{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"6375b49e47d249f74b8bc20d88d5162ffc3c24a2555b417c60bf63221102dbd4","created":"2026-10-03T07:17:54Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"25398404dc3eddbff33d221030778a1f2973c782423255647e321fb5a5690b62","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"astro.biosignatures.eta-earth","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"The fraction of Sun-like stars with an Earth-size planet at a distance where water could be liquid sets how many targets future telescopes can study. Current estimates differ by about a factor of ten.","posed_since":"","precise":"Measure $\\eta_{\\mathrm{Earth}}$, the number per G and K dwarf of planets with $R = 0.5-1.5\\,R_{\\mathrm{earth}}$ in the conservative habitable zone. Kepler-based estimates span roughly 0.05-0.6 because of extrapolation in period and radius and stellar property uncertainties. The answer is a value with uncertainty below $\\sim 30\\,\\mathrm{percent}$.","problem_ref":null,"references":"","settled_by":"A transit survey of bright Sun-like stars with sensitivity to Earth analogs over multi-year baselines (e.g., ESA PLATO), with radial-velocity mass follow-up.","status_note":"","title":"How common are Earth-size planets in habitable zones of Sun-like stars?","topic_ref":"59b283291ab553a122fd70aabfbd2c1ce03ef623f8bb56636d5ec28be91c14ab"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"acec1fa3e365c28f216f060c6e80c64d72eb3d1ee9eb25bf00f82874e1a2d4b1","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"1ba97630a79363fa14c8e6ff3e239ebcf745a2fa1080a8e680bfd997c4f599b5","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"_VBDl5R8QE0JIk-aaNCMC3c9pwFmCSLuXKVWaYoGATPCeLKRkY63Dl62nRfpDYnFH48xYI2qLz9pLPNy_IrtAw"},"schema":"pubphys.envelope/1"},"record_hash":"acec1fa3e365c28f216f060c6e80c64d72eb3d1ee9eb25bf00f82874e1a2d4b1","leaf_index":485}