SETI in 2021
Macy J. Huston · Jason T. Wright
Acta Astronautica · 2022
An annual bibliometric review of 98 SETI papers from 2021, documenting BLC1's resolution as terrestrial RFI, new infrared and radio search limits, and a tripling of social/ethical scholarship driven partly by a dedicated indigenous studies journal issue.
Brief
Huston & Wright survey 98 papers and books published in 2021, sorted into six categories using the ADS SETI bibliography as a starting point. The year's most-publicized event was the Breakthrough Listen signal BLC1, detected toward Proxima Centauri with the Parkes Murriyang telescope and subsequently identified as human-made radio-frequency interference. Paper output grew 31% over 2020's 75 entries, with the social aspects category expanding most sharply, from 10 to 28 papers, largely due to a nine-article American Indian Culture and Research Journal special issue on settler science and contact ethics. Instrumental highlights include Breakthrough Listen's MeerKAT program targeting one million Gaia DR2 stars over approximately 13 months, and Kopparapu et al.'s finding that a LUVOIR-class telescope would need several hundreds of hours to detect Earth-level atmospheric NO2 on a nearby exoplanet.
Metadata
- Category
- Search
- Venue
- Acta Astronautica
- Type
- Peer-reviewed
- Year
- 2022
- Authors
- Macy J. Huston, Jason T. Wright
- arXiv
- 2203.11172
- Access
- Open access
- Length
- 367.8 K
- Programs
- Breakthrough Listen, SETI@Home, VASCO, PanoSETI, SERENDIP, Project Ozma II, META, BETA, COGITO in Space, TechnoClimes
- Instruments
- Parkes Murriyang radio telescope, MeerKAT, FAST, TESS, VLT Interferometer, TAIGA-HiSCORE, Irish LOFAR, Sardinia Radio Telescope, Square Kilometre Array, LUVOIR
- Data sources
- ADS SETI bibliography, Gaia DR2, LoTSS-DR1, Palomar Sky Survey
- Tags
- SETI, annual-review, technosignature, radio-SETI, infrared-SETI, Fermi-paradox, Drake-equation, METI, astrobiology, anomaly-detection
Key points
- Total SETI paper count grew from 75 in 2020 to 98 in 2021, with the social aspects category the fastest-growing (10 to 28 papers), partly driven by a nine-article indigenous studies special journal issue.p.2
- BLC1, detected from the direction of Proxima Centauri via Parkes Murriyang, was determined by Sheikh et al. (2021a) to be produced by human-made electronics; follow-up observations found no repeats near the same wavelength.p.2
- Chen & Garrett used the LoTSS-DR1 catalog to examine the infrared-radio correlation of approximately 16,000 galaxies, identifying two Kardashev Type III civilization candidates and flagging the full LoTSS survey as a basis for placing universe-wide upper limits.p.3
- Breakthrough Listen's Czech et al. target selection strategy for MeerKAT aims to observe one million Gaia DR2 stars of well-understood types via commensal observations over approximately 13 months.p.5
- Kaltenegger & Faherty identified 75 nearby stars (within roughly 100 pc) already reached by Earth's artificial radio leakage that could observe Earth transiting the Sun, candidates for targeted SETI transmissions.p.5
- Socas-Navarro et al. introduced the 'ichnoscale' (ι), normalizing technosignature detectability to present-day Earth = 1, as a quantitative comparison framework across mission concepts.p.4
- Kopparapu et al. modeled NO2 as an industrial atmospheric technosignature and found a LUVOIR-class telescope would require several hundreds of hours to detect Earth-level concentrations on a nearby exoplanet.p.6
- Snyder-Beattie et al. analyzed timings of key evolutionary transitions on Earth and concluded expected transition times likely exceed Earth's lifespan, implying extraterrestrial intelligent life may be extremely rare.p.7
Verbatim
“Sheikh et al. (2021a), presented the analysis of the technosignature candidate, which determined that the signal was not extraterrestrial, and instead produced by human-made electronics.”
p.2“This year saw a significant increase in SETI papers from 2020's 75 papers Wright (2021a) to 98.”
p.2“Chen & Garrett (2021) searched for Kardashev Type III civilizations which generate waste heat from Dyson sphere-like structures. They used the LoTSS-DR1 value-added catalog to study the infared-radio correlation of ∼ 16,000 galaxies, finding two galaxies to be Type III civilization candidates for further study and noting the value of extending this analysis to the full LoTSS survey to place upper limits on Type III civilizations in the universe.”
p.3“Czech et al. (2021) presented Breakthrough Listen's target selection strategy for commensal SETI observations on the MeerKAT telescope, which aims to observe a million stars of well-understood types from the Gaia DR2 database over ∼ 13 months.”
p.5“Snyder-Beattie et al. (2021) explored the timings of key evolutionary transitions on Earth and concluded that the expected transition times likely exceed the lifetime of Earth, suggesting that extraterrestrial intelligent life may be extremely rare.”
p.7“Hanson et al. (2021) invoked hard steps in a simple model of "grabby" (or expansive) ETIs, which expand through their galaxy at a constant speed, arising from more common "quiet" civilizations, concluding that non-detection indicates that these quiet civilizations are rare to begin with or that the transition to grabby is exceedingly rare.”
p.7
Most interesting
- A 1950 Palomar Sky Survey plate contained nine point sources appearing in no surrounding exposures and no modern deep surveys; Villarroel et al. considered radioactive bomb particles the most mundane explanation but did not close the case.
- Two SETI-focused PhDs were awarded in 2021: Dr. Sofia Sheikh (Penn State, advised by Jason Wright) and Dr. Paul Pinchuk (UCLA, advised by Jean-Luc Margot).
- The SETI field lost three prominent figures in 2021: Bob Gray (Wow! Signal research), Sasha Zaitsev (coined the term 'METI'), and Lev Gindilis, who attended the foundational 1964 Byurakan conference on extraterrestrial civilizations.
- Golden (2021) used Monte Carlo analysis to estimate the Drake equation's non-longevity factor product at 0.85 ± 1.28 yr⁻¹, in close agreement with Drake's original estimate and the Project Cyclops report.
- Hippke (2021b) proposed that Fock state photons or squeezed light would constitute unambiguously artificial interstellar signals detectable with current technology, opening a quantum channel for SETI searches.
- The nine-article indigenous studies special issue originated from a question Breakthrough Listen posed at a 2018 workshop: 'what would you most want SETI scientists to know about potentially making contact?'