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Star live questions

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willpittenger

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I know the life sequence for a main sequence star like our Sun. I know how big stars end with a big bang. However, do really large stars and really small stars (red dwarfs) have the same types of layers? Would either swell or go through a similar color change during the life span? (I was thinking more relative to the average color put out throughout the star's life. A red dwarf would presumably only put out reds, but those reds would change.) Also would a red dwarf die like a main sequence star by sloughing off its outer layers? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>
 
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newtonian

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Will - Hi!<br /><br />Well, a red dwarf never gets hot enough to sustain nuclear reactions - so it would never slough off outer layers.<br /><br />My question is: could a red dwarf accrete hydrogen by passage though a hydrogen gas cloud and become a true star perhaps billions of years later?
 
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yevaud

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Actually, a Red Dwarf does indeed have Nuclear reactions, although just barely. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
 
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newtonian

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Yevaud - Actually, earth also has nuclear reactions. I meant nuclear fusion - and I misread a source which was talking about brown and red dwarfs and was referring to brown dwarfs not having nuclear reactions - likely meaning nuclear fusion.<br /><br />Do you have a good link on red dwarfs?
 
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yevaud

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UMD Document on Red Dwarf Stars<br /><br />It's fairly topical, but useful. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>
 
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nexium

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Newtonian is thinking of a brown dwarf which could become a true star by passing throuh a hydrogern cloud except hydrogen clouds thick enough and big enough are likely extremely rare. If the protostar just barely did not achieve fusion of hydrogen, the window of opportunity might be missed and adding several Jupiter masses of hygrogen would likely not start fusion at a later date. Most of the red dwarfs = class m, which formed 13 billion years ago are still on main sequence as they fuse hydrogen at a very low rate. The ones that are almost class k, have been observed to slough off much as class g stars. Our sun is class g2. Neil
 
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newtonian

Guest
Excellent. Thank you.<br /><br />Since a red dwarf can be up to .4 solar masses and has total mixing from core to surface, this gives me encouragement for my model for a 10 billion year stirring time for our sun for mixing from core to surface - caused by ions in motion and magnetic fields in motion, btw. I know that is not the standard model, btw.
 
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newtonian

Guest
Neil - What would happen to a red dwarf if it entered a stellar nursery and remained for a long time?
 
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thalion

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<i>I know how big stars end with a big bang. However, do really large stars and really small stars (red dwarfs) have the same types of layers?</i><br /><br />Stars more massive than ~0.4-5 solar masses are separated into a convective and radiative zone, so with increasingly larger main-sequence stars, there probably wouldn't be much of a difference in their inner layering. The only thing worth mentioning is that the radiative and convective zones in stars of more than a few solar masses are "reversed" relative the Sun; that is, their convective zone is in their core, and their radiative zone extends to the surface.<br /><br /><i>Would either swell or go through a similar color change during the life span? (I was thinking more relative to the average color put out throughout the star's life. A red dwarf would presumably only put out reds, but those reds would change.)</i> <br /><br />For most stars excluding red dwarfs, they would indeed go through stages similar to the Sun's, albeit at vastly different luminosities. However, the most massive stars--the "hypergiants"--will probably not get far enough to ever become orange or red supergiants, and will most likely explode before evolving that far; I'm thinking of Wolf-Rayet stars in particular.<br /><br />Believe it or not, red dwarfs will have a unique evolution from every other star type. As mentioned earlier, stars below a certain mass are fully convective. That means that their cores have access to all the hydrogen in their mass; given their low fusion rate, they have extremely long lifetimes.<br /><br />Non-red dwarf stars go through a giant and supergiant phase because they *don't* have access to all their hydrogen fuel; it's all a matter of the core trying to find new ways to acheive hydrostatic equilibrium. Hence, fully-convective red dwarfs will never become red giants or planetary nebulae; they will simply become hotter and smaller with time as they use up their hydrogen, until they become white dwarfs.
 
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abhinavkumar_iitr05

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Hello Newtonian,<br /><br />While going through the post I found u interested in the red dwarf.So here I m posting other link & if u r interested u can go through the link.<br /><br /> Red dwarf
 
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