Stellar evolution: initial mass changes the route
| English | 中文 | Pinyin |
|---|---|---|
| main sequence/meɪn ˈsiːkwəns/ | 主序 | zhǔ xù |
| white dwarf/waɪt dwɔːf/ | 白矮星 | bái ǎi xīng |
What would explain this observation?
- The Sun and a very massive star do not have the same final remnant. A life-cycle diagram must branch according to initial mass.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A star forms from a collapsing cloud of gas and dust. A stable main-sequence 主序 star releases energy by nuclear fusion, while gravity and outward pressure maintain its structure. A lower-mass star can pass through a red-giant stage to a white dwarf 白矮星; a sufficiently massive star can undergo a supernova and leave a neutron star or black hole.
- main sequence: A stable stellar phase sustained by core hydrogen fusion; white dwarf: A compact remnant on the lower-mass stellar route.
Which final route is appropriate for the Sun in the school model?
Read a life-cycle diagram as a model of stages and conditions, not a timed film of one star. The Sun is expected to follow the lower-mass route. Fusion combines light nuclei; it differs from fission of a heavy nucleus.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Read a life-cycle diagram as a model of stages and conditions, not a timed film of one star. The Sun is expected to follow the lower-mass route. Fusion combines light nuclei; it differs from fission of a heavy nucleus.
- Compare attributed stellar observations with predicted properties of each stage. Keep star, planet, galaxy and universe distinct. An orbiting body can have constant speed while its velocity changes direction.
Which two habits make the investigation or model in this case more defensible?
Compare attributed stellar observations with predicted properties of each stage. Keep star, planet, galaxy and universe distinct. An orbiting body can have constant speed while its velocity changes direction.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: in an illustrative sample, 8 of 40 observed stars are in a selected stage. Sample percentage = 8/40 × 100 = 20%. This descriptive fraction does not directly measure stage duration because observation and selection effects matter.
6 of 30 stars in an illustrative sample are in a chosen stage. Calculate the percentage. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
6 of 30 stars in an illustrative sample are in a chosen stage. Calculate the percentage.
The result is 20 %. Known: in an illustrative sample, 8 of 40 observed stars are in a selected stage. Sample percentage = 8/40 × 100 = 20%. This descriptive fraction does not directly measure stage duration because observation and selection effects matter.
Check the conclusion and its limits
- The Sun is not expected to become a supernova. A diagram does not establish that every massive star makes the same remnant, nor that all stages last the same time.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
The Sun is expected to end in a supernova. This claim is false: The Sun is not expected to become a supernova. A diagram does not establish that every massive star makes the same remnant, nor that all stages last the same time.
Stellar evolution: initial mass changes the route: Read a life-cycle diagram as a model of stages and conditions, not a timed film of one star. The Sun is expected to follow the lower-mass route. Fusion combines light nuclei; it differs from fission of a heavy nucleus.
The Sun is expected to end in a supernova.
The Sun is not expected to become a supernova. A diagram does not establish that every massive star makes the same remnant, nor that all stages last the same time.
A stable stellar phase sustained by core hydrogen fusion: write the technical term.
main sequence means A stable stellar phase sustained by core hydrogen fusion.