Iron Is the End of the Line for a Star
Iron is a common metallic element. Stars can fuse elements up to iron and no further.
Iron is a hard grey metallic element, the commonest on Earth by mass. It marks a hard limit in physics: fusing lighter elements releases energy, but fusing iron consumes it, so a massive star building an iron core has no fuel left and collapses. Everything heavier than iron was forged in that collapse or in colliding neutron stars. The symbol Fe comes from Latin *ferrum*, and the word *iron* itself is Germanic, unrelated to the Latin.
- A metallic element. *Cast iron.*
- A pressing appliance. *A steam iron.*
- A golf club. *A seven iron.*
- Ferrous — of iron. *Ferrous.*
- Old English — *iren*. *The source.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | iron | Iron. |
| Verb | iron | Ironing. |
| Adjective | ferrous | Ferrous. |
| Symbol | Fe | Fe. |
| Latin | ferrum | Iron. |
- The gate is wrought iron.Metal.
- She ironed the shirt.Verb.
- Fe comes from ferrum.Chemistry.
Why iron ends stellar fusion
- Fusing light elements releases energy and supports the star
- Iron has the most tightly bound nucleus of any element
- Fusing it absorbs energy instead of releasing it
- The core loses support and collapses
- Heavier elements form in that collapse and in neutron star collisions
Old English *iren*, of Germanic origin. The symbol Fe is from Latin *ferrum*, an unrelated word.
Why can stars not fuse past iron?
Iron has the most tightly bound nucleus, so fusing it absorbs energy rather than releasing it, and the core can no longer support itself.
Why is iron's symbol Fe?
From Latin ferrum. The English word iron is Germanic and unrelated to the Latin name.