Question

Consider how a star like the Sun changes after the Main Sequence. Put the following events in the correct order.

1. The outer layers of the star drift off into space creating a planetary nebula.

2. Helium fusion in the core of the star ends

3. The hot, dense core of the star is left behind as a white dward that slowly cools and dims over time.

4. The star shrinks slightly, compressing a shell of hydrogen surrounding the non-burning helium core.

5. The shell surrounding the non-burning carbon/oxygen core begins to fuse helium, and the shell outside of that fuses hydrogen.

6. The star's core becomes hot enough and dense enough to begin fusing helium to carbon and oxygen, causing it to collapse inward somewhat.

7. Shell hydrogen fusion is disrupted and the star shrinks slightly

8. Fusion of hydrogen to helium in the core of the star ends.

9. The star shrinks slightly, compressing a shell of helium surrounding the non-burning carbon/oxygen core, and a shell of hydrogen surrounding the region of helium

10. The star's surface becomes cooler and the star's luminosity increases; the star is now a "red giant."

11.Hydrogen shell fusion causes the outer layers of the star to expand outward.

12. The star's surface becomes cooler and the star's luminosity increases; the star is now an "asymptomatic giant."

13. Shell fusion of hydrogen and helium cause the outer layers of the star to expand outward.

14. The shell surrounding the non-burning helium core begins to fuse hydrogen

15. The star's surface becomes somewhat hotter and the star's luminosity decreases slightly; the star is now a "horizontal branch" star

Answer 1

The order of events are :

14. The shell surrounding the non-burning helium core begins to fuse hydrogen

13. Shell fusion of hydrogen and helium cause the outer layers of the star to expand outward.

10. The star's surface becomes cooler and the star's luminosity increases; the star is now a "red giant."

6. The star's core becomes hot enough and dense enough to begin fusing helium to carbon and oxygen, causing it to collapse inward somewhat.

15. The star's surface becomes somewhat hotter and the star's luminosity decreases slightly; the star is now a "horizontal branch" star

5. The shell surrounding the non-burning carbon/oxygen core begins to fuse helium, and the shell outside of that fuses hydrogen.

9. The star shrinks slightly, compressing a shell of helium surrounding the non-burning carbon/oxygen core, and a shell of hydrogen surrounding the region of helium

4. The star shrinks slightly, compressing a shell of hydrogen surrounding the non-burning helium core.

7. Shell hydrogen fusion is disrupted and the star shrinks slightly

8. Fusion of hydrogen to helium in the core of the star ends.

12. The star's surface becomes cooler and the star's luminosity increases; the star is now an "asymptomatic giant."

11.Hydrogen shell fusion causes the outer layers of the star to expand outward.

1. The outer layers of the star drift off into space creating a planetary nebula.

2. Helium fusion in the core of the star ends

3. The hot, dense core of the star is left behind as a white dward that slowly cools and dims over time.