The asteroid 243 Ida has its own small moon, Dactyl. (See the photo on p. 394.) Another such system, asteroid 624 Hektor, has a mass of 7.9 × 1018 kg, with its moon orbiting at a radius of 623.5 km and a period of 2.965 days.

(a) Given that the orbital radius of Dactyl is 108 km, and its period is 1.54 days, is the mass of 243 Ida greater than, less than, or equal to the mass of 624 Hektor?

(b) Calculate the mass of 243 Ida.

From Page 394