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.
T 5,772 KL 1.0 L☉R 1.00 R☉G · Main sequence
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?