The Life of a Star
4 marks · NormalThe table below shows the absolute magnitudes and surface temperatures of three stars:
| Star | Absolute Magnitude | Surface Temperature (K) |
|---|---|---|
| Alpha | 3.5 | 6,000 |
| Beta | −5.0 | 18,000 |
| Gamma | 12.0 | 3,500 |
Which star is the brightest? Explain your answer.
Which of the stars is likely to be a white dwarf? Give a reason for your choice.
State what the star Beta's temperature suggests about its stage in its lifecycle.
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) Beta
(b) Gamma is likely to be a white dwarf. White dwarfs are faint (high magnitude) and have lower temperatures.
(c) Beta’s high temperature (18,000 K) suggests it is a main sequence or possibly recently formed star, so it is near the start or middle of its lifecycle.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies Beta as the brightest star and gives a reason (most negative/lowest magnitude).
B2 (b) · 1 mark · Correctly links Gamma to a white dwarf based on its high absolute magnitude and low temperature.
B3 (c) · 2 marks · Identifies Beta as a hot star; relates to early or main sequence phase. 1 mark per valid point.
Worked solution
a) Beta is the brightest. Absolute magnitude measures brightness: lower (more negative) values are brighter.
b) Gamma is likely to be a white dwarf because it is faint (large positive magnitude) and relatively cool compared to the main sequence.
c) Beta has a very high surface temperature (18,000 K), suggesting it is a main sequence or young star; such high temperatures indicate an early or stable stage.