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Current time: 27th June 2017, 02:54

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Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
#51
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
(18th January 2017, 16:57)Alex K Wrote:
(18th January 2017, 15:58)Rhondazvous Wrote: If there is too little co2, why doesn't adding more help?  And it's not just car emission but human and animal respiration adds to the co2 as well.
I think the point is if the current temperature were caused by large amounts of co2, we could pull that lever and cool by removing some of it. But since there's not that much there right now, you don'g get far trying to cool by removing co2. Imagine you are setting up a cupboard and realize it doesn't fit in your room bc the ceiling is too low. Then cutting off part of its legs would help, but if the legs are already short, you don't gain much. So you'd say the legs are too short to sufficiently shorten the cupboard.But of course making them longer wouldn't help but the opposite...

Let's try this again, Alex. He said there's too little co2, not too much. So you'd have to start with a cupboard that is too small for your room, and then show me how making the cupboard bigger wouldn't help. I'll be patient with you if you'll be patient with meSmile
Nietzsche isn't dead. How do I know he lives? He lives in my mind.
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#52
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
(18th January 2017, 17:52)Rhondazvous Wrote:
(18th January 2017, 16:57)Alex K Wrote: I think the point is if the current temperature were caused by large amounts of co2, we could pull that lever and cool by removing some of it. But since there's not that much there right now, you don'g get far trying to cool by removing co2. Imagine you are setting up a cupboard and realize it doesn't fit in your room bc the ceiling is too low. Then cutting off part of its legs would help, but if the legs are already short, you don't gain much. So you'd say the legs are too short to sufficiently shorten the cupboard.But of course making them longer wouldn't help but the opposite...

Let's try this again, Alex. He said there's too little co2, not too much. So you'd have to start with a cupboard that is too small for your room, and then show me how making the cupboard bigger wouldn't help. I'll be patient with you if you'll be patient with meSmile
Think of it this way:

The sun has been growing steadily warmer and brighter throughout earth's history.  But the earth has been able to keep its surface at roughly the same temperature during almost its entire history.  The way earth accomplished this was to steadily reduce the amount of CO2 and other greenhouse gases in its atmosphere.  It's like a person taking off layers of clothing as the room gets hotter to keep himself comfortable.

But the atmosphere is only about 0.04% CO2 now.  It's like the person is now down to underwear.   There is almost nothing more to take off,  but the sun is still getting hotter.   So soon the person would have to take off the underwear, and after that there is nothing more to take off.  After that, If the room continues to get hotter, as the sun will continue to do, he will overheat.

You can make the person put on some extra clothing just so he can take it off, that's like adding co2 to the atmosphere now.   but that doesn't help the heat situation because it just makes the person overheat right now, instead of some time after when he otherwise would have ran out of cloth to take off.
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#53
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
(18th January 2017, 19:18)Anomalocaris Wrote:
(18th January 2017, 17:52)Rhondazvous Wrote: Let's try this again, Alex. He said there's too little co2, not too much. So you'd have to start with a cupboard that is too small for your room, and then show me how making the cupboard bigger wouldn't help. I'll be patient with you if you'll be patient with meSmile
Think of it this way:

The sun has been growing steadily warmer and brighter throughout earth's history.  But the earth has been able to keep its surface at roughly the same temperature during almost its entire history.  The way earth accomplished this was to steadily reduce the amount of CO2 and other greenhouse gases in its atmosphere.  It's like a person taking off layers of clothing as the room gets hotter to keep himself comfortable.

But the atmosphere is only about 0.04% CO2 now.  It's like the person is now down to underwear.   There is almost nothing more to take off,  but the sun is still getting hotter.   So soon the person would have to take off the underwear, and after that there is nothing more to take off.  After that, If the room continues to get hotter, as the sun will continue to do, he will overheat.

You can make the person put on some extra clothing just so he can take it off, that's like adding co2 to the atmosphere now.   but that doesn't help the heat situation because it just makes the person overheat right now, instead of some time after when he otherwise would have ran out of cloth to take off.
Now I understand. So the planet is down to the last of the 7 veils.
Nietzsche isn't dead. How do I know he lives? He lives in my mind.
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#54
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
(16th January 2017, 08:35)Rhondazvous Wrote: What conditions cause a star to do one or the other?

Lots of factors I am sure, density and gravity I am sure play a huge role in either a slow expansion and peal off vs a collapse. But that is a great question.
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#55
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
Firstly, the most important factor that determines a stars evolution is it's mass. Our Sun is not even in the ball park mass to end in a supernova or a black hole. Stars spend their lives fusing hydrogen into heaver elements. Right now, The Sun is in a state of hydrostatic equilibrium. Nuclear fusion of Hydrogen into Helium causes an outward pressure via the energy produced in the reactions, which counterbalances the force of gravity. This energy via the proton-proton chain decreases the amount of matter at the Suns core slowly, causing the core to contract slightly and heat up. When the temperature rises the nuclear reactions become faster, which creates more pressure, where the Sun achieves a new equilibrium.

