Which region around the solar system is a spherical shell far beyond the planets?

• A. Kuiper belt
• B. Oort cloud
• C. Asteroid belt
• D. Zodiacal cloud

Answer: (B)

A spherical shell surrounding the Sun at great distances describes the Oort cloud. It’s thought to extend from thousands to tens of thousands of astronomical units, even up to around 100,000 AU, far beyond the outer planets. Objects there are icy remnants from the solar system’s formation and can be nudged by passing stars into long, elongated orbits that send comets inward. This spherical, distant distribution contrasts with the Kuiper belt, which lies in a flattened disk beyond Neptune at about 30–50 AU, the asteroid belt between Mars and Jupiter, and the zodiacal cloud of dust spread mainly through the inner solar system along the ecliptic plane. Because the region described is a distant, spherical shell, the Oort cloud fits best.