bbbl67 said:For example, red dwarfs can fuse their entire hydrogen allocation, so the whole star is the core.
Well, you tell me what definitions of "core" there are that you know of.nikkkom said:Depends on the definition what "core" is.
So what you're saying is that during the main sequence phase, all large stars (i.e. not red-dwarfs), from the Sun on up to R136a1, will have an approximately 0.3 solar mass core? That the largest stars just burn through their 0.3 SM cores faster?Ken G said:I believe the solar value of around 30% of the mass in the core is fairly ubiquitous for main-sequence stars, where "core" means the region where central fusion is happening when it is happening, or the region inside the shell fusion when it isn't. For stars that eventually achieve core helium burning, most have that occur when the core mass (of pure helium) is about a half a solar mass, so in the core helium fusing phase, it's not the fractional mass but the total mass of the core that tends to be similar. Then shell helium fusion adds even more to that, so what ends up being the core when the envelope is shed and a white dwarf is made can be more like a solar mass (for stars that have had time to make white dwarfs).
bbbl67 said:Well, you tell me what definitions of "core" there are that you know of.
The relationship between stellar mass and core mass is a direct one, with the core mass being a smaller fraction of the total stellar mass for smaller stars and a larger fraction for larger stars. This is due to the fact that smaller stars have lower temperatures and pressures in their cores, making it easier for nuclear fusion to occur and thus requiring a smaller core mass to sustain the star's energy production.
The relationship between stellar mass and core mass has a significant impact on a star's lifespan. Generally, the larger the core mass is in relation to the total stellar mass, the shorter the star's lifespan will be. This is because a larger core mass means a higher rate of nuclear fusion, resulting in a faster depletion of the star's fuel and a shorter overall lifespan.
Core mass plays a crucial role in a star's evolution. As a star ages and burns through its fuel, its core mass increases due to the fusion of lighter elements into heavier ones. This increase in core mass can eventually trigger a change in the star's structure and behavior, leading to events such as the expansion into a red giant or the collapse into a supernova.
Yes, the relationship between stellar mass and core mass can vary among different types of stars. For example, low-mass stars like red dwarfs have a larger core mass in proportion to their total stellar mass compared to high-mass stars like blue giants. This is due to differences in their internal temperature and pressure profiles, as well as the type of nuclear fusion occurring in their cores.
Measuring the core mass of a star is a challenging task, as the core is often hidden beneath the star's outer layers. However, scientists can use various techniques such as asteroseismology, which studies the oscillations of a star's surface to infer its internal structure and core mass. They can also use observations of a star's luminosity and temperature to estimate its core mass through theoretical models and comparisons with other stars of similar mass and evolutionary stage.