Eventually though, our Suns core will contract and the reactions will have to take place in a shell around the core. This will take the Sun off the main-sequence and grow into a red giant that will likely be larger than Earths orbit. The Sun will eject about 40% of it's mass and the out layers will produce what is called a planetary nebula similar to that of the Ring or Helix Nebula. All that will be left behind is but a white dwarf -- not a neutron star, which is a required first step to a black hole. Further, a neutron star must be a massive enough to overcome the electron degeneracy pressure, and further collapse to a black hole AKA the Chandrasekhar limit.



[Image: slide3.jpg]


A planetary nebula

[Image: ring-nebula.jpg?interpolation=lanczos-no...ize=*:1000]

More information . . .

http://www.atnf.csiro.au/outreach//educa...thlow.html

Quote:In an AGB star, if the helium fuel in the He-burning shell runs low, the outward radiation pressure drops off. As this was previously holding out the shell of hydrogen gas this shell now contracts, heats up and ignites, converting hydrogen to helium. This helium "ash" in turn falls onto the helium shell, heating it up till it is hot enough to re-ignite in a helium-shell flash, producing a thermal pulse. Increased radiation pressure now causes the hydrogen shell to expand and cool, shutting down H-shell burning.

The interval between successive thermal pulses decreases as the AGB star ages. For solar-mass stars such pulses dramatically increase the luminosity for several decades. Over time the outer layers of the AGB star are almost totally ejected and may initially appear as a circumstellar shell. The ejected cloud contains dust grains of silicates and graphite in addition to hydrogen and elements produced via nucleosynthesis reactions within the parent star. The cloud has typical expansion velocities of tens of kilometres per second.Our Sun will shed about 40% of its mass during this phase. More massive stars lose a greater percentage of their initial mass.

[Image: hrpostmainsuntrack.jpg]
Reply
#56
RE: Will Our Sun Expand and Go Nova or Shrink into a Black Hole?
Firstly, the most important factor that determines a stars evolution is it's mass. Our Sun is not even in the ball park mass to end in a supernova or a black hole. Stars spend their lives fusing hydrogen into heaver elements. Right now, The Sun is in a state of hydrostatic equilibrium. Nuclear fusion of Hydrogen into Helium causes an outward pressure via the energy produced in the reactions, which counterbalances the force of gravity. This energy via the proton-proton chain decreases the amount of matter at the Suns core slowly, causing the core to contract slightly and heat up. When the temperature rises the nuclear reactions become faster, which creates more pressure, where the Sun achieves a new equilibrium.

Eventually though, our Suns core will contract and the reactions will have to take place in a shell around the core. This will take the Sun off the main-sequence and grow into a red giant that will likely be larger than Earths orbit. The Sun will eject about 40% of it's mass and the out layers will produce what is called a planetary nebula similar to that of the Ring or Helix Nebula. All that will be left behind is but a white dwarf -- not a neutron star, which is a required first step to a black hole. Further, a neutron star must be a massive enough to overcome the electron degeneracy pressure, and further collapse to a black hole AKA the Chandrasekhar limit.

[Image: slide3.jpg]



A planetary nebula

[Image: ring-nebula.jpg?interpolation=lanczos-no...ize=*:1000]


More information . . .

http://www.atnf.csiro.au/outreach//educa...thlow.html

Quote:In an AGB star, if the helium fuel in the He-burning shell runs low, the outward radiation pressure drops off. As this was previously holding out the shell of hydrogen gas this shell now contracts, heats up and ignites, converting hydrogen to helium. This helium "ash" in turn falls onto the helium shell, heating it up till it is hot enough to re-ignite in a helium-shell flash, producing a thermal pulse. Increased radiation pressure now causes the hydrogen shell to expand and cool, shutting down H-shell burning.

The interval between successive thermal pulses decreases as the AGB star ages. For solar-mass stars such pulses dramatically increase the luminosity for several decades. Over time the outer layers of the AGB star are almost totally ejected and may initially appear as a circumstellar shell. The ejected cloud contains dust grains of silicates and graphite in addition to hydrogen and elements produced via nucleosynthesis reactions within the parent star. The cloud has typical expansion velocities of tens of kilometres per second.Our Sun will shed about 40% of its mass during this phase. More massive stars lose a greater percentage of their initial mass.


[Image: hrpostmainsuntrack.jpg]

(17th January 2017, 17:49)Stimbo Wrote:
(17th January 2017, 15:25)dyresand Wrote: Our sun doesn't contain enough mass to become a black hole but it will expand and go super nova in the end though.

It can't possibly. The Chandrasekhar Limit is 1.4 solar masses. Our Sun is 1 solar mass, by direct classification.

Exactly.
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