Reflecting on the Brightness of Stars

What can explain Eduardo's observation that the star Regulus is brighter than the star Rigel, even though Rigel has a greater absolute brightness?

A) Rigel is a hotter star than Regulus.

B) Regulus is a smaller star than Rigel.

C) Regulus is much closer to Earth than Rigel.

D) Rigel is much closer to Earth than Regulus.

Final answer:Regulus appears brighter than Rigel to Eduardo because C) Regulus is much closer to Earth than Rigel.

Explanation:

Eduardo's observation that the star Regulus is brighter than the star Rigel, even though Rigel has a greater absolute brightness, can be explained by the fact that Regulus is much closer to Earth than Rigel. This is because apparent brightness depends on both the absolute brightness of a star and its distance from the observer. Despite its lower absolute brightness, the proximity of Regulus to Earth makes it appear brighter in our sky than Rigel, which is farther away.

Absolute brightness, or luminosity, is an intrinsic property of a star that indicates how much light it emits from its surface, irrespective of how far away it is. For two stars with the same spectral type, the larger one will generally have greater luminosity. However, this does not necessarily mean it will appear brighter from Earth. Apparent brightness is what we actually see, and it is influenced by the star's distance from Earth.

If two stars have identical luminosities but are at different distances from us, the nearer one will appear brighter, as illustrated by the example of Star A and Star B; if Star A is closer, it will appear brighter than Star B, even with the same luminosity.