{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"89470040028cbe4967adac400d109627a0076959a267b664412bcc8be1e12c0d","created":"2026-10-03T07:17:55Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"681ad232e232d2b3b58b02117b9cd1798662b719166038465c7aca6536a9283b","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"astro.radius-valley.origin","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Close-in small planets come in two sizes with a gap between them. Starlight boiling away thin hydrogen envelopes, heat from the planet's own core doing the same, or differences in how planets formed could each explain it.","posed_since":"2017","precise":"For planets with $P < 100\\,\\mathrm{d}$ the occurrence rate drops by a factor $\\ge 2$ at $R_p \\sim 1.5-2.0\\,R_{\\mathrm{earth}}$, with the gap center decreasing with period roughly as R ~ P^-0.1. Discriminate between XUV photoevaporation (completed in $\\sim 10^8\\,\\mathrm{yr}$), core-powered mass loss ($\\sim 10^9\\,\\mathrm{yr}$), gas-poor late formation, and a water-world population, using the gap dependence on period, stellar mass, age and metallicity.","problem_ref":null,"references":"","settled_by":"Gap location and depth versus stellar mass, instellation and age in a large sample with precise radii and masses, compared with the distinct scalings predicted by each mechanism.","status_note":"","title":"What produces the gap between super-Earths and sub-Neptunes?","topic_ref":"29eecacca9d688759063e837d47b7481ed1a91ff74dcb512159e65510cf6039a"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"fb7f3de0a8fab5711f05e03646a12394509c61354388184d4f33810f4e2b2f0d","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"a337818e7cacc9d92afff7f3e8e7da3aebeb89a1c552a0d9bceefd5590e171da","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"iBlgBItrEm1RUGefS_X5Rd0lST7GDIwgFoIlgx3B0ms6EYHCBIySxKrNkg1nr-Lex7MB05lg-SYJ8sHVTzY5AA"},"schema":"pubphys.envelope/1"},"record_hash":"fb7f3de0a8fab5711f05e03646a12394509c61354388184d4f33810f4e2b2f0d","leaf_index":596}