The Life Cycle of a Star

Universe Watch is looking at a double star called Gamma Delphini which is an interesting star as it is going through a process of becoming a giant star.


Gamma 2 Delphini

Gamma 2 Delphini ( Click to Enlarge)

In saying that, I thought it was probably a good time to mention here the  life cycle of a star.


Most stars that you can see in the sky are called Main Sequence stars or dwarf stars and the Sun is an example we will use here. Main Sequence stars are those where outward thermal pressure from nuclear fusion in the core is balanced by inward graviational pressure. So you could say that the star has achieved a stable and static equilibrium.

In about 6 billion years, our Sun will stop generating energy via hydrogen fusion, the same thing that is now happening to Gamma 2 Delphini. Our sun will then expand to become a Giant star. The bad news is that when that happens , it will take out the planets Mercury, Venus, Earth and possibly even Mars. So perhaps we should look at colonizing a planet other than Mars . But don’t worry…… 6 billion years is a long time to wait for this to happen.

The sun will eventually stabilize and shrink in size but not for long. When it runs out of energy, the core will eventually collapse until the sun becomes a white dwarf star, just the core, surrounded by remnants of what used to be it’s outer layer. In other words….. a planetary nebula.

When you hear about Giant stars, there are several types to consider. In this category you have the Hyper Giants, Super Giants and Bright Giants.

And the same goes for dwarfs where you have Subdwarfs, Red Dwarfs, White Dwarfs and Brown Dwarfs. Black Dwarfs are possible in the future but the Universe is not old enough yet for a Black Dwarf to exist yet. Black Dwarfs will begin to appear probably billion of years from now, again don’t bother waiting, when a White Dwarf stops producing heat and light.

~ by sydneystargazers on October 28, 2009.

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