Lesson 180 of 1524
Stars from Adolescence to Old Age
When stars first begin to fuse hydrogen to helium, they lie on the zero-age main sequence.
Practice this chapterWhen stars first begin to fuse hydrogen to helium, they lie on the zero-age main sequence. The core of a red giant is contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core.
The amount of time a star spends in the main-sequence stage depends on its mass. More massive stars complete each stage of evolution more quickly than lower-mass stars.
zero-age main sequence — a line denoting the main sequence on the H-R diagram for a system of stars that have completed their contraction from interstellar matter and are now deriving all their energy…. core of a red giant — contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core. planetary nebula — a shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life (the nebulae glow because of the ultra-violet energy of the…. triple-alpha process — a nuclear reaction by which three helium nuclei are built up (fused) into one carbon nucleus.
Worked example
What does “zero-age main sequence” mean in Stars from Adolescence to Old Age?
- 1Use the wording this chapter gives for zero-age main sequence.
- 2The book says: a line denoting the main sequence on the H-R diagram for a system of stars that have completed their contraction from interstellar matter and are now deriving all their energy….
- 3Do not use the meaning of core of a red giant. That term means contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core.
Result: a line denoting the main sequence on the H-R diagram for a system of stars that have completed their contraction from interstellar matter and are now deriving all their energy…
Why. That is the meaning this chapter gives for zero-age main sequence.
Do not swap zero-age main sequence and core of a red giant. zero-age main sequence means a line denoting the main sequence on the H-R diagram for a system of stars that have completed their contraction from interstellar matter and are now deriving all their energy…. core of a red giant means contracting, but the outer layers are expanding as a result of hydrogen fusion in a shell outside the core.
Practice margin
This chapter
A fresh set from this chapter only. Choose 10 or 20. Multiple choice and fill-in, with no repeat inside the set.