Star Life Cycle Essay

After its core hydrogen is depleted, a red main sequence star will go supernova after its red giant phase.

The life cycle of the Sun starts like all stars with a cloud of dust and gas made up of mostly hydrogen. If the cloud cools, it will shrink because of the gravitational pull between the particles

As this slow contraction continues, the core temperature, density, and pressure of the star continues to increase. As the star shrinks it becomes so dense that it starts to compress helium. This results in the star to swell due to the hot core and leaving a relatively cool surface. Eventually the outer layers of the star expand outwards, increasing the size of the star. As the layers continue to expand, the surface temperature continues to cool, forming a relatively large star called a red giant.

Comparing red giants to the sun, they are about 1000 times larger. Compared to the sun’s temperature, a red giants temperature is about half as much. This is because the same amount of energy has to be spread out across a much more massive star causing it to be cooler than it was before. The name red giant was given to these stars because the change in temperature causes the star to shine in the redder part of the spectrum. Stars can spend anywhere between 1000 years and one billion years in the red giant phase. After a certain amount of time, the helium finally runs out and fusion stops. Since there is no more helium, gravity pushes the star inward. The stars outer atmosphere is then blown out into huge clouds of gas and dust which is known as planetary nebulae. These clouds of gas and dust are then made to make new stars. As for the core of the star, it is still there. The star is now a white dwarf. White dwarf stars occur when the red giant loses its outer atmosphere. White dwarf stars are extremely hot because they are composed of only the core of the star which is the hottest

The larger a star, the shorter their lifespan is, and they explode as supernovae, blasting out powerful shockwaves that create a chain-reaction that spews throughout the galaxy. Within just a few million years, the galaxy is forming stars up to hundreds of times more than a normal galaxy would. When all of the gas available is used up in about ten million years, the galaxy calms down and the period

Planetary nebula are formed in the outer core of the star that are vanished when the star of the Sun’s mass changes from a red giant to white dwarf. At this stage all the energy from the star fades away losing layers and forms a complex structure.

Stars, such as our sun begin their life in an entirely different form from the one we come to recognize. Their lives begin in the bitter cold, around 10 degrees Kelvin, which is only a few degrees above the 3 degrees Kelvin temperature of the background of space itself. Their density is also extremely sparse, with a density of around 1 billion particles per cubic metre, which is only a wisp in comparison to the density of around 1410 kilograms per cubic metre that the sun like star will have during its time on the main sequence. Although they may be quite low in density, the clouds are absolutely enormous, spanning up to tens of parsecs (an astronomical unit of measurement that is determined to be around 19 trillion miles) across. In these clouds, there is an abundance of molecular and atomic gases of various types, which will serve as the rough material that will be used to create the stars and solar systems. Hydrogen is the most abundant element found within these clouds, although they can also contain many other trace elements of metals and gasses.

What is left after the huge explosion is another dwarf star, a neutron star, or the fierce black hole. A neutron star is about the size of a city like Los Angeles, but has the mass of about two suns. This means it is incredibly dense and has an unbelievable gravitational pull, almost 2 billion times that on earth. In fact, this pull is so strong that it bends radiation and allows astronomers to see the back of the star. They also spin up to 48 thousand times per minute due to the energy from the supernova.

It is now a Red Giant after about 100 million years. The luminosity of the star has increased to around 100 Sols while still having a tiny core which is about a quarter of the mass of the star.

After approximately 10 billion years after the star is considered to be a main sequence star, the hydrogen at the center of the core is depleted. This causes the nuclear fusion which had been previously fueling the star to die out. Helium replaces the hydrogen in the core, and the inner core begins to shrink due to gravity. This process speeds up once all the hydrogen is completely used up. The radius of the star has increased

All stars are born in nebulae. Nebulae are huge cold clouds of gas and dust. The formation of protostars requires huge clouds of gas and dust collapsing under gravitational forces. The stage of a protostar last an approximate of 50 million years. As stars grow, they also expand. When the core runs out of hydrogen and helium, the contacts and outer layers of the core expand, become cold, and the brightness decreases. This is also known as a Red Giant or a Red Supergiant which mainly consists of the star’s mass. After a while of beginning the process of its death it goes through other stages.

Once its 10 billion years of burning comes to an end, the hydrogen that it has been using as a fuel source has, for the most part, depleted. The center of the star begins to increase in size as the production of helium increases and an inner core of helium starts to grow. The helium does not burn at these temperatures so the burning is moved out to higher layers. This inner core begins to shrink under the force of gravity and while the star is extremely hot, it is still too cool to fuse helium. The burning of hydrogen in the outer layers, however, increases and the radius of the star increases nearly three times, bringing the star out of Main Sequence section and into the category of subgiant.

A star is born in a high-density nebula and condenses into gas and dust and contracts under its own gravity. Next, a region of condensing matter will begin to heat up and star to glow, forming protostars. The temperature at this point is 5 million degrees centigrade. When this temperature is reached, hydrogen fuses and forms helium. A star then begins to release energy which causes it to contract and shine. After millions of years, the core of the star which is helium, contracts and a reaction begins to occur in a shell around the core. The core is at a high enough temperature for helium to form into carbon and the out layer of the star expands, cools and becomes less bright. The core then burns out and the outer layer leaves the core as a gaseous shell. The rest of the core cools and becomes a white dwarf and is less bright. When the white dwarf stops shining, it is called a black dwarf.

These two masses go through a similar process. High Mass Stars are born from the Stellar Nebula,(just like the Low Mass stars), and become a star although they are a lot bigger than them. They too become Red Giants, but as Red Supergiants. After becoming a Red Supergiant, there is a distinction. High Mass stars go through a phase called Supernova. A Supernova happens when a star runs out of nuclear fuel, making its mass seep through into it’s core. Soon enough, the core gets too heavy it can’t withstand its own gravitational pull so it collapses. This results in an enormous explosion. After the Supernova, there are two things a High Mass star ends up as. A Black Hole or a Neutron Star. A Black hole is like a gravitational vacuum. It sucks up matter, radiation, and even light. So much matter clumped in a tiny space makes the Black hole extremely powerful. A Neutron star is formed after the explosion, when the stars outer layer blows apart in a spectacular display. It leaves a small, dense core that continues to diminish. Protons and electrons are packed tightly by gravity, producing the

Main sequence stars like our own sun enduring in a state of nuclear fusion during which they will produce energy for billions of years by replacing hydrogen to helium. Stars change over billions of years. When their main sequence phase ends they pass through other states of existence according to their size and other characteristics. The larger a star's mass, the shorter its lifespan is. As stars move toward the end of their lives, much of their hydrogen will be converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell to expand. These large, puffy stars are known as Red Giants. The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a White Dwarf. White dwarfs cool down for billions and billions of years, until they finally go dark and produce no energy at all. Once this happens, scientists have yet to observe, such stars become known as Black Dwarfs. A few stars avoid this evolutionary path and instead go out with a bang, exploding as Supernovae. These violent explosions leave behind a small core that will then turn into something called a Neutron Star or even, if the remainder is large enough, it is then turned into something called a Black Hole.