An introduction to the Sun
The Sun is our star, and is the most massive object within our solar system (which is the Sun, the planets and all the other objects within its gravitational sphere of influence). More than 99.9% of the matter within the solar system is in the Sun.
The Sun was formed about 4.5billion years ago when part of a giant molecular cloud, a nebula, gravitationally collapsed and formed a number of stars, our Sun being one of them. Our proto-star(s) collapsed under self-gravitation and the pressure and temperature increased in it's core until sufficiently high enough for nuclear fusion reactions to start.
The Sun generates its energy by nuclear fusion but the Sun is stable and in balance, it doesn’t explode! The internal pressures are balanced by the gravitational potential (gravitational self-collapse). It is said to be in Hydrostatic equilibrium.
Energy is transported from the core by radiation and convection processes and to the Earth across the vacuum of space by radiation. Within the Sun, currently, conduction is almost irrelevant.
The Sun is our star, and is the most massive object within our solar system (which is the Sun, the planets and all the other objects within its gravitational sphere of influence). More than 99.9% of the matter within the solar system is in the Sun.
The Sun was formed about 4.5billion years ago when part of a giant molecular cloud, a nebula, gravitationally collapsed and formed a number of stars, our Sun being one of them. Our proto-star(s) collapsed under self-gravitation and the pressure and temperature increased in it's core until sufficiently high enough for nuclear fusion reactions to start.
The Sun generates its energy by nuclear fusion but the Sun is stable and in balance, it doesn’t explode! The internal pressures are balanced by the gravitational potential (gravitational self-collapse). It is said to be in Hydrostatic equilibrium.
Energy is transported from the core by radiation and convection processes and to the Earth across the vacuum of space by radiation. Within the Sun, currently, conduction is almost irrelevant.
The Sun is a massive sphere of gas and plasma. Although we can see an apparent ‘surface’ to the sun, which we call the photosphere, it has no distinct surface. We can see features on the photosphere, predominately the granulation (which is an effect of convection processes) and Sun spots (which are caused by rotational disruptions in the Sun’s bi polar magnetic field.
Above the photosphere the lower atmosphere is called the Chromosphere and the higher and outer regions are called the Corona. Eruptive features seen linking the photosphere and the Corona, and beyond.
These include spicules, prominences, the (highly energised) flares, and material can be ejected from the sun via CMEs – Coronal mass ejections.
These include spicules, prominences, the (highly energised) flares, and material can be ejected from the sun via CMEs – Coronal mass ejections.
Space Weather, the radiation and particle flows within the solar system and critically important for satellites, probes and human space exploration, is dependent upon flares and CMEs, but also the solar wind – a continual, but varying, slow of high velocity atomic particles.

The Sun will stay in its current state for about another 5 billion years. After this time, the available hydrogen used to 'power' the Sun will all be used up, and dramatic changes will begin. The Sun will undertake a series of large scale radial pulsations and oscillations.
It will, for a relatively short time become a 'red-giant' star, and, if life on Earth had not already perished through the large variations in incident radiation, all life will become extinguished as the Earth will likely be fully consumed within the then hugely expanded size of the Sun.
Ultimately, it’s fate will be to form a temporary planetary nebula and a more permanent white dwarf star.
But don't worry, we have a few billion years before any of this happens!
It will, for a relatively short time become a 'red-giant' star, and, if life on Earth had not already perished through the large variations in incident radiation, all life will become extinguished as the Earth will likely be fully consumed within the then hugely expanded size of the Sun.
Ultimately, it’s fate will be to form a temporary planetary nebula and a more permanent white dwarf star.
But don't worry, we have a few billion years before any of this happens!
All images used on this page are courtesy, and copyright, of ESO (Pleiades cluster) and NASA respectively.