Another neat form of E/c2 is in the form of our sun…
Nuclear fusion, the source of all the energy so generously radiated by the Sun, does two things: it converts hydrogen into helium (or rather, makes helium nuclei from protons) and it converts mass to energy.
The mass-to-energy conversion is described by Einstein's famous equation: E = mc2, or, in words, energy equals mass times the square of the
velocity of light. Because the velocity of light is a very large number, this equation says that lots of energy can be gained from using up a modest amount of mass.
The energy created by the fusion processes within the core of the Sun (or any other star) exerts an outward pressure. Unless contained, such pressure would produce an explosion (as happens in the hydrogen bomb, on a much smaller scale). The inward pressure that keeps a star from exploding is the
gravitational attraction of the gas
mantle surrounding the core (which is most of the volume of the Sun, and is very hot but does not burn itself). -
http://earthguide.ucsd.edu/virtualmuseum/ita/07_2.shtml
Nuclear fusion produces much more power than fission. China has a fusion reactor that is supposed to come online in 2025 that boasts of producing many times the heat of the sun -
China's $1 trillion 'artificial sun' fusion reactor just got five times hotter than the sun