Question

question 18
which of the following statements about spectral types of stars is true?
a star with spectral type b is always cooler than a star with spectral type f.
a star with spectral type o star is always bluer than a star with spectral type m.
stars with spectral type m or k are a lot less common than o or b stars.
a star with spectral type f5 is always hotter than a star with spectral type f1.

Explanation:

The spectral sequence of stars in order of decreasing temperature is O, B, A, F, G, K, M. O - type stars are the hottest and bluest, while M - type stars are the coolest and reddest. A star with spectral type O is always bluer than a star with spectral type M. A star with spectral type B is hotter (not cooler) than a star with spectral type F. Stars of spectral types M and K are more common than O and B stars. In the F - type sub - classification, a lower number (e.g., F1) indicates a hotter star than a higher number (e.g., F5).

Answer:

B. A star with spectral type O star is always bluer than a star with spectral type M.