Question

which star is more massive than our sun, but has a lower surface temperature?
40 eridani b
sirius
aldebaran
barnards star

Explanation:

Aldebaran is a red giant star. Red giants are more massive than the Sun (in their earlier stages of stellar evolution, they had more mass than the Sun, and even though some mass loss occurs, they are still more massive than the Sun in the red - giant stage compared to the Sun's current mass). Red giants have lower surface temperatures compared to the Sun. 40 Eridani B is a white dwarf (less massive than the Sun in its current state). Sirius is a main - sequence star (more massive than the Sun but has a higher surface temperature). Barnard's Star is a red dwarf (less massive than the Sun).

Answer:

Aldebaran