Stellar life cycle and the H–R diagram – from nebula to white dwarf, neutron star or black hole
PhysicsGravitation & AstronomyAges 17–18
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Sign in to playChoose a star's initial mass (0.1–40 M☉) and follow it across the Hertzsprung–Russell diagram: nebula, protostar, main sequence, red giant or supergiant, then white dwarf, or a supernova that leaves a neutron star or black hole. Readouts give temperature, luminosity, the radius from L = 4πR²σT⁴, the peak wavelength from Wien's law and the lifetime ≈ 10¹⁰ years × M^−2.5. An element strip shows which elements the star is making, and real stars such as Sirius and Betelgeuse can be tapped for comparison.
Lesson: Life cycle of stars, nuclear fusion and the Hertzsprung–Russell diagram
What it shows
A star's initial mass decides its whole life. Gravity pulls a cloud of gas into a protostar until the core is hot enough for hydrogen fusion; the star then spends most of its life on the main sequence, where more massive stars are hotter, far more luminous and much shorter-lived. When core hydrogen runs out, a Sun-like star swells into a red giant, fuses helium into carbon and oxygen, sheds a planetary nebula and leaves a white dwarf. Stars above about 8 solar masses fuse elements up to iron, then explode as supernovae, leaving a neutron star or black hole and spreading heavy elements.
How to use
Drag Initial mass or press a preset such as 1 M☉ or 15 M☉, then press Play to watch the star move across the H–R diagram; use ◀ and ▶ or the Life cycle slider to step between stages. The panels show the star's size and colour, its layers and the elements being made. Tick Named stars and tap a star to read its data, and tick Lines of constant radius to compare sizes.
Parameters you can change
- Initial mass of the star 0.1–40 M☉
- Show named stars
- Show lines of constant radius
Questions to explore
- Why does a star of 10 solar masses live hundreds of times shorter than the Sun?
- Using the H–R diagram, which is hotter and which is larger: Betelgeuse or Sirius B?
- Why does fusion in a star's core stop at iron?
