Star is a cluster of hot gas, usually hydrogen and helium, which emits light and heat due to what is happening in her nuclear and thermonuclear reactions.
The closest star to our Sun, the nearest star to our solar system is located at a distance of 4.5 light years (the distance that light travels in one year) from the Earth.
By earthly standards, it is a huge figure.
The study of humanity was engaged with starsancient times. The research results are used to navigate sailors and timing. Until recently, the main instrument of astronomers were simply telescopes that allowed to watch the stars. Today, in addition to studying the stars of conventional optical telescopes, radio telescopes are used, that register is not visible light, stars, and coming from her electromagnetic radiation. Radio telescope lets you explore the stars, at a distance much greater than the limit of the reach of optical telescopes.
We should also mention the orbital telescope "Hubble", which allowed to observe, which does not interfere with the Earth and the adverse weather conditions of the atmosphere.
In addition to optical and radio telescopes, astronomersis used for viewing the stars special photo equipment, which photographed large areas of the sky with large exposures. Slow shutter speed allows radiation from the faint stars to accumulate, which further makes them visible in the pictures. Photos are used later to search for new stars, which can not be detected in other ways, because their radiation is too weak.
Another very important way to study the starsa spectral analysis. With the help of spectral analysis, scientists can determine the temperature on the surface of the star, the chemical composition of stellar matter and the nature of its movement in the universe. All the stars are divided into spectral classes, one class stars have the same color. This color can vary from red to blue. From the colors of the spectrum depends on temperature of the star: the hottest blue stars, the surface temperature of 25,000 degrees begins, red stars are the coldest, their temperature usually does not exceed 1600 degrees. To determine the presence of a chemical element in the star can be compared with the spectrum of an element of the star spectrum. Helium and hydrogen, the elements that make up the stars, and there are on Earth.</ P>