Explain the similarities and differences between small and high mass star life cycles in terms of forces and energy.


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Low mass stars and high mass stars share similarities and differences.  One of the similarities is they both start the same way, with a huge collection of gases, primarily hydrogen and helium.  Another similarity would be the way they generate their energy, through a process known as nuclear fusion.  Under extreme pressure and high temperature, two hydrogen nuclei fuse together to form a helium nucleus.  Energy is released in this process.  Over the small star's lifetime, the core shrinks as the hydrogen is converted to helium, while the outer envelope of gases expand into what is known as a red giant.  Small stars rotate, sometimes very quickly, producing solar eruptions of x-rays.The core continues to get hotter, converting helium nuclei to carbon, the end product.  Temperatures may get as high as 100 million degrees Kelvin in this process.  Eventually, the remaining gases are ejected from the core, due to low gravity, resulting in a circular effect known as a planetary nebula.  The carbon core cools, first into a white dwarf, then a black dwarf.  The material from a white dwarf is extremely dense, a small amount (teaspoon) brought back to earth would weigh tons.

The differences between the small mass star and high mass star are not as numerous as the similarities.  The primary difference is the amount of time it takes for the nuclear fusion to occur.  The above described nuclear fusion process happens at a much faster progression, resulting in higher temperatures, pressure, and conversion to other elemental products, such as carbon, then nitrogen, then oxygen.  Ultimately, the oxygen gets converted to silicon, then silicon to iron, the terminal star element.  There is also enough gravity to hold the outer gas layers in to the star's core, so it is not ejected as it is in a small mass star.

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