Introduction
- The following pages are a first attempt at explaining stellar
evolution in a phenomenological, rather than quantitative, way. The aim is to
give you an informed overview of the physics of the various stages, the
things that occur, and importantly, the nucleosynthesis which occurs. The
graphs are from recent calculations (details given below) and are not
schematic (unless explicitly stated). But don't worry about the numbers.
Its the overall behaviour that is important.
- Obviously these pages cannot teach you all the maths and physics you need to understand the evolution! It is assumed that you have enough background in that already. These pages are perhaps best used as an adjunct to a normal course in stellar evolution and nucleosynthesis.
- My own interest is in explaining the complex behaviour of AGB stars to non-experts. But the rest of the tutorial, from the ZAMS to the AGB, is a required background and s suitable for courses which do not go as far as the AGB evolution, or are not interested in the nucleosynthesis.
- Please note: you are free to copy these and use them for educational purposes, just be sure to credit where you got them from. If you want to use them for some commercial purposes, then we should talk
- If you re using these for teaching purposes, I would like to
know your name, the number of students, involved, the level of the course,
etc. I am also seeking comments on how to improve these presentations, so
please feel free to email me
with comments and criticisms. Any suggestions for clarification, in text
of graphs, would be welcome.
- A note on time.... The movies show time-dependence, but its important to realise that this is not linear! In fact, the times were chosen to illustrate features of the evolution. The frames were picked so that the feature we were looking at was clearly seen, independent of the time. This means that sometimes the time between successive frames is dramatically different. In the movies with two frames next to each other, one of the frames usually indicates the time, so in those cases the rate of the movie is obvious. But beware that in other cases the times between frames vary a lot!
- I tried to make the labels large,m without taking up too much space in the graph. Some of the lines are too thick, I now realise. These will be fixed in the next generation of movies.
- Some of the movies show two frames at a time, such as the internal evolution and the corresponding position in the HR diagram. For these movies you have the choice of the two frames appearing either horizontally (graphs next to each other) or vertically (one above the other). Choose whichever fits your screen best.
- Please note: no stars were harmed during the making of these movies....
Overview
- We will follow the evolution of two stars, from the main-sequence through to the thermally-pulsing AGB, which is essentially the end of their lives. We have chosen two masses: M=1 Msun and M=5 Msun; both have essentially a solar composition with X=0.6872, Y=0.2928 and Z=0.02.
- If you want to see the evolution of massive stars, including supernova models, then see the movies by Alexander Heger and collaborators
- The figure below shows the evolution of both stars and
identifies the Early-AGB and the Thermally-Pulsing AGB.
Evolution for M = 1 Msun and Z=0.02
Evolution for M = 5 Msun and Z=0.02
Asymptotic Giant Branch Evolution (for M = 5 Msun and Z=0.02)
Nucleosynthesis on the AGB (for M = 5 Msun and Z=0.02)
- General nucleosynthesis here
- Nucleosynthesis in thermal pulses is here
- Nucleosynthesis by Hot Bottom Burning here