Why is iron the end all for stars?

I am not a scientist or astronomer, so I saw a program on the science channel that stated that iron was the end all for stars. I understand the helium/hydrogen connection but I did not fully understand how iron of all things was the "kryptonite" for stars. Some smarter than me (there are many) please help explain. Thanks!

reply to post by swampcricket

I did not know either swampcricket. I found this link

Stars greater than 25 solar masses undergo a more violent end to their lives. Carbon core burning lasts for 600 years for a star of this size. Neon burning for 1 year, oxygen burning about 6 months (i.e. very fast on astronomical timescales). At 3 billion degrees, the core can fuse silicon nuclei into iron and the entire core supply is used up in one day.

An inert iron core builds up at this time where successive layers above the core consume the remaining fuel of lighter nuclei in the core. The core is about the size of the Earth, compressed to extreme densities and near the Chandrasekhar limit. The outer regions of the star have expanded to fill a volume as large as Jupiter's orbit from the Sun. Since iron does not act as a fuel, the burning stops.

The sudden stoppage of energy generation causes the core to collapse and the outer layers of the star to fall onto the core. The infalling layers collapse so fast that they `bounce' off the iron core at close to the speed of light. The rebound causes the star to explode as a supernova.

Hope that helps and hey we both learned something new today.

reply to post by swampcricket


Iron is the lowest energy state for matter. You can’t get any more energy out of it once it has fused to iron. If anything atomically happens to iron, then it takes energy, instead of gives energy. That is to say, iron is at the bottom of the energy totem pole. All material slowly works it way to that state (to the bottom). So, iron is basically an inert material inside of a star and just fills space while giving nothing to the energy production. Once the percentage of inert material gets so high, then the star’s energy reaction can’t continue.

makes one think about iron meteorites

dead suns from years ago, floating through space

thanks for this

peace

Light elements undergoing nuclear fusion release energy as their nucleons bind more tightly. In iron atoms, the nuclei are bound extremely tightely, and fusion would consume more energy than it releases. en.wikipedia.org...

Originally posted by swampcricket
I am not a scientist or astronomer, so I saw a program on the science channel that stated that iron was the end all for stars. I understand the helium/hydrogen connection but I did not fully understand how iron of all things was the "kryptonite" for stars. Some smarter than me (there are many) please help explain. Thanks!

The excerpts 'speculativeoptimist' provided above is a good explanation as to why the production of a iron core is a good symptom that a star is about to nova or supernova...

...but there is another interesting connection between stars and iron (and all other heavy elements):

All elements heavier than hydrogen, lithium, and beryllium were created inside stars. As the theory goes, the Big Bang only created those three lightest elements. It took the heat and pressure of stars to (basically) squeeze those lighter elements together to form the heavier ones.

The first generation of stars in the early universe fused atoms together in order to form some of the medium-heavy elements, such as oxygen and carbon. The carbon in your body and the oxygen you are breathing were made inside of stars.

Those first generation stars died off, and the stuff inside of them became second generation stars. Those stars and the dust and/or planets that surrounded them contained these medium-heavy elements. Then, in the pressure and heat created when those second-generation stars went nova or supernova, those elements fused together to form the heaviest elements -- iron, gold, zinc, etc -- which were scattered through space in the nova explosion.

Those heaviest elements then wound up in clouds of dust and gas that, about 5 billion years ago, again formed into another solar system with a sun and planets -- our solar system.

So not only the oxygen you breathe and the carbon in your cells, but also the iron in your blood and the gold in your jewelry, all of those atoms were created in a supernova of a star billions of years ago.

Carl Sagan once famously said "We are made of star-stuff", and he meant it quite literally, because we literally are.

reply to post by Soylent Green Is People

Some of those early generation stars may still exist:
ca.news.yahoo.com - Oldest star in the universe is right in our stellar neighborhood...

What gets me confused is it's strange to acknowledge that our solar system is several billion years old and then also acknowledge that OUR UNIVERSE is only about 13.7 billion years old.

Also this:
www.geekosystem.com - The End Is Nigh Billions of Years Away: Higgs Discovery Might Suggest Universe is Finite...

