Classifying Stars
4 marks · NormalA group of students observe three stars through a telescope. The results are recorded in the table below.
| Star | Colour | Estimated surface temperature |
|---|---|---|
| Star A | red | 2500 K |
| Star B | yellow | 5800 K |
| Star C | blue | 33000 K |
State the relationship between the colour of a star and its surface temperature.
Which of these stars is likely to belong to the class O? Explain your answer.
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.
Show answer
(a) The hotter the star, the bluer its colour; cooler stars are red. As temperature increases, star colour changes from red to yellow to blue. · must show States hotter stars are bluer, States cooler stars are redder
(b) Star C; it is blue and has a surface temperature of 33000 K, which matches class O. · must show Identifies Star C, Relates high temperature and blue colour to class O
Common mistakes: Reversing the colour-temperature relationship
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States that hotter stars are bluer/cooler stars are redder.
B2 (a) · 1 mark · States the colour changes from red to blue as temperature increases.
B3 (b) · 1 mark · Identifies Star C as class O candidate.
B4 (b) · 1 mark · Explains that blue stars with the highest temperature are class O.
Worked solution
(a) The colour of a star indicates its surface temperature: cooler stars are red, hotter stars are blue. As the temperature increases, the colour changes from red to yellow to blue.
(b) Star C is likely to belong to class O because it is blue and has a very high surface temperature (33000 K), matching the class O description.