by Empeda2 » Thu Jan 12, 2006 2:06 pm
Current stellar theory suggests that the type of star that would produce a planetary nebula (if, for simplicity's sake, we assume the star form from almost pure Hydrogen), would probably only created elements up to Carbon, Oxygen and Nitrogen through fusion processes.
What that image is showing is the star 'shedding' it's outer envelope, this would contain mainly hydrogen and helium, leaving the 'core' as a white dwarf, composed mainly of Carbon, Oxygen and Nitrogen. This will slowly cool to become a black dwarf (not a black hole!) and there is no fusion processes to maintain it's temperate.
To get larger elements in this way, you need a larger star, that has enough mass to fuse C, N and O to heavier elements - up to 56Fe (the most stable isotope).
This is a highly simplistic description but shows the basis for current stellar theory. Stars such as our sun for example, would not have formed from pure hydrogen, and would already have some heavy elements in it at formation.
Current stellar theory suggests that the type of star that would produce a planetary nebula (if, for simplicity's sake, we assume the star form from almost pure Hydrogen), would probably only created elements up to Carbon, Oxygen and Nitrogen through fusion processes.
What that image is showing is the star 'shedding' it's outer envelope, this would contain mainly hydrogen and helium, leaving the 'core' as a white dwarf, composed mainly of Carbon, Oxygen and Nitrogen. This will slowly cool to become a black dwarf (not a black hole!) and there is no fusion processes to maintain it's temperate.
To get larger elements in this way, you need a larger star, that has enough mass to fuse C, N and O to heavier elements - up to 56Fe (the most stable isotope).
This is a highly simplistic description but shows the basis for current stellar theory. Stars such as our sun for example, would not have formed from pure hydrogen, and would already have some heavy elements in it at formation.