Which rule predicted a planet at about 2.8 AU from the Sun, prompting asteroid searches?

• A. Kepler's Third Law
• B. Gauss's Law
• C. Titus-Bode Law
• D. Hubble's Law

Answer: (C)

This question hinges on a historical rule for how planetary orbits were spaced. The Titus-Bode Law proposed a simple sequence of distances in astronomical units that seemed to fit the planets and even predicted a missing body at about 2.8 AU from the Sun. That specific spacing pointed scientists to search in the region between Mars and the asteroid belt, where Ceres was discovered in 1801, sparking the asteroid hunt and the recognition of a belt of small worlds there. So the rule named after this idea directly led to asteroid searches due to its predicted location.

Kepler's Third Law ties orbital period to distance but doesn't forecast a new planet at a particular distance. Gauss's Law is a principle from electromagnetism, not planetary motion. Hubble's Law describes the expansion of the universe, not the layout of planets.