Question

1. which of the following must be true for a stellar object to be called a dwarf planet?

i. diameter greater than 838 km
ii. orbits the kuiper belt
iii. has not cleared the neighborhood of other objects
i only
i and ii
i and iii
ii and iii

Explanation:

• I: A dwarf planet must have sufficient mass for its self - gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape. Generally, a diameter greater than about 800 - 900 km is a rough indicator for this hydrostatic equilibrium condition.
• II: Not all dwarf planets orbit the Kuiper belt. For example, Ceres is in the asteroid belt.
• III: One of the key criteria for a dwarf planet (as per the International Astronomical Union definition) is that it has not cleared the neighborhood around its orbit.

Answer:

C. I and III