From Orbital Mechanics, Third Edition

12.1 Introduction

The solar system consists of a single star (the sun) and nine principal planets that move around the sun in orbital paths that are nearly circular except for that of Pluto, which is highly eccentric. Early man considered the Earth to be the center of the universe and the five planets, Venus, Mercury, Mars, Jupiter, and Saturn, to be divine. The most ancient observations of the planets date back 2000 years B.C. and appear to come from the Babylonian and Minoan civilizations. The term planet means "wanderer" in Greek and refers to the celestial objects that move relative to the stars.

The Egyptians, Greeks, and Chinese once thought of Venus, for example, as two stars because it was visible first in the morning and then in the evening sky. The Babylonians called Venus "Istar," the personification of woman and the mother of the gods. In Egypt, the evening star was known as Quaiti and the morning star Tioumoutiri; to the Chinese, Venus was known as Tai-pe, or the Beautiful White One. The Greeks called the morning star Phosphorus and the evening star Hesperos but, by 500 B.C., the Greek philosopher Pythagoras had come to realize that the two were identical. As time passed, the Romans changed the name of the planet to honor their own goddess of love, Venus.

It was not until the Golden Age of Greece that astronomy as a science was placed on a firm foundation and the Earth and the planets were regarded...

Copyright American Institute of Aeronautics and Astronautics, Inc. 2002 under license agreement with Books24x7

Products & Services
Solar Water Heaters
Solar water heaters concentrate the sun’s thermal energy to heat water for industrial, commercial, and residential use. There are two main types of products: active and passive.
Spectroradiometers are used to measure the spectral power distributions of light sources, monitors, and other illuminants.
Thin Film Monitors
Thin film monitors are used to analyze and/or control thin film deposition rate, composition and properties.
Gear Manufacturing Services
Gear manufacturing services design and fabricate gears to customer specifications.

Topics of Interest

13.1 Introduction Although the natural meteoroid environment has been considered in the designs of past and existing spacecraft, future satellite designs will have to take account of space debris in...

1.1 THE SOLAR SYSTEM 1.1.1 The discovery and description of the planets To appreciate how impressive the night sky must have been to early man it is necessary today to go to a place remote from the...

Overview Much of the history of mathematical and physical thought was inspired by curiosity about the motion of the planets the very same laws that govern the motion of spacecraft. The first...

RETURN TO THE MORNING STAR The first Venus mission in 15 years--and the only one planned this decade--is off on a five-month journey to our nearest planet following a successful launch last week. The...

Image available to supplement research story. . Courtesy Space Telescope Science Institute. Previous stories pertaining to Professor Gould's research: "Study: Search For Life Could Include...