4.9 PLANETARY DATA
An astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its gravity is termed a planet. There are more planets in our galaxy than stars.
Our solar system consists of our star, the Sun, and everything bound to it by gravity - the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; dwarf planets such as Pluto; dozens of moons; and millions of asteroids, comets, and meteoroids. Table 4.1 summarizes the physical parameters of the planets in the solar system.
| Planet | Distance from Sun (Gm) | Orbital Period (yr) | Average Surface Temperature (°C) | Mass (1024 kg) | Density (kg/m³) | g (N/kg) |
|---|---|---|---|---|---|---|
| Mercury | 57.9 | 0.330 | 167 | 0.241 | 5429 | 3.7 |
| Venus | 108.2 | 4.87 | 464 | 0.615 | 5243 | 8.9 |
| Earth | 149.6 | 5.97 | 15 | 1 | 5514 | 9.8 |
| Mars | 228.0 | 0.642 | -65 | 1.88 | 3934 | 3.7 |
| Jupiter | 778.5 | 1898 | -110 | 11.9 | 1326 | 24.7 |
| Saturn | 1432.0 | 568 | -140 | 29.4 | 687 | 9.0 |
| Uranus | 2867.0 | 86.8 | -195 | 83.8 | 1270 | 8.7 |
| Neptune | 4515.0 | 102 | -200 | 164 | 1638 | 11.0 |
| Sun | 5906.4 | 1,990,000 | 5,600 | 274 | 1408 | 5906.4 |
FOR YOUR INFORMATION
INFORMATION: GLOBAL POSITIONING SYSTEM (GPS)
Many applications of satellite technology affect our lives. An increasingly important application is the network of 24 satellites called the Global Positioning System (GPS), which can be used to determine the position of an object. Figure illustrates how the system works by locating the position of an enemy tank. A measurement using a single satellite locates the tank somewhere on a green circle, as shown in Figure (a). While a measurement using a second satellite locates the tank on another circle. The intersection of the circles reveals two possible positions for the tank, as shown in Figure (b). With the aid of a third satellite, a third circle can be established, which intersects the other two and identifies the tank's exact position, as shown in Figure (c).
