STARS

So I'm going to be publishing a series of articles on stars starting now.

What is a Star?

Well,  according to Wikipedia,  the answer to that question is "A star is a luminous sphere of plasma held together by its own gravity"

I would define it as an entity which is forced to consume itself in order to exist. Basically,  it cannot be a star if it doesn't undertake nuclear fusion using gases which it is composed of.

How do stars work?

Well, in the simplest of terms, due to the heavy mass, temperature and pressure in the core, the hydrogen atoms are ripped off their electrons, and are squeezed to such an extent, that their protons fuse forming Helium producing a LOT of heat and light in the process. Fusion continues to happen until they run out of Hydrogen to fuse, but if they are massive enough, they can fuse helium too and this goes on until they eventually 'die', we'll cover that soon. Now to understand this better, lets take the example of the sun.

The Sun:

How does the sun run?

The sun is massive -1.989 x 10^30 kg. That is such a massive number that you could very well fit a few million Earths in it! It contains 2 OCTILLION TONS of gas[mostly Hydrogen]. The pressure at the sun's core is a staggering 250 BILLION times the pressure on you in the Earth. In comparison to other stars, it's still in the top 10% of stars, classifying them by their populations, but if you look directly at the size, the sun is somewhere in the lower middle of the spectrum.

The innermost layer of the sun is the core. The pressure at its core is an immense 1 billion times the pressure on you in the Earth. This core is mainly composed of hydrogen gas. At this pressure,  the temperature in the suns core is a staggering 15 million degrees celsius!  At this temperature and pressure,  the electron is ripped off the hydrogen,  and the protons are squeezed so hard together that an event I would say is the root cause of all life happens-they fuse and form Helium. Every second, the sun converts 800 tons of hydrogen into 790 tons of Helium, the remaining 10 tons are released as energy. The energy released is enormous- enough to power a STAR. An unimaginable amount of energy is released in the form of heat and light,  enough even to supply and support life on a planet which is 149 million km away. The energy released is the equivalent of millions of times the entire nuclear arsenal present on Earth and this happens every single second, I repeat every single second. So much for the Tsar Bomba.

 The energy released heats up the gas above the core, however not enough to fuse Hydrogen above the core. Hot air rises due to convection. It then cools and sinks back to the core. This layer is known as the convective layer.

Above this, is the photosphere. The density here makes the layer transparent, completely allowing light to pass through. After this, it travels and reaches us!

Above the photosphere is the corona or the solar wind. This extends for millions of kilometers! This basically is like a torrent of subatomic particles flooding the nearby space. It travels on average at a speed which is around 0.01% the speed of light, and can reach even higher! And mind you that is NOT a small number. It is equivalent to 277777.778 m/s!

Also, the light which reaches you, has to make it's way from the sun's core. The way this works is, a photon of a certain energy moves and strikes the next photon, losing some energy in the process, until eventually it breaks free from the sun to roam into space. This is a LONG process, and recent calculations show this takes around 250,000 years, around the same time early men roamed the Earth!

Another key, key feature regarding the sun is magnetism. I mentioned earlier that conditions inside the sun are so hot, they rip the electrons from the Hydrogen atoms. This group of negatively charged particles is called plasma. By Maxwell's Theory of Electromagnetism[in simple terms, a charged particle generates a magnetic field], sun has a magnetic field. The sun's rotation, along with convection, moves around plasma and creates this magnetic field. When plasma reaches the sun's surface[the photosphere], it cools. Some of these multiple magnetic fields generated by plasma, may get tangled up, thus preventing it from sinking down the sun's core. Due to it cooling, it loses it shine, producing a dark spot on the surface of the sun, something which is known as a sunspot.

Plasma also moves along these magnetic fields, creating large arches known as a prominence. It still is a mystery, and we don't understand this fully, but will do so in the future. 

Magnetic fields can also get interlocked, and sometimes as they contain a LOT of energy, they can even snap. All the energy which is stored now expands outwards in an explosive way, an event that is perilous and is known as a solar flare. These are mind-blowingly powerful, with the stronger ones emitting even 5-15% the entire net energy the sun emits! 

The blast of debris ejected during a solar flare can even hit the Earth, causing immense effects. Our atmosphere, coupled with our magnetic field reduces the high intensity light along with deflecting the electrons ejected. In most cases that is. But sometimes, the Earth's magnetic field interacts with the magnetic field causing an aurora at the Northern and Southern Poles, also known as the Northern and Southern Lights. The exact details as to why this occurs is still a mystery though. And these lights form multiple shapes, depending on the magnetic field's shape. BUT, there are a lot of disadvantages.  As the magnetic fields interact, they produce an EMP[electromagnetic pulse] which overloads power grids, causiing blackouts in mass. In 2012, a huge such event was detected and luckily for us, it missed the Earth. Had this hit us, it would've caused blackouts in many areas, apart from frying circuits of most satellites.

Another type of a solar flare is a CME[Coronal Mass Ejection] and this well, is HUGE, and unlike a solar flare is not localised as they occur higher in the surface of the sun! 

So this is basically how the sun goes about its daily business, it eats itself and every now and then ejects a lot of subatomic particles!