star cluster. The former star cluster has disintegrated over time so that the Sun now orbits the centre of the Milky Way unbound to any other star. The dimensions of the Sun are truly amazing: it has a radius of 1.4 million km (109 times that of Earth), 12000 times the surface area of Earth, 333 000 times Earth's mass and 1.3 million times its volume... quite impressive if you consider the size of Earth itself.
The Sun is basically a very big ball of gas and plasma with a temperature of 15 million °C and a pressure of 200 billion bar in its core; perfect conditions to fuse hydrogen into helium. This process converts mass into energy very efficiently: every square metre of the Sun’s surface emits more than 63 megawatts of energy! Our article about stars explains the birth, life and death of a star in more detail.