The axis of rotation passes into and out of the body at two points known as the north (N) and south (S) poles.Ī celestial body may also move around another in a closed path called an orbit. This spinning motion is called rotation (see Fig. (Adapted from: Purdue University, Theory of Tropics)Ī celestial body spins around an imaginary line through itself called an axis. , or 9.46 trillion kilometers! Thus, 1 ly = 9.46 × 10 12 km Celestial Bodies Rotation and Revolutionįig 1: Rotation. Since there are 86400 seconds in a day, and there are 365 days in a year, a light year equals The distance that a light beam can travel in a year is known as a light-year ( ly). This is equivalent to light being able to circle the Earth seven times in one second! Accordingly, light-second ( light-sec), a unit of distance, is defined as 1 light-sec = 300000 km The speed of light is the greatest speed that can be attained by any material object in the universe, and is about 300000 km / s. Instead, distances in space are measured using the speed of light. The size of the universe is so beyond human comprehension that the common units of distance, like the kilometer, make little utility sense. The universe, in effect, is mostly empty space. The space, along with the celestial bodies, make up what we call the Universe. They are separated from each other by immense regions of emptiness called space. The Universe - 01 Celestial Bodies & the UniverseĪll astronomical objects in the sky, such as the Sun, the Moon and the stars, are collectively known as celestial bodies. The page has been upgraded to a new home.
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