Fig. 1 shows a diagram prepared for visitors at a planetarium. It compares two stars that both start as nebulae. Path X is for a star with a mass like the S...
Question 1 Report
Fig. 1 shows a diagram prepared for visitors at a planetarium. It compares two stars that both start as nebulae. Path X is for a star with a mass like the Sun. Path Y is for a star with a much greater mass. The boxes show stages after each star has spent a long time as a main-sequence star. A main-sequence star stays stable because an outward force caused by radiation balances the inward force of gravity. The presenter asks visitors to use the diagram rather than assume that every star has the same final stage.
(a) Which path is followed by a star with a mass similar to the Sun? [2]
(b) What happens to the balance of forces while a main-sequence star is stable? [2]
(c) Which later stage occurs after a red giant in path X? [2]
(d) When a massive star has exploded, what compact object may be left if its core is very massive? [2]
Answer Details
(a) A Sun-like star follows path X, the lower-mass route. [2]
(b) In a stable main-sequence star, gravity acts inward and radiation pressure, or the outward force from hot gas, acts outward with equal size. The resultant force is zero. [2]
(c) After the red giant stage, a Sun-like star forms a planetary nebula, then a white dwarf. This sequence gains both marks. [2]
(d) If the remaining core is very massive after a massive star explodes, it can form a black hole. [2]
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