conclusions from Galileo data based on first principles alone. He found an “abundance of gaseous oxygen” and “atmospheric methane in extreme thermodynamic disequilibrium.” The spectrum also highlighted a “widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum.” Chlorophyll: plants. Of course, the experiment was a conceit. The light Sagan collected, its luminosity and detail, is a pipe dream given the scraps Oppenheimer collects from other worlds. The question is what would Earth look like if you could only scavenge a few photons? What would it look like well beyond our solar system?
It turns out you can look back at the Earth, as if from deep space, while standing on your roof. Our planet is reflected back to us every night by the moon. During its crescent phase, the moon’s brilliant edge cradles an ashy wisp of the rest of its body. The crescent reflects the Sun while the darker whole reflects the Earth. This phenomenon is known as earthshine: our light returning to us from our moon. Because the moon is an imperfect reflector, the Earth’s light is homogenized, mimicking its appearance from great distances well beyond our solar system, even from neighboring stars. Earthshine is our best guess at what the light from a living, breathing planet might look like when viewed from other parts of the galaxy. Above is a picture of Earth from the moon, our proxy for light years away (Figure 2).
Figure 2: Measuring earthshine as reflected by the Moon is our best guess at what the light from a living, breathing planet might look like. (Redrawn from The Astrophysical Journal, Volume 644, Issue 1, pp. 551–559.)
This is a spectrum. The x-axis plots a narrow section of wavelengths in the visible and near infrared. The y-axis is an index of reflectivity: lower reflectivity at a given wavelength implies an absorbing entity, a molecule cutting into the light. The signatures of life on this planet are coded into the peaks and dips of this graph: the oxygen respired by animals, the carbon dioxide absorbed by plants, the methane emitted from geological activity like volcanoes and biological activity like flatulent cows, the ozone that protects DNA from ultraviolet radiation, the water that supplies electrons for building complex sugars in plants, and the signature of pigments used by the light-harvesting biomolecular machines that energize this planet. A living planet’s vitality informs its chemical constituency and life is dissolved into an atmosphere of its own creation. This thin shell of gas is a message from the planet; light can signal whether it’s alive or dead. Pictures like these are what Oppenheimer and the Project 1640 crew want from faraway worlds. But the spectra will be fingerprints, detailed, distinct. If it exists, life elsewhere will likely be very different, but still optically and chemically accessible.
The CAL’s processor was back up and only one hour remained before HR8799 would set. Now that everything was finally working, the stars hid behind a new set of thin clouds. “Of course that would happen,” Oppenheimer said. “It’s like we can’t win with this crap. Why don’t we do something easy like banking? We’d make a lot more money.”
“In Monopoly, my daughter’s realized that if she’s the banker, she always wins,” Vasisht said.
“If I wanted to make money then I wouldn’t be here,” said Douglass Brenner, a programmer, physicist, and Oppenheimer’s right hand for the last five years. The group refers to him as The Doug. The Doug thinks he looks like Steven Spielberg with long hair. The Doug likes to talk about Peak Oil and signal processing.
Postdocs Justin Crepp, Laurent Pueyo, Sasha Hinkley, and myself were also in the control room, a safe distance from the actual controls. Crepp wrote the software that achieves speckle reduction. It’s a work in progress known as the Justin Program. “At my Caltech reunion all my old classmates had hedge funds,” Vasisht said. “They have a lot more money then me. One of them asked me to invest so I put in a hundred.”
“A hundred what?” The Doug asked.
Pueyo was listening in. “Banking? Well, at least we’re not bored.”
The sky was sealed. Crepp fiddled with the Justin program. Hinkley read papers. Pueyo skyped with his Mom in France about his upcoming wedding in San Francisco. By the time the clouds cleared HR8799 was gone, so the telescope was trained on anther star, FU Ori in the constellation Orion.
Oppenheimer set the instrument to take fiveminute exposures before heading to the catwalk. With every iteration, a woman’s voice would mark data capture. “Image processing complete. Awaiting instructions.” The voice is sultry, receptive, and almost expectant. Oppenheimer had programmed her as a joke. She sounds like HAL’s humanizing mate. But unlike Arthur C. Clarke’s HAL, whose creepy conversation betrays progressive hints of malfunction, the woman’s words are unchanged even as Oppenheimer’s system faults in subtle ways, even as everyone’s head is buried in their hands. At one point earlier in the evening, sometime after the CAL’s hardware had warmed and before its software had failed, Oppenheimer lost his cool. He is intense, but rarely out of control. The night’s failures were too much. “There’s no tomorrow in optical astronomy,” he said. “The rotation of the Earth doesn’t care about your apologies.” He said it to no one in particular. He might as well have said it to himself. Project 1640 is a lose conglomeration of parts that barely fit, and people that fit together almost too well.
