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| Photo by NASA on Unsplash |
[Working draft]
Stars have a limit on how big they can be, and when talking about big we are referring to different properties of a star. Some of a star properties are the diameter of the sphere, mass and density.
Depending on mass, a star can reach a point when it collapses on its on gravity. It is a this time when nuclear reactions, which releases energy, maintains the star from collapsing completely. The size of the star depends on the relationship between these two forces.
Where is the limit?
Very massive stars have such a density that their gravity ends up defeating the energy proceded by nuclear fusion, and collapse on their nucleus turning into neutron stars or black holes. We also have 'red giants', which are a kind of stars in their latest phase of their lives. Stars in this phase inflate and grow enormously, as an example when our sun finishes it current main sequence phase and turn into a red giant, we think it will expand enough to cover the orbit of the Earth and probably that of Mars. These red giants contain roughly the same mass as when they where in their main sequence but they are much bigger, so their density has decreased. Due to the big size the influence of gravity on the outer layers is small and as result great amount of material is thrown away forming a planetary nebula.
As big stars we have on one hand very massive stars, with such a high density that they end up collapsing, on the other hand stars with such a big radius that gravity cannot hold the outer layers of the star.
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| NASA, ESA and A. Feild (STScI) |
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