The Science behind The Orion Plan
I got the idea for this novel back in 1999 when I edited a special issue of Scientific American that focused on space exploration. One of the articles in that issue was titled, “Interstellar Spaceflight: Can We Travel to Other Stars?” Written by science journalist Timothy Ferris, the article argued that traversing the vast distances between stars was so inherently difficult that any spacefaring civilization would be unlikely to send large starships across the galaxy. It would make more sense to launch small automated probes instead, because they would require so much less fuel to complete their interstellar journeys.
The article inspired me: I could easily imagine a small probe from a distant star system landing in someone’s backyard. Better yet, I could imagine it following a set of preprogrammed tasks, using the raw materials at its landing site to establish a foothold on our world. This kind of probe could swiftly build all the machines it would need for exploring the planet -- or colonizing it.
As I wrote the novel I tried to weave some real space science into the story. A group of Cornell astronomers (including Frank Drake and Carl Sagan) really did send a message across the Milky Way in 1974 using the Arecibo radio dish. And the novel’s description of Martian microfossils is based on the investigation of ALH84001, the meteorite that became famous in 1996 as scientists debated whether it held fossils of Martian microbes. My opinion on this subject is similar to Sarah Pooley’s: as we continue to explore planets in our star system and others, we’re bound to discover evidence of extraterrestrial life.
But what are the odds of finding intelligent life out there? On Earth, it took billions of years for microbes to evolve into complex multicellular organisms, and only in the past century has one species become capable of building powerful rockets and radio transmitters. We simply don’t know how evolution would progress on other planets, or how long an extraterrestrial civilization would be likely to survive. Still, some scientists are worried about intelligent aliens; in February 2015 a group of prominent space experts warned against trying to find extraterrestrials by transmitting more signals similar to the Arecibo message. As the group’s statement noted, “It is impossible to predict whether extraterrestrial intelligence will be benign or hostile.”
UPDATE: Alien hunters now have a new target for their telescopes. The intriguing star system was identified by the Kepler Space Telescope, the NASA probe that has delighted astronomers by proving that our galaxy is packed with planets. From 2009 to 2013 Kepler monitored more than 100,000 stars to see if any orbiting planets passed in front of them -- that is, directly between the star and the telescope. This event, called a planetary transit, blocks a small fraction of the star’s light every time it occurs and enables scientists to estimate the size of the planet and its orbit.
Researchers are still analyzing Kepler’s observations, but they’ve already confirmed the presence of more than a thousand distant planets, many of which are roughly the same size as Earth. What’s more, about a dozen of the Earthlike planets orbit within their stars’ habitable zones, which are also called “Goldilocks zones” because the orbits are situated neither too close to their stars nor too far away. In all likelihood, the surface temperatures on those worlds are just right for liquid water -- and maybe life.
In October 2015, though, a team of astronomers released an even more surprising report that raised the hopes of UFO watchers everywhere. The study focused on Kepler’s observations of an F-type star -- larger and hotter than our sun, which is G-type -- located about 1,480 light-years from Earth. (Unfortunately, the star lacks a good science-fiction name, such as Vega or Rigel; instead, it has the rather unexciting designation KIC 8462852.) Over the four years of Kepler’s mission, this star dimmed dramatically several times. The intensity of the starlight reaching the telescope plunged 15 percent at one point and 22 percent at another.
These stellar brownouts were far more severe than the dimming caused by a typical planetary transit. In other star systems monitored by Kepler, even the biggest planets blocked only 1 percent of the starlight. Still more puzzling, KIC 8462852 darkened at odd, unpredictable intervals -- sometimes after hundreds of days, other times after just a few weeks -- and not in the regular, clockwork pattern you’d expect to see if one or more large planets were obstructing the light.
The team of astronomers, led by Tabetha Boyajian of Yale University, tried to determine what caused the strange dimming. They considered the possibility that the star is surrounded by a protoplanetary disk, a vast, clumpy cloud of gas and dust that could block the star’s light in an irregular pattern. Such disks, though, are usually seen around young stars with planets still coalescing from the dust, and all the astronomical evidence indicates that KIC 8462852 is much older. Furthermore, observations of the star by another spacecraft showed no sign of the infrared radiation that would be emitted by the warm dust grains.
A more likely explanation, the astronomers concluded, was that a comet orbiting the star had disintegrated into a huge swarm of fragments that obstructed the star’s light as they zipped past it. The comet might’ve careened too close to the star, allowing powerful gravitational forces to tear it apart. Because the fragments would tend to disperse along the comet’s path, the debris would swing past KIC 8462852 in an irregular pattern and come near enough to the star to block a large portion of its light. But other scientists questioned the hypothesis because it relied on a pretty remarkable coincidence: that the Kepler telescope happened to observe the star system shortly after the cometary cataclysm.
Soon another group of astronomers proposed a more radical hypothesis. A team led by Jason Wright of Penn State University had already studied whether Kepler’s data could provide clues to aid the search for extraterrestrial intelligence. In 1960 physicist Freeman Dyson theorized that an advanced alien civilization in a distant star system would be likely to build tremendous power-collecting structures around its star to capture as much of its energy as possible. These megastructures might consist of swarms of giant photoelectric panels, each thousands of miles across, or even a vast shell -- the so-called Dyson Sphere -- that complete encloses the star.
A Dyson Sphere would absorb all the star’s light and reradiate it as infrared emissions, but a swarm of megastructures would block the starlight in a highly irregular pattern that would depend on their size and shape and orbits. According to the research paper submitted by Wright’s team, KIC 8462852 has “all of the hallmarks of a Dyson swarm.”
The paper dutifully warned that researchers should first investigate all the possible natural causes of the strange dimming -- a stream of comet fragments, a dust cloud arising from a planetary collision, and so on -- before “invoking alien engineering to explain an anomalous astrophysical phenomenon.” That warning went unheeded, though, after the news hit the Internet. Stephen Colbert brought up the subject on his late-night talk show, discussing alien megastructures with Neil DeGrasse Tyson, director of the Hayden Planetarium. Colbert displayed a picture of Ringworld, the megastructure imagined in Larry Niven’s 1970 science-fiction novel of that name, but Tyson was unconvinced. “Just because you don’t understand what you’re looking at,” he told Colbert, “does not mean it’s aliens.”
Still, scientists are taking the megastructure hypothesis seriously because they can conduct further studies to test the idea. One such test is to look for other signs of intelligent life in the star system. At the Allen Telescope Array in California, researchers have already pointed their radio dishes at KIC 8462852 to listen for signals transmitted by extraterrestrials almost 1,500 years ago. Because the star is so far away, though, any radio signals that reach Earth would be vanishingly faint. And it’s very possible than an advanced alien civilization would have better ways to communicate than using the wavelengths that our radio telescopes are scanning.
A more definitive answer could come from follow-up observations of the star by ground-based telescopes. Astronomers will monitor the star’s light over the next few years and measure the duration and scale of any future dimming episodes. Better yet, the researchers will make detailed spectroscopic observations the next time the star goes dark, and that will tell them a lot more about what’s blocking the light. The results may bolster the comet hypothesis or perhaps encourage researchers to come up with an entirely new theory.
Or they might find more signs of megastructures. Carl Sagan, the astronomer and science popularizer who often speculated about extraterrestrial intelligence, was famous for saying, “Extraordinary claims require extraordinary evidence.” As of now, the evidence for an alien civilization at KIC 8462852 falls far short of that standard. But it could be a start.