{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.topic/1","content_sha256":"8f6d3abdddb98a7de93c8f3acd81c9693676300054246a2413bee74201bc00f9","created":"2026-10-03T07:17:50Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":[],"salt":"7fa551a62c1222b362cf3956ad149b5d23f712b99576641bee29bd74ed7bddb1","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"topic"},"content":{"external_id":"astro.smbh-binaries","field":"astro","n":"1","review_cite":"G. Agazie et al. (NANOGrav Collaboration), The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background, Astrophysical Journal Letters, 2023","review_link":"https://arxiv.org/abs/2306.16213","review_verified":"true","summary":"When galaxies merge, their central black holes should pair up and eventually collide, emitting gravitational waves with periods of years. Pulsar timing arrays (networks of precisely clocked spinning neutron stars) now detect a background of such waves, but its source and how the black hole pairs get close enough to merge are uncertain.","title":"Supermassive black hole binaries and the nanohertz background","topic_ref":null,"why":"The background is a direct probe of how galaxies and their black holes grow by mergers."},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"f9d7d39a2b73b71329d173a2c750a3256b1c03b685945ce091c4d937dee9943c","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"4522e4a8be5b0311989075e1e61cbf3a6da1e1f9f5bb67df4842690dd2b952b9","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"gH7QT8xwUYZIs9jrWUqtGas0yx_joUpiYU5-Y7CiYAlLM0MRabzCEI8tUFuo0Jr151QmoZK65HPIHPpL_A99Cg"},"schema":"pubphys.envelope/1"},"record_hash":"f9d7d39a2b73b71329d173a2c750a3256b1c03b685945ce091c4d937dee9943c","leaf_index":51}