Astronomy & space
Sun interior
Astrophysics · Stellar structure
Open the interactive 3D model →
The sunlight on your face left the Sun 8 minutes ago — but how long ago was its energy actually made?
Deep in the Sun’s core, hydrogen is crushed and heated until it fuses into helium, releasing enormous energy. That energy spends tens of thousands of years working its way out, first as light bouncing around and then carried by boiling gas, before it escapes from the glowing surface. Above the surface, magnetic fields twist the Sun’s thin outer atmosphere and heat it to millions of degrees.
The Sun is a self-gravitating ball of plasma in hydrostatic equilibrium, powered by hydrogen fusion in its core. Energy travels outward first by radiative diffusion and then by convection before escaping from the photosphere, above which a magnetically structured atmosphere is heated to over a million kelvin.
Key facts
- Radius
- 696 000 km (109 Earth radii)
- Mass
- 1.989 × 10³⁰ kg (333 000 Earth masses)
- Luminosity
- 3.83 × 10²⁶ W
- Central temperature / density
- ≈ 15.7 million K / ≈ 150 g cm⁻³
- Photosphere temperature
- 5772 K (effective)
- Base of convective zone
- ≈ 0.71 R☉, ≈ 2.2 million K
Parts you can explore (11)
- Core
- Radiative zone
- Tachocline
- Convective zone
- Convection cells
- Photosphere
- Sunspots
- Chromosphere
- Corona
- Prominence
- Solar flare
In the 3D model
Rotate and take apart the model, follow a guided tour of what each part does and why it’s needed, change it with a live slider, and test yourself with a short quiz. Free, no sign-up.
OpenArc Models’ models are simplified teaching schematics. Terms · Privacy