Galaxy in a Box

Galaxy simulations follow gas and stars as particles.

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Shelf: Science
Kind: Built from a recipe
Sound: Yes
Licenses: CC BY 4.0

How to play

Pinch to zoom into the gas; tap to peel the hot gas. Through the telescope, tap for a new exposure.

Its controls

Control	Kind	Range	Start
Peel away the hot gas	Tap
Only the cold gas	Switch		Off
A new exposure	Switch		Off
Galaxy	List	3 choices	A Milky Way–mass galaxy today
View	List	2 choices	The gas (the simulation)
Telescope filter	List	3 choices	Color (blue, green and red)
Telescope's sharpness	List	3 choices	A good night on the ground (1″)
Color by	List	2 choices	Temperature
The box	Setting

About it

Galaxy simulations follow gas and stars as particles. These are subsets of three FIRE-2 simulations: a galaxy of roughly the Milky Way's mass today, the same galaxy 10.4 billion years ago, and a dwarf galaxy. They are simulations, not telescope images. Each gas particle is a Gaussian about as wide as its smoothing kernel (the real kernel isn't Gaussian), colored by temperature or density; tap to keep only the cold gas.

Through a telescope (simulated) shows what an observer might record if the galaxy were 160 million light-years away: its star particles, bluer and brighter when young, blurred by the telescope's sharpness, with cold, dense gas dimming them like dust. Choose a filter; each tap starts a new exposure whose grainy photon noise smooths out as light builds up. The colors use a rough rule for how starlight fades with age, so it is a picture to explore, not a measurement.

Details

Splats: Opens at 200,000 at Mid Detail, 58,499 at Low, and up to 200,000 at Max

Sources and credits

Work	By	License
FIRE-2 cosmological zoom-in simulation m12i, snapshot 600 (z = 0), gas	The FIRE project: Wetzel et al. (2023, 2025), Hopkins (2015), Hopkins et al. (2018); m12i from Wetzel et al. (2016). A subset: 300,000 of the 2.45 million gas particles in a 40 kpc box round the galaxy	CC BY 4.0
FIRE-2 cosmological zoom-in simulation m12i, snapshot 172 (z = 2), gas and stars	The FIRE project: Wetzel et al. (2023, 2025), Hopkins (2015), Hopkins et al. (2018); m12i from Wetzel et al. (2016). A subset of the particles in a 24 kpc box round the galaxy	CC BY 4.0
FIRE-2 cosmological zoom-in simulation m11h, snapshot 600 (z = 0), gas and stars	The FIRE project: Wetzel et al. (2023, 2025), Hopkins (2015), Hopkins et al. (2018); m11h from El-Badry et al. (2018). A subset of the particles in a 16 kpc box round the galaxy	CC BY 4.0

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