........
The specific numbers of when the Universe could end are still being pinned down, but it’s billions of years away, so it doesn’t much matter. Especially when you consider that the Sun will burn out and engulf the Earth in about 4.5 billion years and there’s nothing we can do about it because we’ll all be long dead by then.
..........

Everyone talking about the dead state of Iron makes me wonder......How could we get to our most energetic and powerful state by consuming food high in iron. The same thing with calcium, calcium buffers energy production in the body which is opposite of what they are telling us.. Sorry for getting off topic, but from what I have been reading, it seems to open up my mind to possibilities of something unrelated.

reply to post by rickymouse


We evolved to use iron atoms in our bodies simply as a vehicle to transport oxygen around in our bloodstreams. A nice example of making good use of what's readily available in an efficient manner. Calcium is a building block for our structural framework of bones and teeth etc.

There have been some good answers already.
I'll take a stab.
Atoms fuse together inside stars in a process known as fusion. It takes tremendous heat and or pressure to achieve this. Stars have enough mass for the process to start. Jupiter for example does not. If you had 75 Jupiters, then it might start.

All this tremendous mass pushes in towards the center of the mass. Fusion takes place. During the fusion process, two hydrogen atoms fuse together to form a heavier element. Tremendous energy is released. More energy is released than it took to fuse the atoms together. This energy release pushes all the incoming mass of a star back out. All the lighter atoms of a star work as fuel until they convert into heavier elements. This process goes on until the energy released from fusion no longer exceeds the pressure from all the mass pressing into a star. At that point, you might get a super massive explosion. I forgot all the details of the process.

Anyway in a supernova, heavier elements undergo fusion. Gold, platinum, silver, etc all were created in a supernova explosion that ended up in our solar system. The element of iron is the point of no return. It takes more energy to fuse heavier elements after iron then you get out of the fusion process.

As a little side note, if your body was inside a star, the atoms in your body might experience enough pressure to undergo the fusion process. Here on Earth, the food in your stomach is not under much pressure. Maybe if you had 75 Jupiters on top of your stomach your atoms might undergo fusion. If your atoms did have a fusion reaction, you'd probably light up your entire city. I don't think you'll get that much energy from whatever you eat.

Originally posted by rickymouse
Everyone talking about the dead state of Iron makes me wonder......How could we get to our most energetic and powerful state by consuming food high in iron. The same thing with calcium, calcium buffers energy production in the body which is opposite of what they are telling us.. Sorry for getting off topic, but from what I have been reading, it seems to open up my mind to possibilities of something unrelated.

Iron is stable, not dead. Chemistry (including biological use of iron) has more to do with electrons rather than nucleons. Oxygen is electrong-hungry, and iron atom has a lot of electrons to offer (hence its good conductivity), therefore iron is good at binding oxygen. It's the oxygen that gives us energy, not iron.

The electron configuration of calcium makes it advantageous for it to give up two electrons, again allowing for chemical reactions.

Thanks for all of the replies and info, it makes sense now!

Originally posted by swampcricket
I am not a scientist or astronomer, so I saw a program on the science channel that stated that iron was the end all for stars.

Iron isn't the end for all stars. It's the last product of fusion but only in more massive stars. Some smaller stars don't have enough mass to produce iron from fusion. They end (run out of fuel) without ever producing iron.

The end for the large stars is a supernova, and it is the supernova that produces elements heavier than iron (like uranium, for example). So in this case, iron isn't really the end, it is just the last fusion product immediately prior to the real end, the supernova.

Originally posted by speculativeoptimist
reply to post by swampcricket

 

I did not know either swampcricket. I found this link

Stars greater than 25 solar masses undergo a more violent end to their lives. Carbon core burning lasts for 600 years for a star of this size. Neon burning for 1 year, oxygen burning about 6 months (i.e. very fast on astronomical timescales). At 3 billion degrees, the core can fuse silicon nuclei into iron and the entire core supply is used up in one day.

An inert iron core builds up at this time where successive layers above the core consume the remaining fuel of lighter nuclei in the core. The core is about the size of the Earth, compressed to extreme densities and near the Chandrasekhar limit. The outer regions of the star have expanded to fill a volume as large as Jupiter's orbit from the Sun. Since iron does not act as a fuel, the burning stops.

