# Where did iron come from? **URL:** \ **Category:** Factual Questions\ **Created:** [December 1, 2000, 3:38am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511 "2000-12-01T03:38:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Lightkeeper](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lightkeeper](https://boards.straightdope.com/u/Lightkeeper)\ **Post date:** [December 1, 2000, 3:38am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/1 "2000-12-01T03:38:24Z")
Here a question that puzzled me for a while! Where exactly did all the iron on earth come from? And how come there’s so much of it? I tried to look this up in book, libraries, even over the net but got nowhere. I read/heard somewhere that eventhough the sun contains iron, the metal was NOT produced in the sun (through nuclear fusion) because the core of the sun is not hot enough. So, what figures? Is it possible that it had extraterrestial origins? [WebElements.com](http://WebElements.com) says, “Iron is found native in meteorites known as siderites”… ---
**Author:** ![LifeWillFall](https://avatars.discourse-cdn.com/v4/letter/l/46a35a/32.png) [@LifeWillFall](https://boards.straightdope.com/u/LifeWillFall)\ **Post date:** [December 1, 2000, 3:42am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/2 "2000-12-01T03:42:36Z")
If I remember correctly Iron will not be created as a product of fusion because the bond structure will absorb energy and not produce it. I think iron is the lowest element for this to take place on, I know it doesn’t answer the question, but it’s kinda interesting none the less ---
**Author:** ![JasonFin](https://avatars.discourse-cdn.com/v4/letter/j/4af34b/32.png) [@JasonFin](https://boards.straightdope.com/u/JasonFin)\ **Post date:** [December 1, 2000, 4:02am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/3 "2000-12-01T04:02:22Z")
LifeWillFall, that is, in fact, the reason why Iron is the _heaviest_ element ever produced in stars under normal conditions. The fusion of elements into iron does release energy, though very little, so it will occur spontaneously (in the chemical sense) once a star runs low on other fusionable fuel, very late in its life cycle. Our sun is far from the stage when it will begin producing iron. (In fact, it may never enter such a stage. Can someone more familiar than I with steller-life cycles provide more detail? Because the fusion of iron requires energy, it will not occur spontaneously. Elements heavier than iron, which capture rather than release energy in their production, can be produced only in a supernova explosion. At such a time, energy is so abundant that heavy elements requiring a comparatively immense energy investment will form. Iron is abundant on Earth and other planets and planetoids largely because it is completely stable and quite common for an element so heavy. Sorry that I can’t provide more details. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 1, 2000, 4:05am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/4 "2000-12-01T04:05:23Z")
Sit down, Lightkeeper, I guess it’s time we had a little talk. You see, when the Mommy Iron and the Daddy Iron love each other they can hug in a special kind of way … ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [December 1, 2000, 4:06am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/5 "2000-12-01T04:06:05Z")
Actually, Iron is the one elment which cannot undergo fusion, and is therefore the final result of the near infinite pressure and heat of the largest of the stars. In fact, as soon as the core of a star becomes iron, it collapses into itself and goes supernova. Because all elements in the universe larger than carbon come from supernovae… you have a lot of iron. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [December 1, 2000, 4:06am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/6 "2000-12-01T04:06:32Z")
It is indeed extraterrestrial in origin. Good thing, or it never would have been around when the earth was forming… Most iron, IIRC, is made in supernovae. As has been pointed out, it’s the end product of nuclear reactions. In the last gasp of a star’s life, it’s creating iron. ---
**Author:** ![peace](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@peace](https://boards.straightdope.com/u/peace)\ **Post date:** [December 1, 2000, 4:10am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/7 "2000-12-01T04:10:09Z")
Why this preoccupation with iron? What about other 91 elements of the periodic table? And even if only iron were made on the sun 24/7, how would it get here? We get nothing but light and other rays from the sun. ---
