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We’re Not the Only Living Ones in the Universe, Kind Of

The various stages of nuclear fusion in a high-mass star

For ages, humans have been questioning the possibility of other life forms in the universe. There are many theories and ideas of evidence of other life forms. For example, there appears to be dry river beds on Mars. It is thought that Mars could at one point retain water on its surface and life could’ve been sustained. There are other similar theories but what many tend to overlook are the seemingly infinite life forms that “twinkle” in our night sky: stars. We may not look like stars but there are similarities. Like humans, stars are born except they’re born out of gas clouds from older stars. Like humans, stars develop and change as they get older as they get more food (energy). Like humans, stars eventually get old and can no longer sustain life. The main difference, and perhaps most important aspect about a star, is the process that it undergoes to remain alive: nuclear fusion. Nuclear fusion is the process of fusing atoms of an element together which gives off energy.

The type of life a star will live, and its nuclear fusion process is determined once the star is born based on its birthweight, or how massive the star is when it starts fusing. If the birthweight is less than 2M, or two solar masses (two times the mass of our Sun), then the star is what we call a low-mass star. The nuclear fusion these stars undergo start out with fusing hydrogen to create helium. Once all of the hydrogen fuel is burned, the star will collapse and then expand to start fusing helium. After all of the helium fuel is fused to create carbon, the core is now primarily carbon but there isn’t enough gravitational energy to start fusing carbon and the core collapses. The outer portions, everything except the core, is blown away in a planetary nebula while the remaining core is left exposed as a white dwarf star.

Any star with a birthweight above 2M will typically have a longer life as a high-mass star. These stars follow the same process of low-mass stars except they continue fusing past carbon. In fact, they fuse each element all the way up to iron. Just like carbon was a low-mass star’s limit, iron is the end of the nuclear fusion process for high-mass stars. Iron can’t fuse into anything because the fusion will not create energy like each preceding fusion did. So, what happens? A supernova! Gravity collapses the core and the temperature rises to billions of Kelvin and then the rest of the star collapse and bounces off the neutron core. The result is a supernova nebula that actually creates the rest of the elements due to the extreme temperatures and abundance of energy.

So stars may not live like humans, but they have life cycles that we can link to our lives in different ways. They are born, they live, they die, and they give birth to other stars and elements. While they aren’t aliens that many want to find, stars are another form of life in our universe that we should no longer overlook as such.

2 thoughts on “We’re Not the Only Living Ones in the Universe, Kind Of

  1. TA Response:

    Very interesting post! It really provokes thought about what it means to be “living” thing, which is not always an easy definition to pin down.

    I am actually curious if referring to stars as living things would noticeably increase public interest in them.


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