In order to glean information about stars, astronomers analyze electromagnetic emissions, or the light, that reaches Earth. A spectroscope is basically a device that focuses a beam of light through a prism, which divides the light into characteristic colors that can then be seen using an eyepiece or screen. The resulting spectrum is used to determine the chemical composition of stars. The lines on the spectrum, or spectral lines, are associated with known elements. In 1868, an unknown element was discovered and given the name helium. It was almost thirty years before the element would be detected on Earth (McMillan, 2011). The accepted classification scheme is a combination of two, the Harvard system types stars based on …show more content…
For about another thirty million years, the star continues to contract and its central density, central temperature, and surface temperature increase; then it is a main sequence star where pressure and gravity are balanced and nuclear energy is being generated in the core. It takes forty to fifty million years for a star to reach this stage. The Sun is a main sequence star (McMillan, 2011). Stars spend approximately eighty percent of their lives on the main sequence before evolving into something else. A star leaves the Main Sequence when it has exhausted most of the hydrogen in its core, which causes it to lose equilibrium. It begins to contract again as radiation and thermal pressure decrease, and gravity dominates. Even though core hydrogen fusion ceases, energy is still generated in the core because of gravitational contraction. While the Main Sequence is the hydrogen core fusion stage, the first stage after the Main Sequence is the hydrogen shell fusion stage of a star’s life. During the hydrogen shell fusion stage, the nuclear fusion rate is considerably greater than during the Main Sequence. Changes in the outer layers of a star occur as the internal changes are happening. Increased pressure causes enormous expansion in the outer layers of the star, which leads to them cooling because they are farther away from the core. Visible
- Discuss stellar evolution (describing each stage in brief). What forces are opposing one another throughout the life of a star and how do they influence the various stages in the life cycle of a star
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
A protostar is a contracting cloud of gas and dust that contains enough mass to form a sun. Together, growing pressure and mass form both the protostar and the remaining star phases that will follow afterward. During the protostar phase, nuclear fusion begins. Nuclear fusion is the process in which atoms combine to create larger atoms. In a star, the nuclear fusion converts hydrogen into helium. This nuclear fusion in the protostar produced an outward force along with gravity. After this phase, the protostar becomes a main sequence
Stage 8 is when the star starts to run out of fuel. It has spent close to 10 billion years burning hydrogen in its core and now it’s starting to run low and almost empty of the fuel it requires to keep burning. As the hydrogen starts to run low, helium levels start to increase in the higher temperature core as well as on the surface. However, the surface helium isn’t as noticeable because it doesn’t burn as high or fast as the inner core. But as the hydrogen completely runs out, the nuclear fusion subsides and a core of non-burning helium grows, forcing the burning of the star to head out of the inner core and up to the outer core. At this point, the radius of the star starts to grow rapidly because of the gas pressure and the core shrinks under the pressure of gravity.
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
Stars generate energy via nuclear fusion of elements. Stars of the magnitude great enough to become type II supernovae possess the mass needed to fuse elements that have an atomic mass greater than hydrogen and helium. The energy generated by these fusion reactions is large enough that it is able to counter the force of gravity and prevent the star from collapsing, maintaining stellar equilibrium. The helium produced in the core builds
When we think of stars, we often think that they are all the same. We often think that they are all just big balls of gas burning up to billions of light years away. However, that isn't exactly true. The truth is that stars are very diverse. Just like anything else in our Universe, stars fall into many different classifications based on its defining characteristics. In this essay I will discuss several different types of stars.
Then, overtime the giants gasses drift away from the core then the gasses appear as a cloud around a dying sunlike star. When the clouds disperse, gravity causes the remaining matter in the core to collapse inward. The core becomes denser and very hot, then the star becomes a white dwarf. A white dwarf is the hot, dense core of matter that remains from the collapse of a low mass
After a star lives for about 1 million years, it becomes a main sequence star. Once it becomes a main sequence star, it will then go through a proton-proton chain reaction. Since the force of gravity goes inward, the force of fusion will then go outward from the core. This process will continue for about 10 billion years even when the star is "burning" Over those ten years, the stars will eventually slowly run out of hydrogen. After it runs out of hydrogen, the core will fill up with helium.
This is the fourth stage of a star’s life cycle. The Star diameter will be about 700,000 km. An average star will live for about 10 billion years in this stage. Our Sun is only about 5 billion years old. After the Infrared becomes a Star, it will continue to burn changing more of its Hydrogen into Helium. Eventually the Hydrogen begins to run out, until the Star becomes a Red Giant.
A star’s life cycle is determined by mass; the larger a star is, the shorter its lifespan is. When stars are formed, they begin as clouds of gas and dust in nebulae. Because of gravity, the matter condenses into a sphere where hydrogen is combined with helium, forming a protostar. As energy is released through nuclear fusion, stars enter the main sequence, the longest phase of a star’s life where it reaches stable nuclear reactions.
Once all of the hydrogen in the core of the sun is depleted, the sun begins its post main sequence by ascending the red giant branch, starting with a phenomenon known as shell burning. Once the hydrogen core is depleted, outward radiation pressure stops and “inward gravitational attraction causes the helium core to contract, converting gravitational potential energy into thermal energy” (http://www.atnf.csiro.au/outreach/education/senior/astrophysics/stellarevolution_postmain.html). This thermal energy causes an increase in temperature which heats up the hydrogen shell surrounding its core, and once a certain temperature is reached, hydrogen fusion occurs which produces more energy than when it was on the main sequence. Due to this increase in
The massive star begins its life with a giant molecular. Molecular cloud are made from mega collections of gay and dust. While going through it’s awkward stages of adolescence it spends a great doing of nuclear fusion, its fusing hydrogen into helium for a long time. For millions of years the star has so much fuel, hydrogen atoms that it does so much smashing a creating new elements and energy of all day and every minute.
Low Mass and High Mass stars start out from the same place and both evolve into Red giants. Although after that, Low Mass stars end up as white dwarfs. Big mass stars end up as Black Holes or Neutron Stars. Each phase of a star is a result of the star changing it’s