When looking at stars from the surface of the Earth, they seem to form groups or constellations.

The closest star to us (aside from the Sun) is Proxima Centauri, which is over 4,2 light years away from planet Earth. It is too dim to distinguish with the naked eye. The brightest star in the night sky is Sirius, which is 8,7 light years away from Earth. 

However, the star that is nearest to us is actually the Sun. It is a burning ball of gas over a million kilometers in size. The distance between the Earth and the Sun is approximately 150 000 (150 million) kilometers. The Sun was formed just under five billion years ago, making it a relatively young star.

When the Sun's fuel, hydrogen, eventually runs out, the Sun will expand into a red giant, swallowing the closest planets of our solar system, Mercury and Venus, and making the conditions on planet Earth extremely hot. When the outernmost layers of the sun are finally blown into space, it will shrink and form a white dwarf. 

The video below shows activity on the surface of the Sun. The nuclear reactions that take place inside the star produce an enormous amount of energy, which is manifested as great flares on the star's surface.

​​​