the sun

The star around which the Earth revolves, and the planet's source of light and heat, hence life. The Sun is a globe of gas, 1.4 × 106 km in diameter with a mass 333,000 times the Earth, held together by its own gravity. The surface temp of the Sun is about 6000 K; since solids and liquids do not exist at these temp, the Sun is entirely gaseous. Almost all the gas is in atomic form, although a few molecules exist in the coolest surface regions, such as sunspots.
The Sun is a typical member of the spectral class dG2, stars of surface temp 6000 K. The d stands for a dwarf, a normal star of that class.

Solar structure
The interior of the Sun can be studied only by inference from the observed properties of the entire star. The great mass of the Sun presses down on the center, requiring a gas with a central density of near 90 g/cm3 and 2 × 107 K temperature to support it. At these huge temp and densities, nuclear reactions take place. The radiation produced flows outward till it is radiated into space by the surface (photosphere) at 6000 K.

Energy production
The energy of the Sun is produced by the conversion of hydrogen into helium. For each hydrogen atom converted, one neutrino is produced. These neutrinos are detected, but less than the expected number.

Convection
In the outer regions of the solar interior, the temp is low enough for ions and even neutral atoms to form and, as a result, atomic absorption becomes very important. The high opacity makes it very difficult for the radiation to continue outward, so steep temp gradients are established that result in convective currents. Most of the outer envelope of the Sun is in such convective equilibrium. These large-scale mass motions are responsible for the complex phenomena observed at the surface.

Radiation
Electromagnetic energy is produced by the Sun in essentially all wavelengths. However, more than 95% of the energy is concentrated in the relatively narrow band between 290 and 2500 nm and is accessible to routine observation from ground stations on Earth. The maximum radiation is in the green region, and the eyes of human beings have naturally evolved to be sensitive to this range of the spectrum. The total radiation is called the solar constant. It is not exactly constant but varies slightly (±0.1%) with the solar cycle. The ultraviolet flux, however, varies by substantial factors depending on the exact wavelength, and this affects the Earth's upper atmosphere.

Atmosphere
Although the Sun is gaseous, it can be seen only to the point at which the density is so high that the material is opaque. This layer, the visible surface of the Sun, is termed the photosphere. Light from father down reaches the Earth by repeated absorption and emission by the atoms, but the deepest layers cannot be seen directly. The surface is actually not sharp, but the Sun is so far away that the smallest distance that can be resolved with the best telescope is about 300 km. Since the density e-folding height (scale height) is less than 200 km, the edge appears sharp.

Coronal holes
Early coronal observations showed that the corona was occasionally absent over certain regions. In particular, at sunspot minimum it was quite weak over the poles. X-ray pictures revealed great bands of the solar surface essentially devoid of corona for many months. These proved to be regions where the local magnetic fields were connected to quite distant places, so the fields actually reached out to heights from which the solar wind could sweep the gas outward. Analysis of solar wind data showed that equatorial coronal holes were associated with high-velocity streams in the solar wind, and recurrent geomagnetic storms were associated with the return of these holes. The intensity is partly due to their strong, closed magnetic fields which trap the coronal gas.

Solar activity is a number of transient phenomena all connected with sunspots.
I hope this can help with your understanding. =)

the sun is hot, I love sunshine, do you?