Star A is a main sequence star of spectral type G5 and star B is a red giant of spectral typeK2. Which statement below is correct?
A)Star A appears brighter than star B.
B)Star B appears brighter than star A.
C)Star A is hotter than star B.
D)Star B is hotter than star A.
E)None of the above can be said about these two stars.

Question

Quizplus · Accepted Answer

Star A is of spectral type G5, meaning it is a yellow main sequence star with a surface temperature of approximately 5,500 K. Star B, on the other hand, is a red giant of spectral type K2, meaning it has a much cooler surface temperature of approximately 4,000 K. Therefore, star A is hotter than star B. The brightness of the stars cannot be determined based on spectral type alone. Spectral type is a measure of a star's surface temperature. A main sequence star of spectral type G5 is hotter than a red giant of spectral type K2. Therefore, star A (G5) is hotter than star B (K2). The brightness of a star is also affected by its temperature, but it is also dependent on its size and distance from us, so we cannot determine which star appears brighter without additional information.

Star a Is a Main Sequence Star of Spectral Type