The Birth and Death of Stars
- Stars have existed for billions of years, and it is agreed that they follow a predicted life cycle however the path that each star follows is determined by the amount of matter that is gathered at the point of the 'birth' of the star. Stars are split into three major categories all according to their size. Those 3-5 times larger than our sun, those approximately our solar mass and those less than our sun.
Massive Stars ( giants)
Massive Stars are 3-5 times bigger than the size of our sun. They burn through their store of hydrogen extremely quick therefore meaning they have a much shorter life. They also have a very violent death.
Super Red Giant:
A super red giant is extremely large and it usually has a minimum of fifteen solar masses.
The super red giant will eventually collapse into what is known as a super nova. This is a large explosion of most of the material in the star. The result of this is a large, bright mass that emits great amounts energy. After the super nova either a black hole or a neutron star can occur.
A black hole is a large abyss or area of space-time with a gravitational field so intense that its escape velocity is equal to or exceeds the speed of light.
A neutron star is a cosmic mass consisting of the remains of a massive star which are very dense. This mass has only neutrons left and therefore having a very powerful gravitational pull.
RED GIANTSA red giant is a star that produces are fair amount of light due to their immense size. All medium stars pass through this stage during their life time. It occurs because the star's core is beginning to run out of hydrogen and eventually the core becomes so hot that helium is turned into carbon, this causes the outer layers of the star to expand. As it cools it turns red. Red Giants are about 10 - 1500 times larger than our sun and appear to be red.
When a stars energy store has completely run out, all the nuclear reactions stop and the gravitational collapse continues. the outer layers of the star expand, forming a planetary nebula which orbits around the remains of the core. It will continue dimming down and cooling until all of its heat energy is gone. White dwarfs have a low luminosity and a mass that is similar to our sun. Also they are extremely dense.
A brown dwarf is a celestial body that looks like a star however it can not emit any light at all because it is to small to ignite nuclear fusion. New brown dwarfs are hotter than older ones; the core of a brown dwarf is less than three million degrees Kelvin (726.85 degrees Celsius). They are also below 0.8 solar masses. Although the name of the star states that it is brown, the star is actually red . After the life cycle of a brown dwarf is complete it becomes a black dwarf.
A black dwarf is a white dwarf that has cooled down to the same temperature as cosmic microwave background radiation. It is also invisible because as a white dwarf it was only shining when it was still hot. Once it has cooled down and become a black dwarf it no longer has heat or a power source to make it shine. It can take hundreds of billions of years to cool down completely so after this stage is competed the star just fades away.
What is the difference between massive stars and small stars?
There are many things that differ a massive star to a small star. Firstly they both have extremely different life cycles, especially when they 'die'.The life cycle of a massive star is different to a small stars because unlike a small star, it doesn't become a red giant but it fuses into a red super giant. From there it explodes into a supernova becoming either a black hole or a neutron star. Unlike the small star that first becomes a planetary nebula after the red giant, finally becoming a white dwarf then a brown dwarf. Obviously the size of these two stars are immensely different as a massive star is 3-5 our solar mass however a small star is less than a solar mass.
This is a HR diagram displaying the temperature and absolute magnitude of the star.