# The life and death of a star

> A process map exported from forks.world (https://forks.world). Author: Brian. Source: https://forks.world/p/cmv0idz7h000jjw06rb65zt7m
> It describes who does what, in what order, and with which technology. Read the plain-language sections first; the JSON at the end is the exact, complete data.

## Summary

- 33 steps across 4 layers
- Persona: Gas cloud, Us, looking up
- Technology / systems: The star, The core

## How to read this file

- A process is made of **layers**. The main layer is the top level; any step of kind `subprocess` opens a detail layer with its own lanes and steps.
- **Lanes** are either persona (people/roles) or technology (systems). Each step belongs to one lane; `using` lists tools a person uses for that step.
- Step kinds: `start`, `task`, `decision` (its arrows carry the answer as a label), `subprocess`, `end`.

## The life and death of a star

Lanes:
- Gas cloud: person / role (id `cloud`)
- The star: technology / system (id `star`)
- The core: technology / system (id `core`)
- Us, looking up: person / role (id `obs`)

Steps, in the order they run:

1. **A giant cloud of hydrogen collapses under its own gravity** [start; Gas cloud; id `s1`]
   - then Core hot and dense enough to fuse hydrogen?
2. **Core hot and dense enough to fuse hydrogen?** [decision; The core; id `s2`]
   - if "Yes" go to Hydrogen fuses into helium: a star is born; if "No" go to It never ignites: a brown dwarf, a failed star
3. **Hydrogen fuses into helium: a star is born** [subprocess; The star; id `s3`], opens the detail layer "Staying balanced for billions of years"
   - then Billions of years of steady shining
4. **Billions of years of steady shining** [task; The star; id `s4`]
   - then Hydrogen in the core runs out
5. **Hydrogen in the core runs out** [task; The core; id `s5`]
   - then More than about 8 times the Sun's mass?
6. **More than about 8 times the Sun's mass?** [decision; The star; id `s6`]
   - if "Yes" go to Fuses heavier and heavier elements; if "No" go to Swells into a red giant
7. **Fuses heavier and heavier elements** [subprocess; The star; id `s7`], opens the detail layer "Burning heavier and heavier"
   - then Iron can't release energy: the core collapses
8. **Iron can't release energy: the core collapses** [task; The core; id `s9`]
   - then The core rebounds in a supernova
9. **The core rebounds in a supernova** [subprocess; The star; id `s10`], opens the detail layer "Supernova"
   - then What's left depends on the core's mass
10. **What's left depends on the core's mass** [decision; The core; id `s11`]
   - if "Under about 3 suns" go to A neutron star: a city-sized ball of pure nuclear density; if "Over about 3 suns" go to A black hole: not even light escapes
11. **A neutron star: a city-sized ball of pure nuclear density** [task; The core; id `s12`]
   - then Stardust seeds new stars and planets. Including you.
12. **Stardust seeds new stars and planets. Including you.** [end; Us, looking up; id `s14`]
13. **A black hole: not even light escapes** [task; The core; id `s13`]
   - then Stardust seeds new stars and planets. Including you.
14. **Swells into a red giant** [task; The star; id `s8`]
   - then Sheds its outer layers as a glowing nebula
15. **Sheds its outer layers as a glowing nebula** [task; The star; id `s15`]
   - then The core cools into a white dwarf
16. **The core cools into a white dwarf** [task; The core; id `s16`]
   - then Stardust seeds new stars and planets. Including you.
17. **It never ignites: a brown dwarf, a failed star** [end; The core; id `s2a`]

```mermaid
flowchart LR
  subgraph l_cloud["Gas cloud"]
    n_s1(["A giant cloud of hydrogen collapses under its own gravity"])
  end
  subgraph l_star["The star"]
    n_s3[["Hydrogen fuses into helium: a star is born"]]
    n_s4["Billions of years of steady shining"]
    n_s6{"More than about 8 times the Sun's mass?"}
    n_s7[["Fuses heavier and heavier elements"]]
    n_s10[["The core rebounds in a supernova"]]
    n_s8["Swells into a red giant"]
    n_s15["Sheds its outer layers as a glowing nebula"]
  end
  subgraph l_core["The core"]
    n_s2{"Core hot and dense enough to fuse hydrogen?"}
    n_s2a(["It never ignites: a brown dwarf, a failed star"])
    n_s5["Hydrogen in the core runs out"]
    n_s9["Iron can't release energy: the core collapses"]
    n_s11{"What's left depends on the core's mass"}
    n_s12["A neutron star: a city-sized ball of pure nuclear density"]
    n_s13["A black hole: not even light escapes"]
    n_s16["The core cools into a white dwarf"]
  end
  subgraph l_obs["Us, looking up"]
    n_s14(["Stardust seeds new stars and planets. Including you."])
  end
  n_s1 --> n_s2
  n_s2 -->|"Yes"| n_s3
  n_s2 -->|"No"| n_s2a
  n_s3 --> n_s4
  n_s4 --> n_s5
  n_s5 --> n_s6
  n_s6 -->|"Yes"| n_s7
  n_s6 -->|"No"| n_s8
  n_s7 --> n_s9
  n_s9 --> n_s10
  n_s10 --> n_s11
  n_s11 -->|"Under about 3 suns"| n_s12
  n_s11 -->|"Over about 3 suns"| n_s13
  n_s12 --> n_s14
  n_s13 --> n_s14
  n_s8 --> n_s15
  n_s15 --> n_s16
  n_s16 --> n_s14
```

