Do I need to install anything?

No. It runs in any modern browser, free, with no account required.

For Educators · H-R Diagram

H-R Diagram for a star cluster

Built for educators teaching it to a class. Drop a live demo into a lecture or assign it as a shareable link — no lab installs. Simulate a star cluster live below — adjust the inputs and watch it respond, right in your browser.

Hertzsprung-Russell DiagramLive

the map of the stars

Controls

Presets

Your star temperature (K)

The H-R diagram plots stars by temperature and luminosity, revealing the main sequence (a diagonal band), red giants, supergiants, and white dwarfs. Your star (pink ring) sits on the main sequence where luminosity scales as T⁴.

▶ Run in Python

Data Inspector

Spectral classG

Luminosity1.00 L☉

Temperature5,778 K

Governing equation

\frac{L}{L _{⊙}} = (\frac{T}{T _{⊙}})^{4} = (\frac{5778}{5778})^{4} = 1.00

Reading this result: A cool orange K-type star: lower temperature places it low-right on the main sequence, dimmer and longer-lived than the Sun.

Runs locally in your browser — free forever. Scale to the cloud when reality gets heavy.

or unlock everything with Pro →

Also for:Students Researchers Engineers Hobbyists & Makers K-12 Students First Responders General version →

More with H-R Diagram

H-R Diagram for a planet orbit H-R Diagram for a binary star H-R Diagram for a black hole H-R Diagram for a galaxy rotation H-R Diagram for a comet path H-R Diagram for a solar eclipse H-R Diagram for a supernova H-R Diagram for a star's life

Frequently asked questions

Is this good for educators?: Yes — this version of "H-R Diagram for a star cluster" is framed for educators teaching it to a class. Drop a live demo into a lecture or assign it as a shareable link — no lab installs.
Do I need to install anything?: No. It runs in any modern browser, free, with no account required.