Stars like the sun are fueled by the fusion of hydrogen atoms into helium. As a star exhausts its core hydrogen fuel supply, it becomes progressively more difficult to fuse hydrogen atoms together. The final step is when the star reaches a point where no more hydrogen can be fused and the star collapses in on itself. This process is called mass-loss, and it’s what happens when a main-sequence star runs out of hydrogen.
A massive star is an extremely luminous object with a diameter greater than 10 solar radii. A large star has a surface temperature of between 100,000 and 200,000 Kelvin. The sun is a G2V yellow dwarf star that is approximately 5 billion years old. Massive stars are born from molecular clouds, and when they exhaust their core hydrogen fuel, they begin to expand, eventually becoming red giants and, finally, supernovae.
The end of a massive star’s life begins when the core becomes hot enough that it undergoes thermonuclear fusion, creating a tremendous amount of energy. After about 15 seconds, the temperature reaches 14.1 million degrees Celsius, and nuclear burning occurs throughout the core. The core collapses, but the collapse is not symmetrical, and the core does not explode. Instead, the pressure builds, and the star expands, growing larger than 10 solar radii. The star continues to burn the helium that remains in the core, and the outer layers expand and cool rapidly. The star then becomes a red giant.
After about five billion years, the star explodes in a supernova. The shock wave from the supernova blast is called a stellar wind. This wind blows away material from the star, and the leftover debris forms a new, smaller star. The star that is formed by the debris is known as a planetary nebula, and it often resembles a comet. The original star is sometimes visible, although the star is now much fainter.
A main-sequence star exhausts its core hydrogen fuel supply by the process of nuclear fusion.
Main-sequence stars are those stars with a mass less than about 10 times the mass of our Sun.
After this, the star goes through two processes – hydrogen burning and helium burning. This can happen at different rates, depending on the exact star.
First, the star begins to expand.
The expanding star will burn hydrogen fuel in the core and produce energy that pushes it outward.
However, the star continues to fuse helium in its core, and produces more energy. This is what causes a star to expand.
When the star reaches the point where the fuel supply is exhausted, the star contracts, which increases the temperature in the core. This causes the star to fuse helium even faster, and the star continues to expand.
This process continues for millions or billions of years, causing the star to increase in size.
Eventually, the star becomes a supergiant.
Supergiant stars are red giants, because they have already lost most of their mass.
These stars will eventually explode as a supernova, producing a very bright, short-lived burst of light.
Simply put, when a main-sequence star exhausts its core hydrogen fuel supply, the star’s outer layers will expand and cool, eventually leading to the star’s death. Although the process is gradual, it is inevitable, and eventually all main-sequence stars will die. It is important to study these stars in order to better understand the universe in which we live.
