# What happens as a ball of iron gets larger?
**URL:** https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642
**Category:** Factual Questions
**Created:** [December 20, 2012, 5:25pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642 "2012-12-20T17:25:52Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@sweeteviljesus](https://boards.straightdope.com/u/sweeteviljesus)
#### Post date: [December 20, 2012, 5:25pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642/1 "2012-12-20T17:25:52Z")
If you had a ball of iron whose size you could increase (that is, add more iron to it) without bound, what would happen as the size increased? How large would it get before it underwent gravitational collapse? Five solar masses? How would the diameter change as the mass increased? Assume [sup]56[/sup]Fe.
Thanks,
Rob
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### Author:  [@Xema](https://boards.straightdope.com/u/Xema)
#### Post date: [December 20, 2012, 7:13pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642/2 "2012-12-20T19:13:09Z")
> [@](#):
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> How large would it get before it underwent gravitational collapse?
This sounds like the [Chandrasekhar limit](http://en.wikipedia.org/wiki/Chandrasekhar_limit) (1.44 solar masses) - the mass at which electron degeneracy pressure is no longer able to offset gravity.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [December 21, 2012, 5:33pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642/3 "2012-12-21T17:33:06Z")
There are a couple of different Chandrasekhar-like limits, one for the maximum mass of a white dwarf before it collapses into a neutron star, and one for the maximum mass of a neutron star before it collapses into a black hole (there might also be another step between neutron star and black hole for a quark star, but that’s a fairly narrow window). Neither one, though, addresses the question of when the lump of iron would collapse into a white dwarf-like object-- For that, you’d need information on the structural strength of iron under extreme conditions.
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### Author:  [@drewtwo99](https://boards.straightdope.com/u/drewtwo99)
#### Post date: [December 21, 2012, 5:41pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642/4 "2012-12-21T17:41:08Z")
Is iron special in some regard? Would the answer be vastly different if we used carbon or uranium instead? I suspect it has to do with the fact that iron is in that sweet point… I don’t know what to call it… between gains/losses of fission/fusion… but is that relevant to an ever increasing mass of iron?
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### Author:  [@sweeteviljesus](https://boards.straightdope.com/u/sweeteviljesus)
#### Post date: [December 21, 2012, 6:24pm UTC](https://boards.straightdope.com/t/what-happens-as-a-ball-of-iron-gets-larger/644642/5 "2012-12-21T18:24:32Z")
It’s my understanding that a large mass of iron won’t undergo gravity-induced fusion.
Rob