A Mystery of Space: S T A R S- [What is a Star?]

A star is a large mass of hot gases emitting energy waves. The waves are mostly light, which result from nuclear reactions (inside the star). The outside of a star is made up of a layer of hot gases (photosphere), surrounded by what looks like a ring of light (corona), and then an outflowing stream of particles (solar wind). Scientists only have a vague idea of what is inside a star, which they think contain layers, increasing in density and temperature until the core is reached, where there are thermonuclear reactions.
When you look up into the sky on a clear night, you may have tried to count the stars. But there were so many, you probably gave up. In our galaxy, the Milky Way, there are

Milky Way Galaxy

hundreds of billions of stars. To give you a good idea, we can only see (with a telescope) about 400 million galaxies (which, if they are similar to ours, then they each would have about 400 billion stars in them, which adds up to 160,000,000,000,000,000,000 stars!).
The star closest to the earth, Proxima Centauri (also known as Alpha Centauri C) which is actually part of a triple-star system, is about 25,100,000,000,000 miles, or 40,700,000,000,000 kilometers from us. This equals 4.27 light-years.