{"paper":{"title":"Models of the Mass-Ejection Histories of pre Planetary Nebulae. II. The Formation of the Butterfly and its Proboscis in M2-9","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"","cross_cats":[],"primary_cat":"astro-ph.SR","authors_text":"Adam Frank, Baowei Liu, Bruce Balick, Romano Corradi","submitted_at":"2017-11-30T20:06:28Z","abstract_excerpt":"M2-9, or the \"Butterfly Nebula\" is one of the most iconic outflow sources from an evolved star. In this paper we present a hydrodynamic model of M2-9 in which the nebula is formed and shaped by a steady, low-density (\"light\"), mildly collimated \"spray\" of gas injected at 200 km s^-1 that interacts with a far denser, intrinsically simple pre-existing AGB wind has slowly formed all of the complex features within M2-9's lobes (including the knot pairs N3/S3 and N4/S4 at their respective leading edges, and the radial gradient of Doppler shifts within 20\" of the nucleus). We emphasize that the knot"},"claims":{"count":0,"items":[],"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"source":{"id":"1712.00056","kind":"arxiv","version":2},"verdict":{"id":null,"model_set":{},"created_at":null,"strongest_claim":"","one_line_summary":"","pipeline_version":null,"weakest_assumption":"","pith_extraction_headline":""},"references":{"count":0,"sample":[],"resolved_work":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}