Light of the Stars by Adam Frank

Author:Adam Frank
Language: eng
Format: epub
Publisher: W. W. Norton & Company
Published: 2018-08-07T16:00:00+00:00

THE PATHS TO AN ANSWER

Frank Drake and Carl Sagan’s very public discussions about exo-civilizations established the scientific basis for the search for extraterrestrial intelligence, or SETI. But the search itself would require a new generation of scientists. Chief among their number was Jill Tarter.

Like Drake, Tarter began her scientific training at Cornell, in the engineering physics program. But by the time she completed graduate school at the University of California, Berkeley, she’d decided to focus her work on SETI.3 Over a long and distinguished career, Tarter carried out observational programs at radio observatories across the world, served as project scientist for NASA’s SETI program, and was given the Bernard M. Oliver Chair at the SETI Institute.4 She has seen firsthand how the question of exo-civilizations and the question of exoplanets converged.

In the 1970s, Tarter’s dedication to SETI took her to a series of meetings where questions of precision and planet detection were first taken on in earnest. “Technology for finding planets just didn’t exist back in the early 1970s,” she says. “That means astronomers needed to get together and figure out exactly what the barriers were and how we could beat them.”5 With this goal in mind, in 1975 a workshop was organized at NASA’s Ames Research Center in San Jose, at which the general problem of SETI technologies was first laid out. This workshop focused on search strategies for signals from exo-civilizations, but the attendees agreed that the factors in the Drake equation needed to be explored on their own as well. The most important of these sub-questions was the fraction of stars with planets and the fraction of planets in the habitable zone.6

“The original workshop led to two others that focused explicitly on planet-hunting methods,” Tarter told me in an interview. “There was a meeting at [Ames] in 1978. This was the first time the different methods of planet hunting were drilled down into to see which one had the highest chance of success.”

Records from that meeting show that most of the discussion focused on astrometric sky mapping, the approach that See used. Searches based on detecting reflex motions were discussed in detail, too. Direct detection—actually seeing the light from a planet—was also on the table.7 But the transit method, based on the dimming of starlight due to a passing planet, didn’t even make it into the report. The future would show the irony of this exclusion.

Though the problems with all the methods were acknowledged to be vast, the report ended on a positive note. “The prospects of increasing our confidence concerning the frequency and distribution of other planetary systems are good,” the authors concluded.8 Later, another SETI-inspired NASA workshop was held at the University of Maryland to explore technical details in more detail.

“People came away from that [second] meeting with a sense of what was possible,” Tarter told me. “The reflex motion approach was seen as particularly promising if the technology could be hammered out. I think a lot of folks were really excited.”9

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