**Author:** ![Lightkeeper](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lightkeeper](https://boards.straightdope.com/u/Lightkeeper)\ **Post date:** [December 1, 2000, 5:24am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/8 "2000-12-01T05:24:50Z")
Thanks for the replies, everone. I actually go the first reply seconds after posting! _ **JasonFin, Alessan, Smeghead:** _ Thanks for your feedback. Given all the info, I guess we can safely assume that all (or most) iron on Earth came from extraterrestial origin? I could be wrong, but the picture I can put together is this: Iron is only produced in supernovae explosions. Those explosions would send out asteroids with high percentages of iron (and heavier metals) into space. Lucky Earth got bombarded by lots of those asteroids sometime during its formation (must be LOTS coz 1/3 of the Earth’s mass is iron). This bombardment must have played an important role in the formation of Earth as we know it. I guess Earth would have looked very different without it. Regarding supernovae explosions, I had another question. When does a dying star explode (go supernova), and when does it implode (go black hole)? And what will our sun do? _ **Peace:** _ > [@](#): > > Why this preoccupation with iron? Good question. Well, it’s a constituent of haemoglobin and cholorophyll, so without it you don’t have plant or animal life. Besides, we first knew of magnetism (and, it follows, electricity, electronics, etc.) through the properties of iron… > [@](#): > > And even if only iron were made on the sun 24/7, how would it get here? We get nothing but light and other rays from the sun. Ummm… I guess we know that the Earth itself was seperated from the Sun (or do we?) That given, we can safely assume that much of the mass of the Earth came from the Sun. So, if the sun doesn’t produce iron, where did the iron in the earth come from? That was my question. _ **Little Nemo:** _ > [@](#): > > You see, when the Mommy Iron and the Daddy Iron love each other they can hug in a special kind of way … Go on, I’m listening! 😉 ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [December 1, 2000, 5:45am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/9 "2000-12-01T05:45:40Z")
Weeeel, sorta. Iron from supernovae would go out and become part of the interstellar clouds. The explosions wouldn’t send out asteroids, just gas. The earth, sun, and the rest of the solar system condensed out of one of those clouds - the iron here was created at least one star generation ago. So the earth had plenty of iron even before any bombarding began. As for whether a star goes supernova or black hole, it depends on its size. Above a certain limit, it becomes a black hole. Otherwise, it goes supernova. Or the other way around. I can’t remember, and I don’t have my notes from the last astronomy class I took (several years ago) handy. ---
**Author:** ![peace](https://avatars.discourse-cdn.com/v4/letter/p/c68b51/32.png) [@peace](https://boards.straightdope.com/u/peace)\ **Post date:** [December 1, 2000, 5:46am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/10 "2000-12-01T05:46:52Z")
\*\*Q: we know that the Earth itself was seperated from the Sun (or do we?)I don’t. Actually, that’s the first time I hear about it. Where do you live? I ain’t heard of iron in chlorophyll and not sure that ALL plants contain it, not ALL animal life contains hemoglobin; the amounts are tiny compared with mineral ore, anyway. Carbon plays more important role in organic life, even oxygen or nitrogen… ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [December 1, 2000, 5:50am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/11 "2000-12-01T05:50:11Z")
Lightkeeper, _Earth_ is of extraterrestrial origin. These supernovae happened Billions of years ago; the debris formed huge, swirling disks, which lated formed into stars and planets. This entire planet is made of the stuff of dead suns. ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [December 1, 2000, 5:50am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/12 "2000-12-01T05:50:30Z")
IIRC, a star at the end of its life goes supernova when it has a mass of something like 10 times the sun’s mass (?), and a star implodes into a black holes if its mass is more than 15 times solar mass (?). I’m not 100% sure of those numbers, but someone will be along to correct me shortly if I’m wrong 😃 Our sun will swell up into a red giant, remain that way for a while (a billion years or so, maybe?), then collapse into either a white dwarf or a brown dwarf… Sorry, don’t have my physics books here with me, or I’d give you more accurate numbers… ---
**Author:** ![Short](https://avatars.discourse-cdn.com/v4/letter/s/b38774/32.png) [@Short](https://boards.straightdope.com/u/Short)\ **Post date:** [December 1, 2000, 5:53am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/13 "2000-12-01T05:53:06Z")
> [@](#): > > \*Originally posted by Lightkeeper \* > **Well, it’s a constituent of haemoglobin…** And as I recall cobalt is also found in vitamin B12. Useless fact: yes Found on a bar napkin: no. ---
**Author:** ![Lightkeeper](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lightkeeper](https://boards.straightdope.com/u/Lightkeeper)\ **Post date:** [December 1, 2000, 7:37am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/14 "2000-12-01T07:37:01Z")
Thanks for the clarification, everyone! (I guess astronomy isn’t my forte!) > [@](#): > > \*Originally posted by Astroboy14 \* > \*\*IIRC, a star at the end of its life goes supernova when it has a mass of something like 10 times the sun’s mass (?), and a star implodes into a black holes if its mass is more than 15 times solar mass (?). I’m not 100% sure of those numbers, but someone will be along to correct me shortly if I’m wrong 😃 \*\* I checked it out via [Britannica.com](http://Britannica.com), it says: “only the most massive stars–those of more than three solar masses–become black holes at the end of their lives”. Thanks! ---
