ASTR 101 Study Guide - Quiz Guide: Escape Velocity, Impact Crater, Thrust Fault
Document Summary
Mercury is the smallest (a radius of only 2440 km or 1590 miles) and innermost planet in the solar system. Its orbital period around the sun is 88 days and is the shortest of all the planets in the solar system. It is named after the roman deity mercury, the messenger to the gods. Since it is the closest planet to the sun its greatest elongation is only 28 degrees (i. e. its only visible right after sunset or right before sunrise). Since it is located near the sun at sunrise or sunset, the ancients thought that mercury was two different planets, lucifer and hermes. From its radius (i. e. volume) and mass we calculate it has a mean density of 5. 4 g/cm3 which implies a dense iron (fe) core. All planets form as molten balls, then cool and solidify. The cooling rate is proportional to the amount of material (the planet"s mass) and its surface area (its radius).
