An astronomer gives a talk about the far future of the Sun. The talk explains that the Sun is not massive enough to end as a neutron star or a black hole. I...
Question 1 Report
An astronomer gives a talk about the far future of the Sun. The talk explains that the Sun is not massive enough to end as a neutron star or a black hole. Its core will contract after the red giant stage, while its outer layers form a shell. The audience uses the information to complete a written timeline without needing a diagram.
(a) What is the final stellar remnant of the Sun? [1]
(b) Which stage happens immediately before this remnant forms? [1]
(c) Describe why the Sun will leave the main sequence stage. [2]
Fig. 1 shows two possible paths on a classroom life-cycle chart. The teacher asks students to use the mass of the original star to select a path. Star M has about the same mass as the Sun. Star H has a mass more than 10 times the Sun's mass. Both stars begin as a protostar and spend most of their lives fusing hydrogen.
(a) Which star, M or H, will undergo a supernova? [1]
(b) What is the final remnant most likely to be for star M? [1]
(c) Describe why star H has a shorter main sequence lifetime than M. [2]
(d) Calculate the minimum mass of H if the Sun has a mass of 1 solar mass. [1]
Answer Details
Future of the Sun
- (a) The Sun's final stellar remnant is a white dwarf. [1]
- (b) Immediately before this, it is a red giant; a planetary nebula may form as its outer layers are lost. [1]
- (c) The Sun leaves the main sequence when hydrogen in its core is used up. The fusion rate changes, causing the core to contract and the outer layers to expand. [2]
Comparing stars M and H
- (a) H will undergo a supernova because it began with more than ten times the Sun's mass. [1]
- (b) Star M, with about the Sun's mass, will most likely end as a white dwarf. [1]
- (c) H has a higher fusion rate, so it uses its hydrogen fuel more quickly. Therefore its main-sequence lifetime is shorter. [2]
- (d) H has a mass more than 10 solar masses. [1]
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