### Staying balanced for billions of years (detail of step "Hydrogen fuses into helium: a star is born")

Lanes:
- The star: technology / system (id `star`)
- The core: technology / system (id `core`)

Steps, in the order they run:

1. **Gravity pulls everything inward** [start; The star; id `m1`]
   - then Fusion heat pushes outward
2. **Fusion heat pushes outward** [task; The core; id `m2`]
   - then Pressure and gravity balanced?
3. **Pressure and gravity balanced?** [decision; The star; id `m3`]
   - if "Yes" go to Steady glow for billions of years; if "No" go to Star swells or shrinks until they balance
4. **Steady glow for billions of years** [end; The star; id `m4`]
5. **Star swells or shrinks until they balance** [task; The star; id `m5`]
   - then Pressure and gravity balanced?

```mermaid
flowchart LR
  subgraph l_star["The star"]
    n_m1(["Gravity pulls everything inward"])
    n_m3{"Pressure and gravity balanced?"}
    n_m5["Star swells or shrinks until they balance"]
    n_m4(["Steady glow for billions of years"])
  end
  subgraph l_core["The core"]
    n_m2["Fusion heat pushes outward"]
  end
  n_m1 --> n_m2
  n_m2 --> n_m3
  n_m3 -->|"Yes"| n_m4
  n_m3 -->|"No"| n_m5
  n_m5 --> n_m3
```

### Supernova (detail of step "The core rebounds in a supernova")

Lanes:
- The star: technology / system (id `star`)
- The core: technology / system (id `core`)
- Us, looking up: person / role (id `obs`)

Steps, in the order they run:

1. **The iron core collapses in under a second** [start; The core; id `n1`]
   - then Protons and electrons squeeze into neutrons
2. **Protons and electrons squeeze into neutrons** [task; The core; id `n2`]
   - then Outer layers crash onto the rigid core
3. **Outer layers crash onto the rigid core** [task; The star; id `n3`]
   - then Do they bounce back?
4. **Do they bounce back?** [decision; The star; id `n4`]
   - if "Yes" go to A shockwave blasts the star apart; if "No" go to A flood of neutrinos gives the shock a push
5. **A shockwave blasts the star apart** [task; The star; id `n5`]
   - then Outshines a whole galaxy for weeks
6. **Outshines a whole galaxy for weeks** [end; Us, looking up; id `n7`]
7. **A flood of neutrinos gives the shock a push** [task; The core; id `n6`]
   - then Do they bounce back?

```mermaid
flowchart LR
  subgraph l_star["The star"]
    n_n3["Outer layers crash onto the rigid core"]
    n_n4{"Do they bounce back?"}
    n_n5["A shockwave blasts the star apart"]
  end
  subgraph l_core["The core"]
    n_n1(["The iron core collapses in under a second"])
    n_n2["Protons and electrons squeeze into neutrons"]
    n_n6["A flood of neutrinos gives the shock a push"]
  end
  subgraph l_obs["Us, looking up"]
    n_n7(["Outshines a whole galaxy for weeks"])
  end
  n_n1 --> n_n2
  n_n2 --> n_n3
  n_n3 --> n_n4
  n_n4 -->|"Yes"| n_n5
  n_n4 -->|"No"| n_n6
  n_n6 --> n_n4
  n_n5 --> n_n7
```

### Burning heavier and heavier (detail of step "Fuses heavier and heavier elements")

Lanes:
- The core: technology / system (id `core`)

Steps, in the order they run:

