One of Everything: The Breakthrough Listen Exotica Catalog
Brian C. Lacki · Bryan Brzycki · Steve Croft · Daniel Czech · David DeBoer
The Astrophysical Journal Supplement Series · 2021
Breakthrough Listen's Exotica Catalog compiles 963 entries across 816 distinct targets spanning every known astrophysical object class, formalizing 'survey breadth' as a third dimension of SETI target selection alongside depth and count.
Brief
Lacki et al. (2021) introduce the Breakthrough Listen Exotica Catalog, a 963-entry, 816-distinct-target list designed to include 'one of everything' in astronomy and correct what the authors argue is a systematic bias in SETI toward high-depth, low-breadth programs. The catalog is divided into four samples: Prototype (an archetype of every known non-transient object class), Superlative (objects at the tails of observed property distributions), Anomaly (unexplained sources including prior published ETI candidates), and Control (unphysical or mundane objects for systematic characterization). The paper frames the catalog's rationale through five motivations ranging from constraining exotic ETI habitats to identifying natural signals that mimic artificial ones. Observations are planned across Breakthrough Listen's full instrument suite, Green Bank Telescope, Parkes, MeerKAT, the Automated Planet Finder, and VERITAS, with accompanying online notes for all 963 entries.
Metadata
- Category
- Search
- Venue
- The Astrophysical Journal Supplement Series
- Type
- Peer-reviewed
- Year
- 2021
- Authors
- Brian C. Lacki, Bryan Brzycki, Steve Croft, Daniel Czech, David DeBoer
- arXiv
- 2006.11304
- Access
- Open access
- Length
- 3.3 M
- Programs
- Breakthrough Listen, Project Phoenix, META, Astropulse, HabCat
- Instruments
- Green Bank Telescope, CSIRO Parkes Telescope, MeerKAT, Automated Planet Finder, VERITAS
- Data sources
- Breakthrough Listen Exotica Catalog (963 entries, 816 distinct targets)
- Tags
- SETI, technosignature, survey-methodology, catalog, anomaly-classification, commensal-astrophysics, astrobiology
Key points
- The catalog contains 963 entries covering 816 distinct targets; the authors describe it as 'the first object list in recent times with the purpose of spanning the breadth of astrophysics.'p.1
- Four structured samples: Prototype (non-transient archetypes), Superlative (extreme-property objects), Anomaly (unexplained sources), and Control (unphysical or mundane sources for systematic characterization).p.1
- The paper formalizes three dimensions of survey design, breadth (variety of object types), count (number of examples per type), and depth (integration time per object), arguing prior SETI surveys have over-indexed on depth and count.p.3
- Five core motivations are stated: constraining exotic ETI habitats, evaluating whether astrophysical phenomena are artificial, identifying natural ETI mimics, enabling commensal astrophysics with Breakthrough Listen instrumentation, and characterizing systematics that could generate false positives.p.5
- The Anomaly sample explicitly includes previously published ETI candidates as a sub-sample, treating them under Motivations I, II, and III simultaneously.p.7
- Control sample targets include 'unphysical' pointings such as the zenith, intended to characterize instrumental behavior and RFI where no astrophysical signal is expected.p.7
- Breakthrough Listen's upcoming MeerKAT commensal program will survey one million stars, the largest count in targeted SETI history, but the authors note its breadth is limited because object types covered 'are not too rare, unconventional, or extreme.'p.5
- EIRP (equivalent isotropic radiated power) is used as the standard metric for constraining transmitter power across all campaign and catalog observations.p.6
Verbatim
“It contains four samples: the Prototype sample, with an archetype of every known major type of non-transient celestial object; the Superlative sample of objects with the most extreme properties; the Anomaly sample of enigmatic targets that are in some way unexplained; and the Control sample with sources not expected to produce positive results.”
p.1“As far as we are aware, this is the first object list in recent times with the purpose of spanning the breadth of astrophysics.”
p.1“hot Jupiters were speculated about in the 1950s (Struve 1952), but they were not discovered until 1995 in part because no one systematically looked for them”
p.2
Most interesting
- Ceres was discovered serendipitously in January 1801 by Giuseppe Piazzi while constructing a star catalog, he was one of 24 astronomers assigned to search for the planet predicted by the Titius-Bode Law, but did not know he had been selected when he found it.
- Pulsars were briefly considered possible ETI signals after their 1968 discovery due to the regularity of their radio pulses, a case study the authors use to motivate including known natural ETI-mimic sources in the catalog.
- The Control sample includes the zenith, a pointing at a celestial non-object, as a deliberate observation target, treating it as a scientific tool for instrument characterization.
- Ultracompact dwarf galaxies were only recognized as a class in 2001 despite being visible in archival images for decades, an example the authors cite of discoveries delayed by failure to look rather than failure of capability.
- The catalog's Superlative sample distinguishes between objects that are extreme because they are genuine statistical outliers (S1), represent unrecognized new subclasses (S2), or are only apparently extreme because fainter examples cannot be detected (S3).
- The authors explicitly flag that parameter space volume is parameterization-dependent, volume looks vastly different when using wavelength versus frequency, and argue Bayesian probability distributions over parameter space are more meaningful than raw volume metrics for evaluating SETI survey value.