Which term describes the brightness a star would have at a standard distance from Earth?

• A. Absolute brightness
• B. Apparent magnitude
• C. Light year
• D. Astronomical Unit (AU)

Answer: (A)

The brightness a star would have at a standard distance from Earth is described by absolute magnitude. This measures intrinsic brightness by imagining the star at a fixed distance (10 parsecs, about 32.6 light-years) so we can compare how bright stars truly are, without distance affecting the result. Apparent magnitude, in contrast, is how bright a star looks from Earth right now, which changes with how far away the star is and what interstellar material might dim the light. A light year is a unit of distance, and an astronomical unit is the average distance between the Earth and the Sun—neither describes brightness. So the best term for this concept is absolute magnitude.