1. **Helium fuses into carbon and oxygen** [start; The core; id `h1`]
   - then Then neon, oxygen and silicon burn in turn
2. **Then neon, oxygen and silicon burn in turn** [task; The core; id `h2`]
   - then Each stage lasts less time than the last
3. **Each stage lasts less time than the last** [task; The core; id `h3`]
   - then Silicon burns into iron in about a day
4. **Silicon burns into iron in about a day** [end; The core; id `h4`]

```mermaid
flowchart LR
  subgraph l_core["The core"]
    n_h1(["Helium fuses into carbon and oxygen"])
    n_h2["Then neon, oxygen and silicon burn in turn"]
    n_h3["Each stage lasts less time than the last"]
    n_h4(["Silicon burns into iron in about a day"])
  end
  n_h1 --> n_h2
  n_h2 --> n_h3
  n_h3 --> n_h4
```

## Full data (JSON)

```json
{
  "title": "The life and death of a star",
  "maps": {
    "m_main": {
      "id": "m_main",
      "lanes": [
        {
          "id": "star",
          "name": "The star",
          "type": "system"
        },
        {
          "id": "core",
          "name": "The core",
          "type": "system"
        }
      ],
      "steps": [
        {
          "id": "m1",
          "kind": "start",
          "lane": "star",
          "next": [
            {
              "to": "m2"
            }
          ],
          "uses": [],
          "label": "Gravity pulls everything inward"
        },
        {
          "id": "m2",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "m3"
            }
          ],
          "uses": [],
          "label": "Fusion heat pushes outward"
        },
        {
          "id": "m3",
          "kind": "decision",
          "lane": "star",
          "next": [
            {
              "to": "m4",
              "label": "Yes"
            },
            {
              "to": "m5",
              "label": "No"
            }
          ],
          "uses": [],
          "label": "Pressure and gravity balanced?"
        },
        {
          "id": "m5",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "m3"
            }
          ],
          "uses": [],
          "label": "Star swells or shrinks until they balance"
        },
        {
          "id": "m4",
          "kind": "end",
          "lane": "star",
          "next": [],
          "uses": [],
          "label": "Steady glow for billions of years"
        }
      ],
      "title": "Staying balanced for billions of years",
      "parent": {
        "map": "m_root",
        "step": "s3"
      }
    },
    "m_nova": {
      "id": "m_nova",
      "lanes": [
        {
          "id": "star",
          "name": "The star",
          "type": "system"
        },
        {
          "id": "core",
          "name": "The core",
          "type": "system"
        },
        {
          "id": "obs",
          "name": "Us, looking up",
          "type": "person"
        }
      ],
      "steps": [
        {
          "id": "n1",
          "kind": "start",
          "lane": "core",
          "next": [
            {
              "to": "n2"
            }
          ],
          "uses": [],
          "label": "The iron core collapses in under a second"
        },
        {
          "id": "n2",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "n3"
            }
          ],
          "uses": [],
          "label": "Protons and electrons squeeze into neutrons"
        },
        {
          "id": "n3",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "n4"
            }
          ],
          "uses": [],
          "label": "Outer layers crash onto the rigid core"
        },
        {
          "id": "n4",
          "kind": "decision",
          "lane": "star",
          "next": [
            {
              "to": "n5",
              "label": "Yes"
            },
            {
              "to": "n6",
              "label": "No"
            }
          ],
          "uses": [],
          "label": "Do they bounce back?"
        },
        {
          "id": "n6",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "n4"
            }
          ],
          "uses": [],
          "label": "A flood of neutrinos gives the shock a push"
        },
        {
          "id": "n5",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "n7"
            }
          ],
          "uses": [],
          "label": "A shockwave blasts the star apart"
        },
        {
          "id": "n7",
          "kind": "end",
          "lane": "obs",
          "next": [],
          "uses": [],
          "label": "Outshines a whole galaxy for weeks"
        }
      ],
      "title": "Supernova",
      "parent": {
        "map": "m_root",
        "step": "s10"
      }
    },
    "m_root": {
      "id": "m_root",
      "lanes": [
        {
          "id": "cloud",
          "name": "Gas cloud",
          "type": "person"
        },
        {
          "id": "star",
          "name": "The star",
          "type": "system"
        },
        {
          "id": "core",
          "name": "The core",
          "type": "system"
        },
        {
          "id": "obs",
          "name": "Us, looking up",
          "type": "person"
        }
      ],
      "steps": [
        {
          "id": "s1",
          "kind": "start",
          "lane": "cloud",
          "next": [
            {
              "to": "s2"
            }
          ],
          "uses": [],
          "label": "A giant cloud of hydrogen collapses under its own gravity"
        },
        {
          "id": "s2",
          "kind": "decision",
