I am pleased to report that UCLA graduate student Paul Pinchuk and I have completed a manuscript that describes the analysis of our Spring 2017 Green Bank Telescope data. Our observations focused on ten planetary systems in the Kepler field, the TRAPPIST-1 system, and LHS 1140. The manuscript is now being reviewed by our co-authors, i.e., the students who took the Spring 2017 SETI course, SETI alumnus Adam Greenberg (now at Raytheon), and GBT collaborator Ryan Lynch. In addition to our analysis in the manuscript, we also address a problem that is common in radio technosignature detection pipelines and that affected our results to date as well as results published recently by the Breakthrough Listen project. The problem arises when certain algorithms are invoked to eliminate suspected radio frequency interference or to avoid duplicate detections of the same signal. These algorithms have a negative side effect: entire windows of frequency space are discarded around candidate detections. In recent works, these windows have been as large as 400 to 1000 times the width of individual channels, large enough to result in the loss of many legitimate signals. The problem affects the number of reported detections and the estimates of search effectiveness, but more importantly, it calls into question published claims about the prevalence of extraterrestrial radio emitters in the Galaxy. Because detectable technosignatures may be present at frequencies that are eliminated by the detection algorithms, converting the absence of a detection into limits on the number of radio emitters is problematic. This difficulty explains why we have prudently refrained from publishing such estimates.
Paul designed and implemented an elegant solution to eliminate the negative side effects of these data-processing algorithms. As a result, the number of candidate detections identified by our pipeline has considerably increased. The improvement is so notable that we decided to also reprocess our entire 2016 data set and to present the updated analysis in our manuscript. Although the main conclusions of our previous analysis did not change, comparing the two methods proved very instructive so we are glad that we took on the additional work. Testing new detection algorithms on the 2016 data was only possible because we made a conscious decision to preserve the raw data that we obtained. This choice is a competitive advantage of our approach and we hope to preserve it even as we scale up our search efforts. Paul and I will present our most recent results in two talks at the meeting of the American Astronomical Society in Seattle, WA, on January 10, 2019.
In my last newsletter, I reported briefly on the NASA Technosignatures Workshop that took place in Houston, TX, on September 26-28, 2018. The quality of the talks at the workshop was highly variable, with some excellent overviews of the state of the art in various areas as well as some remarkable duds. What struck me in particular is that a number of the non-radio technosignature search proposals will almost certainly yield ambiguous results and decade-long debates, similar to what many experts expect for biosignature results in the foreseeable future (with the possible exception of finding evidence of metabolism, fossils, or DNA-like structures in a Solar System environment). For this reason, attending the NASA workshop and co-authoring the workshop report for NASA renewed my preference for the search at radio wavelengths: if we detect repeatable, narrowband or artificially pulsed emission from an extraterrestrial emitter, it is reasonable to expect that such evidence will be regarded as unambiguous and compelling by most scientists. It took six decades to fully refute Percival Lowell's claims of canals on Mars but less than a day to witness wide acceptance of the detection of gravitational waves by LIGO. This analogy is not perfect but still useful when comparing searches for markings on exoplanet surfaces or gases in exoplanet atmospheres and searches for radio emitters.
We will have an opportunity to argue the merits of various search techniques in white papers submitted to the Astro2020 decadal survey organized by the U.S. National Academy of Sciences. This survey is an important instrument that guides funding priorities in astronomy for many years. I am the lead author of a paper titled "The radio search for technosignatures in the decade 2020-2030" and co-author of various other papers. Submissions are due on February 19, 2019.
You have probably heard about the successful landing of NASA's InSight mission on Mars today. Three of my UCLA colleagues are involved with the mission and I am looking forward to hearing about the findings.
Warm regards,
Jean-Luc Margot
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