Classifying Stars
2 marks · EasyExplain why two stars of different colours must have different surface temperatures.
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A star's colour depends on its surface temperature; blue stars are hottest, red stars are coolest. Different colours mean different temperatures.
Also accept: Because colour shows temperature - blue is hotter than red, so colours mean different temperatures.
Common mistakes: Assuming size affects colour; Assuming colour is random
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Marking points
B1 · 1 mark · States that a star's colour is determined by its surface temperature.
B2 · 1 mark · Explains that different colours mean different surface temperatures.
Worked solution
A star's colour is determined by its surface temperature. For example, blue stars are the hottest while red stars are the coolest, so different colours indicate different temperatures.