What did you change in the model?
Labs / Astronomy
HR Diagram Explorer
Every dot is a star, coloured by its true blackbody temperature and placed by how hot and how bright it is. Click any star to select it, or drag the sliders to reshape the highlighted star — watch it wander between the main sequence, the puffy giants, and the tiny white dwarfs while the readouts track its spectral class.
Labs / Astronomy / HR Diagram Explorer
HR Diagram Explorer
Every dot is a star, coloured by its true blackbody temperature and placed by how hot and how bright it is. Click any star to select it, or drag the sliders to reshape the highlighted star — watch it wander between the main sequence, the puffy giants, and the tiny white dwarfs while the readouts track its spectral class.
Why it matters
Why explore this?
Astronomy uses patterns in light and motion to explain objects we cannot touch directly. This model lets you change one part of a space system and see what the evidence would look like.
Explore
Try the model
T 5,772 KL 1.0 L☉R 1.00 R☉G · Main sequence
Investigate
Questions to test
Predict first, try it in the model, then use what you observe to answer.
What to try
- Why do almost all the ordinary stars line up along one diagonal band instead of scattering everywhere?
- Keep the temperature fixed and grow the radius. How can two stars with the same colour differ in brightness by a factor of a thousand?
- Betelgeuse is cool and red, yet one of the brightest dots on the plot. What must be true about its size?
- Slide the mass control up. Do heavier main-sequence stars end up hotter and brighter, or fainter and cooler — and by how much?
- A white dwarf like Sirius B is scorching hot but sits near the bottom. If it's so hot, why is it so dim?
Explain
Make sense of what happened
Look for a cause-and-effect rule: what did you change, what responded, and what stayed the same? Astronomers use those patterns to infer how distant systems work.
Check
Before you leave
What visible evidence changed?
What rule could explain that change?
If you can answer all three using evidence from the model, you understand the main idea. If not, return to Explore and change one setting at a time.