SETI: Narrowing the Candidatess

Environmental & Science Education, STEM, Cosmos, Astronomy, Earth & Space Sciences

Ed Hessler

"Because that's where the money is."--reply of bank robber by Willie Sutton on why he robbed banks.

I was reminded of this quote when I read Alexandra Witze's essay in the British science journal Nature about scientists searching who search for "extraterrestrial life should narrow their hunt to stars and planetary systems that have an occasional view of Earth as it passes in front of the Sun." (my emphais)

There are about 2000 candidates that have been "pinpointed" by astronomers "from where, in the not-too-distant past or future Earth can occasionally be detected transiting across the face of the Sun." They have "the cosmic front seat to see us," said Lisa Kaltenegger of Cornell University in Ithaca, New York, "who led the analysis" reported in Nature. 

Witze's essay includes a bar graph showing the number of stars that have been swept by human-made radio waves, the number in the right position to have spotted Earth in the past 5000 years, and additional stars that will have a view of the planet in the next 5000 years. 

The purpose of the study was to identify "which stars have 'a better-than-average shot of discovering and characterizing the Earth,' said Sofia Sheikh" who works at the Berkeley SETI Research
Center in California.  Here is a video (5m 08s) by Sophia Sheikh about new strategies for SETI made when she was nearing the end of her Ph.D. at Pennsylvania State University.

Witze notes that the method used "is the same one that Earth-bound astronomers have used to discover thousands of exoplanets: detecting the light of a distant star dimming slightly and regularly, as an orbiting planet passes across its face."

Read Witze's reporting here where you can read the abstract of the paper on which it is based. The rest of the paper is behind a subscription/paywall. Witze's essay includes and illustrtion of Earth illuminated by the Sun with stars having "a past or future view of Earth as a transiting exoplanet appear highlighted.