Stellar Evolution
5 marks · NormalThe table below shows data for three stars: Sirius, Betelgeuse, and Rigel. All three are located in the Milky Way.
| Star | Class | Surface temperature (K) |
|---|---|---|
| Sirius | A | 9500 |
| Betelgeuse | M | 3200 |
| Rigel | B | 12100 |
For each star, state the likely colour you would observe.
Describe the likely stage in the stellar life cycle for Betelgeuse and Rigel, based on their classification.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Sirius: white; Betelgeuse: red; Rigel: blue or blue-white.
(b) Betelgeuse is a red supergiant near the end of its life; Rigel is a hot, massive star, possibly a supergiant, likely to end as a supernova.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States Sirius appears white.
B2 (a) · 1 mark · States Betelgeuse appears red.
B3 (a) · 1 mark · States Rigel appears blue or blue-white.
B4 (b) · 1 mark · Describes Betelgeuse as a red supergiant near the end of its life cycle.
B5 (b) · 1 mark · Describes Rigel as a hot massive star, possible supergiant, that will end in supernova and possibly become a neutron star or black hole.
Worked solution
a) Sirius (A-class, 9500 K) appears white. Betelgeuse (M, 3200 K) is red. Rigel (B, 12100 K) is blue or blue-white.
b) Betelgeuse, as an M-class star with low temperature, is a red supergiant—late in its life. Rigel, a hot B-class star, is a massive star likely heading towards a supernova ending.