At 5am our brains were fried. I looked around and saw the same blank look in everyone’s eyes. Night lunches were strewn about. A Christmas tree was edging off its table. The smell of stale coffee rose from a dozen cups. The long night had removed key modules from our heads. As dawn lightened the sky and bodies felt the abuse of sleepless exhaustion, I could almost hear HAL in my head: “I’ve still got the greatest enthusiasm and confidence in the mission. And I want to help you. But my mind is going. I can feel it.”
The Drake equation looks like this: N = R* × fp × ne × fl × fi × fc × L
Where N is the number of civilizations in the galaxy with which we might communicate. N is directly proportional to R*, the average rate of star formation per year in our galaxy because, presumably, any habitable world will need a parent star. Then there are the whittling terms. What fraction of those stars have planets (fp)? How many of those planets are similar to earth (ne)? What fraction of these demonstrate signatures of life regardless of complexity (fl)? What fraction of the planets with life generate intelligent life, self aware and capable of formulating long, inscrutable equations (fi)? What fraction of planets with such beings communicate the signals of their technology in ways we can detect (fc)? And how long do these civilizations persist before they go extinct (L)? The Drake equation is like a confident man who stands tall before he is cut down to size. There are billions of stars in the galaxy, but successive fractionation can make astronomical numbers seem terrestrial. Frank Drake conceived the equation in 1960 after making the first attempts at detecting radio signals from extraterrestrial civilizations. Shortly thereafter, Drake organized a meeting on the detection of extraterrestrial intelligence, which ultimately seeded SETI. The equation was devised as talking points for an agenda. “I wrote down all the things you needed to know to predict how hard it’s going to be to detect extraterrestrial life.” Drake factorized each hurdle.
Some of the scientists on Project 1640 are shy about this notion of life on other planets. Others won’t shut up about it. If their willingness to speak on the subject were itself a spectrum, Oppenheimer would anchor the forthcoming believers. Mike Shao is far more reticent. When I asked him his thoughts on habitability, I pushed him on the potential momentousness of such a discovery. With a faint grin, he deflected my enthusiasm without being mean or unsupportive. “Yes, finding planets that can support life is a little bit different than finding a normal planet.” Really? A little bit different? Gauthum Vasisht is similarly evasive. “Frankly, I’m more interested in the architecture of planets. Fools like me get excited by any little thing. I guess some people are better at looking at the big picture.” Shao and Vasisht deployed the measured tones of science to diffuse the science fiction. The Doug, a self-anointed skeptic, was less willing to let a journalist run away with the idea of life on other worlds. “Astrobiology is a complete waste of time. The habitable zone is just a way to keep the public interested. There’s so much out there. We really don’t have a clue. I think it’s more bullshit than poetry.” Against the cynic, many of the students stood out in optimistic relief albeit tempered by their first few tastes of fiscal reality. At one point, while in the cage talking to Sasha Hinkley he got into a fit about our nation’s commitment to science. We were in the dark turning Allen wrenches a few millimeters one-way, and a few less back. “Americans spent $500 billion on gambling last year. Do you know how many more candidates we could generate with that kind of cash? It’s a real shame, man.”
Perhaps the most balanced of the astronomers I met was Charles Beichman, the Executive Director of the NASA Exoplanet Science Institute at Caltech. Chas, as he’s known to everyone on Project 1640, has been instrumental to the development of direct observation and isn’t shy about the work’s implications or its difficulties. “Astrobiology is part of the program. Biologists are part of our program. What do we mean by life? How much is specific to Earth, how much is based on universal principles? I’ll bet that life is abundant, but the thing is, I’ll probably never have to make good on that bet.” Beichman illustrated how far he was willing to go by hopping along the Drake equation. “We have an estimate for the number of stars in our galaxy, we know that each star has at least one planet, and we’re starting to get spectra that may nail down the fraction of these that are habitable.” But Beichman won’t touch the later terms. “The search for intelligent life is a search for electrical engineers.” If SETI is successful, we will know of at least one technological civilization capable of communication, but the discovery is not a quantity that can be factored back into the Drake. It’s one instance, one world with no statistical heft. It might be the most important discovery ever, but it would draw a line between two technological civilizations and dispense no clues as to whether the line is just one strand in a larger web.