**Author:** ![Lightkeeper](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lightkeeper](https://boards.straightdope.com/u/Lightkeeper)\ **Post date:** [December 1, 2000, 7:42am UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/15 "2000-12-01T07:42:26Z")
> [@](#): > > \*Originally posted by peace \* > **Q: we know that the Earth itself was seperated from the Sun (or do we?)I don’t. Actually, that’s the first time I hear about it.** Yeah, I thought I could be wrong. > [@](#): > > \*\*Where do you live? \*\* Uh… actually I’m not from around here. I’m an alien. 😉 ---
**Author:** ![Ura-Maru](https://avatars.discourse-cdn.com/v4/letter/u/51bf81/32.png) [@Ura-Maru](https://boards.straightdope.com/u/Ura-Maru)\ **Post date:** [December 1, 2000, 12:08pm UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/16 "2000-12-01T12:08:40Z")
Heathens. Everyone knows that Iorn is the gift of **Crom.** – “Crom helps those who help themselves.” ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [December 1, 2000, 12:57pm UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/17 "2000-12-01T12:57:42Z")
Hi **Lightkeeper**!! And welcome!!! Also from [Britannica.com](http://Britannica.com): > [@](#): > > Black holes are the evolutionary endpoints of stars at least 10 to 15 times as massive as the Sun. The difficulty here is exactly **when** we are measuring the mass of the star that eventually becomes (or does not) a black hole! If we are measuring the mass during the **normal life time** of the star, then stars that are 10 times (and up) the mass of the sun will become black holes. If we are measuring the mass **immediately before stellar implosion** , then we are talking a mass of less than 10! Maybe as low as 3 solar masses… As a star burns up the last of its H, it collapses (due to the lack of outward pressure from the radiation generated as a result of fusing H into He), the collapse proceeds until the point where there is sufficient internal pressure to begin fusing He into Li and by-products (??.. former physics major here… going on memory…), when this next stage of fusion begins there is renewed pressure, and the star rapidly swells up _poof!_. This stage of fusion is short-lived, leading quickly to a new stage of collapse. The rapid collapse leaves behind a shell of expanding gas (a sizeable portion of the total mass of the former star)… see pretty picture [Here](http://oposite.stsci.edu/pubinfo/pr/1998/39/index.html). The star collapses **even more** until there is sufficient pressure to begin a new round of fusion… the star swells, throwing off more gas… collapses again! This continues until: 1)if the mass of what is left is **less** than some critical mass (sorry, don’t recall what that number is), the star burns out… brown or white dwarf or 2) if the mass left is in the range of 3 solar masses, the final collapse leads to a _ **HUGE** _ explosion!! **Supernova!!!** Cool!!! Unless you live nearby… ☹ or 3) if the mass remaining is greater than 3 or so solar masses, it continues to collapse, and becomes a _Get it? It’s a **black hole** , you can’t see it!!_😃 Hope this helps!! ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [December 1, 2000, 1:00pm UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/18 "2000-12-01T13:00:01Z")
uh…that should read **immediately before _the final_ stellar implosion** … sorry! ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [December 1, 2000, 1:58pm UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/19 "2000-12-01T13:58:40Z")
As was pointed out, we are made of star dust. Stars fuse hydrogen to helium and then up to iron which can no longer be used as fuel for fusion. Supernovae send these elements out into space where they become part of nebulae that may form new stars. The supernova explosions are powerful enough to form elements heavier than iron. So, after a few generations of stars, the material that formed our solar system had enough elements like iron to form terrestrial planets and life, etc. > [@](#): > > \*Originally posted by Astroboy14 \* > \*\*Our sun will swell up into a red giant, remain that way for a while (a billion years or so, maybe?), then collapse into either a white dwarf or a brown dwarf… > \*\* Our sun will first expand and then collapse into a white dwarf. A brown dwarf is an object that is not quite a star (a “failed star”). [http://www.britannica.com/bcom/eb/article/6/0,5716,16946+1+16702,00.html?query=brown%20dwarf](http://www.britannica.com/bcom/eb/article/6/0,5716,16946+1+16702,00.html?query=brown%20dwarf) Larger stars will end as a supernova whose cores collapse into neutron stars. Even larger stars collapse into black holes. ---
**Author:** ![Astroboy14](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Astroboy14](https://boards.straightdope.com/u/Astroboy14)\ **Post date:** [December 1, 2000, 2:08pm UTC](https://boards.straightdope.com/t/where-did-iron-come-from/43511/20 "2000-12-01T14:08:35Z")
Thanks **Phobos**!! I’m, literally, about 12,000 miles from my science books (they are in my bro’s basement, in Maine… I’m in Korea!) So the sun will eventually become a white dwarf! Where does Snow White fit into the picture?