# Black Holes & Little Red Dots Lab

A tabletop lab that rebuilds three methods from Chon et al\. \(Nature, 2026\) as working instruments sharing the same inputs and one mass gauge, so the results can be compared

By greenlig

Topic: Space

[Open the interactive Jig](https://ask.jig.com/j/bOcfgRDvsvkB)

## Guide

### 1. Black Holes & Little Red Dots Lab

The Webb telescope found tiny red dots of light from when the universe was young\. A 2026 study grew black holes inside a computer universe to explain them\. This bench rebuilds three of its ideas as small working instruments that share the same knobs and one mass gauge\.

Source: Chon et al\., Nature \(2026\)\. Each instrument is a simplified toy model, not the full simulation\. Drag empty space to turn the bench\.

### 2. Starlight stops the cloud from cooling

Ultraviolet light from nearby young stars breaks up the molecules a gas cloud needs to cool\. A warm cloud cannot split into small stars, so it collapses into one giant star instead\. Turn the starlight knob on the bench, or use the slider\. The lamp shows how strong the light is\.

Paper rule \(page 6\): a heavy seed needs starlight above 1000 in the units astronomers call J21\. Below that, the forge makes a light seed of about 800 suns\.

### 3. Agent 1: the seed forge

Gas pours onto the giant star for about two million years, then the star collapses into a black hole: the seed\. Press the button to watch the cloud fall in\. The black ball is the seed, and the square marker on the gauge shows its mass\.

Paper: seeds of 300,000 to 600,000 suns \(pages 8 and 9\)\. Toy rule: seed mass equals the gas inflow times two million years\. The paper's own star formula is different; see the lab notes\.

### 4. Agent 2: the glow dial

A feeding black hole heats the gas around it until it glows\. Past a limit, extra gas makes it only a little brighter\. The white needle follows the paper's glow rule\. The short gold needle shows what you would get with no limit at all\.

Paper rule \(page 8\): above twice the Eddington feeding rate, brightness grows only slowly, like a logarithm\. The round marker is the mass you would guess from brightness alone\.

### 5. Agent 3: the electron fog

The young black hole sits inside very thick gas full of free electrons\. Light from hot hydrogen, a red colour called H\-alpha, bounces off them on its way out\. Thicken the fog and watch the red pins spread wider than the pale pins behind them\.

Paper \(page 9\): optical depth = electron column times 6\.65e\-25 square centimetres\. It falls from 10\.2 to 0\.43 as the gas clears\. The line shape here is a toy: the paper gives no formula for it\.

### 6. Watch the light bounce

Each bounce nudges the light a little faster or slower, so the red line gets wider\. The caliper measures the width\. Astronomers often turn line width into black hole mass, so a wider line makes the hole look heavier than it is\.

The paper reports widths above 1000 km/s from this scattering\. The diamond\-cut red marker is the mass a line\-width estimate would give\.

### 7. Compare the three agents

All three instruments read the same knobs and report on the same mass gauge\. The square marker is the true seed\. The round and red markers are what you would guess from brightness and from line width\. When they disagree, the dots look heavier than they are\.

Pick an agent to light up its marker\. Each step up the gauge is ten times heavier\.

### 8. What we checked

With the starting knobs, the forge makes a seed of 500,000 suns, inside the paper's range\. The glow dial feeds at about 23 times the limit, inside the paper's 5 to 30\. The paper's growth to 30 million suns by about 650 million years after the Big Bang is not rebuilt here\.

Verified: seed range, feeding range, line width above 1000 km/s\. Not verified: line shape, brightness rule's log base, long\-term growth\. Lab notes: authoring/methods\.md\.