Why stars inflate to and deflate from red giant dimensions

Abstract

view Abstract Citations (55) References (71) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Why Stars Inflate to and Deflate from Red Giant Dimensions Renzini, Alvio ; Greggio, Laura ; Ritossa, Claudio ; Ferrario, Lilia Abstract It is demonstrated that stars become red giants in response to the increasing luminosity being provided by the stellar core, and that the runaway expansion - when it takes place - is triggered by the thermal conductivity in the envelope reaching a maximum and then decreasing. It is shown that the decrease in thermal conductivity at each point in the envelope causes part of the radiative energy flow to be trapped locally, which causes further expansion and further departure from thermal equilibrium. Thermal equilibrium in the stellar envelope is restored by the onset of convection, as the star approaches the Hayashi line. A general criterion for thermal stability is formulated, and it is shown that when it is violated, the envelope undergoes either runaway expansions to, or runaway deflations from, red giant dimensions, depending on the previous evolution. Publication: The Astrophysical Journal Pub Date: November 1992 DOI: 10.1086/171995 Bibcode: 1992ApJ...400..280R Keywords: Late Stars; Red Giant Stars; Stellar Interiors; Thermodynamic Equilibrium; Inflating; Stellar Cores; Stellar Luminosity; Astrophysics; STARS: INTERIORS; STARS: LATE-TYPE full text sources ADS | data products SIMBAD (1)