Sun

The Sun is a G-type main-sequence yellow dwarf star in the center of our solar system, and it is the largest, brightest and most massive object in the system. It is a ball of plasma and is the main source of radiant energy (solar power) and light.

The Sun formed around 4.5 billion years ago. As it grew, planets including Earth, moons and asteroids formed around it, bound in orbit to their parent star by its immense gravity.

The sun’s core reaches temperatures of 15 million degrees Celsius (C). The part of the sun that we see on Earth is the photosphere (surface) which ranges from around 3700 C to 7700 C. Above the photosphere is atmosphere of the sun known as the corona. The region of the sun between the photosphere and core is called the chromosphere, with temperatures around 500,000 C.

Nuclear fusion, in which it fuses hydrogen to create helium, powers the Sun, and the heat and light from this nuclear reaction enabled life on Earth to evolve and prosper. The ratio of the sun's mass is 73% hydrogen, 25% helium, and 2% metals.

The sun is around halfway through its main sequence of fusion. When the hydrogen is exhausted in around 5 billion years, the center of the sun will undergo a gravitational collapse, with its outer shells expanding outwards, becoming a red giant. It will then consume the inner planets, including Earth. These outer layers will be shed after about 1 billion years, exposing the Sun's collapsed core, which turns the Sun into a white dwarf.

It is presumed that after so many billion years, mankind will have found many ways to escape the death of the Sun:


 * Interstellar Ark or interstellar sprawl, spreading our species to other solar systems or beyond.
 * One or more technological singularities could lead to self-replicating nanobots taking over the solar system and even spreading far beyond.
 * Moving away from the Sun, or moving the Sun away from us, or delaying the decay, with a stellar engine.
 * Creating an artificial Sun, with somehow transferring its fuel to another stellar object.
 * Star lifting materials from its atmosphere and outer layers, dramatically extending its lifespan to trillions of years.