Oppenheimer believes we have to look for life, simple or otherwise. In a review he wrote detailing the state of direct observation, Oppenheimer concluded with an impassioned mission statement, the kind you don’t see in the scientific literature. “Given the immensely compelling nature of the science involved in detecting places that might host life outside our Solar System, there is no question that, barring the annihilation of Homo sapiens, people will, and in some sense must, conduct such missions. We know how to do them now” (Annual Review of Astronomy and Astrophysics, Volume 47, pages 253–289). The passage is both a goad and an admonition: Get on it! Why haven’t we done it yet? It’s a directive, a call to arms. I’m surprised he got away with it.
Oppenheimer’s personality is often in conflict with the inherent passivity of his craft. Astronomy is almost wholly observational. We are not in conversation with the cosmos, and it is this unidirectional flow of information that makes astronomy our purest and in some ways, most frustrating science. We cannot affect the product. The universe just sort of happens to us. You wait for light and it arrives with a message from the past, long after the source emitted it, perhaps long after the source has died. We have no capacity to affect the universe in any significant way. And because astronomy is so much a science of soaking things in, of waiting for information to come to you, we have built larger and larger telescopes to make sure nothing is missed of the light the universe bathes us in. The reward is deep astronomical vision.
But not yet deep enough. If we want to image other Earths, we need to do it from space. We can’t sift the light the way it needs to be sifted from the ground. The Terrestrial Planet Finder would have at least had a chance. “When you first think of a new idea, it’s like digging in topsoil, but with each technique you end up hitting bedrock,” said Beichman. The bedrock could be the limits of our technology or current understanding, it could be the realization of an engineering nightmare, or it could be political unwillingness. “So you get another shovel and dig somewhere else.” We live in a nation more attuned to our terrestrial messes than our larger place in the cosmos. We’re all about warming ice, warped economies, and war. To a dreamer with the long view on space and time, quotidian upkeep of our planet is both an afterthought and a black hole—so minor in the grand scheme but a sink for all of our collective energy.
Shortly before our trip to Palomar, Oppenheimer and I had lunch around the corner from the museum. While we were walking back, the sky opened over the Upper West Side and it began to pour. Stuck on Columbus Avenue, we ducked under an awning and stood around for a bit, waiting for the worst of it to pass. “Do you like rain?” Oppenheimer asked. We had been walking in silence for a few seconds, and I was asking all the questions, so I was a bit startled. I told him I didn’t mind as long as I wasn’t caught without my umbrella. His eyes lit up. “I prefer the rain,” he replied. “The sun can be so brilliant it blocks all the color.” I had never thought of color in this way. Everything seems so much more radiant in the sun. But to Oppenheimer the sun has a dulling effect. “I can see so much more clearly when it isn’t out.”
Whether it’s this planet or one 50 light years away, Oppenheimer quenches the glare of suns. Our exchange got me to thinking more about coronography. Project 1640 blocks starlight using a physical occulter and digital subtraction. But there are more fantastic, space-based notions as well. Mike Shao told me that when you build a one of a kind machine in space, “the cost is what the person writing the check is willing to pay.” So imagine a space-based telescope trained on a star whose planets are thought to be rocky and in close orbit, like our own. Now imagine that this telescope is equipped with its own shade, a giant piece of circular material two football fields in diameter that unfurls between the star and the telescope’s aperture. The edges of the shade gently oscillate around its center, the projection of a sunflower in interstellar space (Nature 2006 442(7098): 51–53). The star shade blocks a sun’s light before it enters the telescope. All that remains are the tiny specks around it, now in relief, amplified.
The dream is of amplitude. In both the astronomical and figurative sense, amplitude is what we want from these great eyes to the sky. We want to brighten the dim and we want to see with greater depth planets within the horizons of our perception. In one of our earliest conversations, Oppenheimer told me that when he sits down to think, all he has is the light. This insight is so clean and exhilarating. Light rains into a million backyard telescopes and a handful of engineering monuments. The universe transmits information in tight little beams. There’s nothing else. Large mirrors collect this information with great acuity. Large shades block the most obvious rays. But in the end all we want is the light from what we know must be there—hope is there—but can’t yet see.