Which term describes a model with the Sun at the center of the solar system?

• A. Absolute Magnitude
• B. Color-Magnitude Diagram
• C. Phases of the Moon
• D. Heliocentric Theory

Answer: (D)

This question tests understanding of a Sun-centered model of the solar system—the heliocentric theory. It states that the Sun sits at the center and planets, including Earth, orbit around it. This idea contrasts with earlier geocentric thinking that placed Earth at the center. The term heliocentric theory names this arrangement, and it aligns with how gravity shapes planetary motions, giving us the roughly circular orbits and the changing positions of planets over time. The other terms describe different astronomical ideas: absolute magnitude is about a star’s intrinsic brightness at a standard distance; a color-magnitude diagram compares stars’ brightness to their color; phases of the Moon describe the Moon’s changing appearance from Earth.