Space Rumors

A star is a massive, luminous ball of plasma that produces a tremendous amount of light and other forms of energy which is held together by gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth. Other stars are visible in the night sky, when they are not outshone by the Sun. The sun looks like a ball because it is much closer to Earth than any other star.

The sun and most other stars are made of gas and a hot, gas like substance known as plasma. But some stars, called white dwarfs and neutron stars, consist of tightly packed atoms or subatomic particles. These stars are therefore much denser than anything on Earth. For most of its life, a star shines due to thermonuclear fusion in its core releasing energy that traverses the star's interior and then radiates into outer space. Almost all elements heavier than hydrogen and helium were created by fusion processes in stars.

Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity and motion through space. The total mass of a star is the principal determinant in its evolution and eventual fate. Other characteristics of a star are determined by its evolutionary history, including the diameter, rotation, movement and temperature. A plot of the temperature of many stars against their luminosities, known as a Hertz sprung-Russell diagram (H–R diagram), allows the age and evolutionary state of a star to be determined.

About 75 percent of all stars are members of a binary system, a pair of closely spaced stars that orbit each other. The sun is not a member of a binary system. However, its nearest known stellar neighbor, Proxima Centauri, is part of a multiple-star system that also includes Alpha Centauri A and Alpha Centauri B. The distance from the sun to Proxima Centauri is more than 25 trillion miles (40 trillion kilometers). This distance is so great that light takes 4.2 years to travel between the two stars. Scientists say that Proxima Centauri is 4.2 light-years from the sun.

What is a light year? The distance that a ray of light travels in one year is known as a light year. Light is the fastest of all things known to man. A Danish astronomer, Olaus Roemer(1644-1710), first calculated the speed of light in 1676 as 1,86,000 miles(2,97,600kilo meters) per second. Later German born American physicist professor Albert Michelson (1852-1931) made a more accurate calculation of the speed of light as 1,86,284miles per second, for all practical purposes the speed of light is taken as 1,86,000miles per second. The distance covered by light at this speed in a year is about 6*10 ¹² miles or 9.6*10 ¹² (96,000,000,000,000) kilometers. This distance is one light year. The maximum width of our galaxy is 1,20,000 light years. Can you try to imagine such a huge formation?