Near-unstable supergiants.
Abstract
The instability of massive supergiant stars is discussed in light of the absence of massive luminous cool supergiants. Consideration is given to the Eddington limit to stellar luminosities and the dissipation of turbulent energy by massive stars, and it is shown that these processes are insufficient to explain in the absence of red supergiants larger than about 25 solar masses. It is suggested that in the course of evolution towards low temperatures, massive supergiants retrace their steps on the Hertzsprung-Russel diagram and move to the region of higher photospheric temperatures. Such stars would become unstable as the ratio of specific heats approaches 4/3, and would begin to pulsate, as is observed in all stars more than approximately 10,000 times brighter than the sun. It is suggested that these instabilities would most likely originate in the convection layers just below the stellar surface, and would lead to the formation of stellar coronas as detected by ANS and the HEAO-2 satellites.
- Publication:
-
ESA Journal
- Pub Date:
- 1980
- Bibcode:
- 1980ESAJ....4..123D
- Keywords:
-
- Hertzsprung-Russell Diagram;
- Stellar Evolution;
- Stellar Luminosity;
- Supergiant Stars;
- Systems Stability;
- Energy Dissipation;
- Solar Flux;
- Stellar Coronas;
- Stellar Gravitation;
- Stellar Radiation;
- Astrophysics;
- Atmospheres:Supergiants;
- Supergiants:Stability