Sun

Properties:

Mass: 1.9885* 10³⁰ kg

Age: 4.6B years

Radius: 695,700 km

Effective Temperature(Photosphere): 5,772 K

Luminosity: 3.828*10²⁶ W

Etymology: Sunne(Old English)

The Sun is the star that most of the Solar System orbit around. It is currently a main-sequence star as it is able to undergo nuclear fusion sustainably, which releases radiant energy in the form of electromagnetic radiation in the visible light portion of the spectrum.

​

The corona of the Sun(or any star for that matter) is the aura of plasma that surrounds the Sun. On the image above, the corona is the outer edges of the star giving it a "glow". This portion of the Sun is quite visible during a total solar eclipse because when the moon covers the Sun from our relative point of view, you can still view the corona of the Sun on its outer edges. The corona is primarily composed of plasma particles with a relatively low density. The temperatures of the plasma far exceed the Sun's surface temperature as they reach over 1,000,000 Kelvin. Lastly, the composition of the corona is mainly hydrogenous(H), like in the core. However, due to the extreme temperatures found here, much of the hydrogen in the corona ionizes and there is a slight composition of iron(Fe), too.

​

The corona is also responsible for solar wind, which is the stream of charged particles from the corona. These particles include electrons, protons, and other alpha particles along with atomic nuclei. If the solar wind reaches Earth, it can cause disturbances in the Earth's geomagnetic field and cause the solar wind, mainly the electrons and protons, to ionize and excite in the upper atmosphere of Earth. This causes lots of light to emit as a result, forming what we know as auroras.

​

After solar flares, which are mass bursts of electromagnetic radiation from the Sun, a phenomenon known as a CME(coronal mass ejection) occurs, and huge streams of plasma eject from the corona. The plasma often collides into the solar wind stream of particles

​​

The chromosphere of the Sun is the layer in between the photosphere and the corona. The bottom of this layer is known as the temperature minimum, which has temperatures around 3800 K. The chromosphere is the only main layer of the Sun whose temperature increases as you go farther from the Sun's core. This seems paradoxical because this doesn't occur in any other layer of the Sun but it is believed to be due to something known as magnetic reconnection. Magnetic reconnection is a complex process in its own right but its effects are simple. It causes magnetic energy in the chromosphere to convert to kinetic energy and thermal energy, causing the temperatures to increase when altitude increases.

The photosphere of the Sun is the outer shell of the Sun that emits light. It looks very bubbly due to an effect known as solar granulation, where the arrangements of plasma in the photosphere look bubbly in nature. This is due to the convection caused by heat in the Sun's core. The Sun is effectively "boiling" just like a metal pan. This means that heat from the bottom of the pan(analogous to the Sun's core) eventually reaches the surroundings(photosphere) through convection and causes "bubbles" to form if the pan is filled with, say, water. An image of solar granulation is shown above. ​ These aren't all of the layers of the Sun but they are the most well-researched because most of what is known about the layers deeper inside the Sun is highly inferential and not detailed nor simple.