The sudden stoppage of energy generation causes the core to collapse and the outer layers of the star to fall onto the core. The infalling layers collapse so fast that they `bounce' off the iron core at close to the speed of light. The rebound causes the star to explode as a supernova.

Hope that helps and hey we both learned something new today.

This is a theory, which I am sure will change as science evolves.

There is no doubt that nuclear fusion as well as nuclear fission goes on inside stars and even planets.

However there is no "definitive" explanation yet offered by modern science.

reply to post by GargIndia

Again, one of those "it's just a theory, science doesn't have a real answer" replies. What is the point of such a reply? Everything in science is a theory. Science is always learning. Some theories change pretty fast, some are more stable. The gravitational collapse theory is pretty solid, I don't see it changing any time soon. If you think about it, given the titanic mass of stars, nuclear fusion is the only reason they don't collapse, and when fusion does stop and they do collapse, the results are catastrophic (supernova, black hole or a neutron star). Do you really have a valid reason to doubt that theory?

/rant

reply to post by wildespace


Do I have reasons to doubt this theory?

Yes.

Do I have an alternate theory?

Yes.

I shall offer only one reason for now. The theory is based on mathematical models and heavenly observations. The fundamental law of science - direct observation, is missing. As humans do not have the capability to go into deep space and observe the phenomenon with greater clarity.

This forum is not the right place to discuss such serious topics as origins of Universe and the creation/destruction of stars. So I shall stop right here.

Originally posted by rickymouse
Everyone talking about the dead state of Iron makes me wonder......How could we get to our most energetic and powerful state by consuming food high in iron. The same thing with calcium, calcium buffers energy production in the body which is opposite of what they are telling us.. Sorry for getting off topic, but from what I have been reading, it seems to open up my mind to possibilities of something unrelated.

I believe the answer is in the question, non life fuels life. The sun, various minerals, compounds, liquids and gasses.

We may not understand the role life plays in the universe just yet, but we are likely here to balance it's existence.

Originally posted by GargIndia
reply to post by wildespace

 

Do I have reasons to doubt this theory?

Yes.

Do I have an alternate theory?

Yes.

I shall offer only one reason for now. The theory is based on mathematical models and heavenly observations. The fundamental law of science - direct observation, is missing. As humans do not have the capability to go into deep space and observe the phenomenon with greater clarity.

This forum is not the right place to discuss such serious topics as origins of Universe and the creation/destruction of stars. So I shall stop right here.

And please tell us why the Space Exploration forum is not the right place to discuss topics such as the origins of the universe and the birth and death of stars?

What forum here on ATS do you feel that this subject should be better discussed at?

I need to ask 2 stupid questions
1 in 5 billion years or there about when our sun goes super nova, it will fuse our heavy elements into even heavier super elements that do not exist now. Any idea what they can be?
2 is it possible that that process might had happened somewhere else in our solar system.

Originally posted by jonnywhite
reply to post by Soylent Green Is People

 

Some of those early generation stars may still exist:
ca.news.yahoo.com - Oldest star in the universe is right in our stellar neighborhood...

What gets me confused is it's strange to acknowledge that our solar system is several billion years old and then also acknowledge that OUR UNIVERSE is only about 13.7 billion years old.

Also this:
www.geekosystem.com - The End Is Nigh Billions of Years Away: Higgs Discovery Might Suggest Universe is Finite...

........
The specific numbers of when the Universe could end are still being pinned down, but it’s billions of years away, so it doesn’t much matter. Especially when you consider that the Sun will burn out and engulf the Earth in about 4.5 billion years and there’s nothing we can do about it because we’ll all be long dead by then.
..........

edit on 9-8-2013 by jonnywhite because: (no reason given)

For our part of the galaxy, where the Sun and the nearest stars are now, there have been several super-massive red-giants. Each might have lasted just 3-4 billion years, before exploding and sending shockwaves through the early galactic dust clouds, causing new star formation. But each one generated more elements like carbon, oxygen and iron. During the super-nova explosion, all the heavier-than-iron elements like uranium and mercury are formed through neutron bombardment and other processes.

When you look at maps of the galaxy, the blue giant stars are some of the oldest areas of the galaxy.

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