Classifying Stars
4 marks · NormalThe following table shows three observed stars and their properties:
| Star | Apparent colour | Surface temperature (K) |
|---|---|---|
| A | red | 2 500 |
| B | blue | 34 000 |
| C | yellow | 5 900 |
Which star is the hottest? Explain your answer.
What is the star class of Star C? Use the class table from the syllabus.
Describe the expected relationship between the colour of a star and its surface temperature.
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) Star B is the hottest because it has the highest surface temperature (34,000 K). · must show identifies B, links temperature to answer
(b) G class · must show G class correct for 5,900 K
(c) As the surface temperature of a star increases, its colour changes from red (coolest), through orange, yellow, white, to blue (hottest). The hottest stars are blue, the coolest are red. · must show describes progression/red–blue, temperature-colour link
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies Star B as the hottest and gives reason (highest temperature).
B2 (b) · 1 mark · G class for 5 900 K is correct.
B3 (c) · 2 marks · Explains that hotter stars are blue, cooler stars are red, notes temperature-colour link.
Worked solution
a) Star B is the hottest as its surface temperature is 34 000 K, much higher than the others.
b) Star C, with 5 900 K, is in the G class according to the star classification in the syllabus.
c) The higher the surface temperature of a star, the bluer the colour, while cooler stars are redder. There is a sequence from red (coolest) to blue (hottest).