Why are stars in the main sequence considered "stable"?

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>>MMM<<
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In my textbook it states that stars in the main sequence are considered stable. I don't quite follow what they mean?!
Do they mean they have a very long life considered to other phases (such as red giant) or what? please help im confused :confused:
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natninja
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(Original post by >>MMM<<)
In my textbook it states that stars in the main sequence are considered stable. I don't quite follow what they mean?!
Do they mean they have a very long life considered to other phases (such as red giant) or what? please help im confused :confused:
essentially they are the least likely to randomly blow up as they are 'young to middle-aged' to draw an analogy to a biological life cycle.
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>>MMM<<
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(Original post by natninja)
essentially they are the least likely to randomly blow up as they are 'young to middle-aged' to draw an analogy to a biological life cycle.
they can blow up randomly?! I thought this only happens at supernova?:confused:
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natninja
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(Original post by >>MMM<<)
they can blow up randomly?! I thought this only happens at supernova?:confused:
well not quite... but it just means that they are the least likely to stop being stars. red giants can supernova and developing stars can just not get hot enough and cool down and die.
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Joinedup
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Well you're largely right. We see a lot of stars in the main sequence because they tend to spend most of their lifecycle there compared to the length of time a star can be a red giants or young star for example.

Stability is a relative term when applied to stars though, Everything's on it's way to being something else
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>>MMM<<
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(Original post by Joinedup)
Well you're largely right. We see a lot of stars in the main sequence because they tend to spend most of their lifecycle there compared to the length of time a star can be a red giants or young star for example.

Stability is a relative term when applied to stars though, Everything's on it's way to being something else
I didn't quite follow what you mean
So am I right stability ----------> relatively longer life ?
Thanks
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>>MMM<<
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(Original post by natninja)
well not quite... but it just means that they are the least likely to stop being stars. red giants can supernova and developing stars can just not get hot enough and cool down and die.
thanks
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mikeyd85
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(Original post by >>MMM<<)
I didn't quite follow what you mean
So am I right stability ----------> relatively longer life ?
Thanks
Not necessarily. You can have a star that would have a relatively short life span (in the grand scheme of things). The stability of the star though would mean that you could more reasonably predict when the star would die.
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paddyman4
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It probably means that main sequence stars are in (hydrostatic) equilibrium and cannot easily be moved from this. The equilibirum is stable because the star self-regulates - if the nuclear reactions go too fast, the star gets too hot, the star expands, the star cools, the nuclear reactions calm down.

It's not really anything to do with the star 'not randomly blowing up' or not dying or anything.
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lilstotty97
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Stars are stable during the 'main sequance' period of the life cycle. Why?
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lilstotty97
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Stars are stable during the 'main sequance' period of the life cycle. Why? :confused:
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uberteknik
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(Original post by lilstotty97)
Stars are stable during the 'main sequance' period of the life cycle. Why? :confused:
Hello and welcome to TSR.

The forces acting on the star are in balance.

Gravitational attraction compresses the star so that in the core, nuclear fusion starts to convert hydrogen to helium.

This releases some of the nuclear binding energy (hydrogen nucleus) which creates an outward thermal pressure, thus counteracting further gravitational collapse. An equilibrium is achieved. The outward thermal forces are balanced with the inwards gravitational forces.

Depending on the original mass of the star, this stable period can last billions of years until all of the hydrogen in the star is converted to helium.

(PS. For future posts, you might like to check the date of the last post, which is in the top right hand corner of the grey banner. Posting a new question on the Physics section of the Study Forum is a safer way to get a quick answer. )
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