Properties of the Sun. Animation of the location in the night sky and the properties of the Sun (Sol), a yellow G-type star Sun that is 8 light minutes from Earth and the source of the energy that sustains all life on Earth. Here, the Sun is shown passing through the zodiacal constellation of Taurus. The Sun is a main sequence star. It is over 1.3 million kilometres across with a mass of around 2 million trillion trillion kilograms. The Sun formed around 4.5 billion years ago and will remain stable for another four billion years, at which point it will become a red giant. The Sun is spectral type G2, with a luminosity class of V. It radiates energy due to nuclear fusion in its core, with the energy released equivalent to 400 trillion trillion watts. The Sun has an atmospheric temperature of 5778 Kelvin. Its spectrum has neutral and ionized metal lines, especially ionized calcium lines.