Fusion - the basis of the existence of stars
Because of thermonuclear fusion reactions inside stars temperature can reach millions of degrees Kelvin - that is where there is a transformation of hydrogen into helium and releases massive amounts of energy that comes to us in the form of light.On the surface temperature decreases star several orders of magnitude.
stars are visible from space about the same as with the Earth's surface, with one exception - the atmosphere of the planet scatters the light, so the observer who is in orbit, the stars shine brighter.Color star when viewed from the space remains the same as in the observation from the ground, with only a few exceptions.The true color of the stars, in which the hydrogen is almost "burnt out" and the temperature droppe
d to 2000-5000 degrees Kelvin, is different from the observed.Yellowish-orange stars of spectral type "K" actually have orange and orange-red star of class "M" - Red.
size and shape of stars
stars are very large.For example, the Sun weighs as much as 332 thousand weigh the planets with the same mass as the Earth.If you add up the weight of all celestial bodies located in our solar system - their weight compared to the mass of the Sun will be of a percent.
It is believed that the shape of the stars constant.But in fact it is changing.For example, the diameter of the sun each day is reduced by twenty meters.There is another interesting fact - it turns out, the sun is pulsating.With time period of 2 hours 40 minutes The surface of the star expands and then contracts a rate of about seven kilometers per hour.
near the sun looks like a huge glowing ball on its surface and then there are prominences - emissions of dense matter, which are held on the surface of a star due to the magnetic field.
Not all stars - as big as the sun.For example, there are white dwarfs, whose size is one hundred times or more less than the diameter of the sun.The mass comparable to the mass of the Sun, a star much substance in them sealed.
There are stars whose diameter may exceed the diameter of the sun hundreds of times.They are called red giants.There is a theory of the life cycle of stars, according to which our Sun in several billion years, too, will become a red giant and increase in size so that it reaches the surface of the Earth's orbit.