          "lane": "core",
          "next": [
            {
              "to": "s3",
              "label": "Yes"
            },
            {
              "to": "s2a",
              "label": "No"
            }
          ],
          "uses": [],
          "label": "Core hot and dense enough to fuse hydrogen?"
        },
        {
          "id": "s2a",
          "kind": "end",
          "lane": "core",
          "next": [],
          "uses": [],
          "label": "It never ignites: a brown dwarf, a failed star"
        },
        {
          "id": "s3",
          "kind": "subprocess",
          "lane": "star",
          "next": [
            {
              "to": "s4"
            }
          ],
          "uses": [],
          "child": "m_main",
          "label": "Hydrogen fuses into helium: a star is born"
        },
        {
          "id": "s4",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "s5"
            }
          ],
          "uses": [],
          "label": "Billions of years of steady shining"
        },
        {
          "id": "s5",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "s6"
            }
          ],
          "uses": [],
          "label": "Hydrogen in the core runs out"
        },
        {
          "id": "s6",
          "kind": "decision",
          "lane": "star",
          "next": [
            {
              "to": "s7",
              "label": "Yes"
            },
            {
              "to": "s8",
              "label": "No"
            }
          ],
          "uses": [],
          "label": "More than about 8 times the Sun's mass?"
        },
        {
          "id": "s7",
          "kind": "subprocess",
          "lane": "star",
          "next": [
            {
              "to": "s9"
            }
          ],
          "uses": [],
          "child": "m_heavy",
          "label": "Fuses heavier and heavier elements"
        },
        {
          "id": "s9",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "s10"
            }
          ],
          "uses": [],
          "label": "Iron can't release energy: the core collapses"
        },
        {
          "id": "s10",
          "kind": "subprocess",
          "lane": "star",
          "next": [
            {
              "to": "s11"
            }
          ],
          "uses": [],
          "child": "m_nova",
          "label": "The core rebounds in a supernova"
        },
        {
          "id": "s11",
          "kind": "decision",
          "lane": "core",
          "next": [
            {
              "to": "s12",
              "label": "Under about 3 suns"
            },
            {
              "to": "s13",
              "label": "Over about 3 suns"
            }
          ],
          "uses": [],
          "label": "What's left depends on the core's mass"
        },
        {
          "id": "s12",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "s14"
            }
          ],
          "uses": [],
          "label": "A neutron star: a city-sized ball of pure nuclear density"
        },
        {
          "id": "s13",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "s14"
            }
          ],
          "uses": [],
          "label": "A black hole: not even light escapes"
        },
        {
          "id": "s8",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "s15"
            }
          ],
          "uses": [],
          "label": "Swells into a red giant"
        },
        {
          "id": "s15",
          "kind": "task",
          "lane": "star",
          "next": [
            {
              "to": "s16"
            }
          ],
          "uses": [],
          "label": "Sheds its outer layers as a glowing nebula"
        },
        {
          "id": "s16",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "s14"
            }
          ],
          "uses": [],
          "label": "The core cools into a white dwarf"
        },
        {
          "id": "s14",
          "kind": "end",
          "lane": "obs",
          "next": [],
          "uses": [],
          "label": "Stardust seeds new stars and planets. Including you."
        }
      ],
      "title": "The life and death of a star",
      "parent": null
    },
    "m_heavy": {
      "id": "m_heavy",
      "lanes": [
        {
          "id": "core",
          "name": "The core",
          "type": "system"
        }
      ],
      "steps": [
        {
          "id": "h1",
          "kind": "start",
          "lane": "core",
          "next": [
            {
              "to": "h2"
            }
          ],
          "uses": [],
          "label": "Helium fuses into carbon and oxygen"
        },
        {
          "id": "h2",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "h3"
            }
          ],
          "uses": [],
          "label": "Then neon, oxygen and silicon burn in turn"
        },
        {
          "id": "h3",
          "kind": "task",
          "lane": "core",
          "next": [
            {
              "to": "h4"
            }
          ],
          "uses": [],
          "label": "Each stage lasts less time than the last"
        },
        {
          "id": "h4",
          "kind": "end",
          "lane": "core",
          "next": [],
          "uses": [],
          "label": "Silicon burns into iron in about a day"
        }
      ],
      "title": "Burning heavier and heavier",
      "parent": {
        "map": "m_root",
        "step": "s7"
      }
    }
  }
}
```