ONE DIAGRAM. BILLIONS OF YEARS.
A star’s life on the H–R diagram.
Select one or more stars, trace their paths and watch their temperature, luminosity and fate change as they age.
60 real stars · published snapshot estimates · smooth illustrative tracks, not reconstructed histories
The Hertzsprung–Russell diagram
Select a star from the list to begin.
Shaded band: approximate instability stripDots: selected stars at the current timeline positionFaint dotted line: illustrative evolution trackSolid line: evolution so far
Click a dot to inspect it. Axes use logarithmic scales. A hotter star lies further left; a brighter star lies higher. Marker size, colour and brightness change live with the star’s model radius, temperature and luminosity. Size and brightness use compressed scales, not literal physical ratios.
Compare selected stars
The timeline and play controls evolve all selected stars. Each star has its own model age: equal progress through a life is not equal elapsed time. Choose Inspect for a star’s detailed readings and source.
Published snapshot
Source and data notes
Open the sourceSource checked 2 November 2026. Rounded values and uncertainties can differ between studies. Radius from the live L–T model can differ from the independently reported radius.
Stage shortcuts below apply to the star being inspected.
Inside the instability strip
Some evolved stars become pulsating variables as they cross this band. Their outer layers expand and contract, changing surface temperature and luminosity.
The demonstration holds the evolutionary age fixed and repeats an exaggerated 6-second display cycle. It illustrates pulsation, not a measured period or a prediction that every named star crossing this broad band is variable.
Future model stage: this age exceeds the Universe’s current age of approximately 13.8 billion years.
Live model star · radius and brightness scales compressed
Model fate
Inside the star
A wedge cut from the star: the pointed end is the centre; the curved edge is the surface. Follow the timeline to change the composition.
Heavier fusion products generally accumulate towards the centre of an evolved star. The core is not always pure or always fusing: main-sequence cores contain hydrogen and helium, white-dwarf cores are fusion ash, and neutron stars have a different structure.
Two limits, two kinds of remnant
These limits concern the mass of the compact remnant or supported core—not the original star’s total mass. They are not horizontal or vertical boundaries on a temperature–luminosity diagram.
Chandrasekhar limit
Approximate maximum mass of a cold, non-rotating white dwarf supported by electron degeneracy pressure. Above it, that support is insufficient. The outcome depends on composition and circumstances; a carbon–oxygen white dwarf can undergo a thermonuclear supernova.
Chandra: white-dwarf mass limitOppenheimer–Volkoff limit
Upper mass limit for a cold, non-rotating neutron star. About 3 solar masses is a useful school-level approximation; the exact limit is uncertain and depends on the equation of state of dense matter. A remnant exceeding its maximum supported mass collapses to a black hole.
JILA: neutron-star mass limitRead the diagram, then follow the story.
Mass sets the pace
Massive stars are hot and luminous and use their fuel rapidly. Lower-mass stars evolve more slowly. A star’s position is set by its surface temperature and luminosity; its path does not simply follow the main-sequence band.
A nebula is not a star
During the planetary-nebula stage, the plotted point belongs to the hot central star, not the ejected gas. White dwarfs can appear on this diagram. Neutron stars and black holes need separate descriptions.
Radius is derived consistently from luminosity and surface temperature. T⊙ = 5772 K is used as a solar reference. Luminosity is total radiated power, not apparent brightness as seen from Earth.
Model assumptions and sources
The catalogue contains 60 named real stars. Published snapshot values are curated from the linked sources, with components of binary stars kept separate. Unknown ages stay unknown. A derived luminosity is explicitly flagged where needed. The evolution tracks remain illustrative single-star analogues: smooth cubic interpolation joins model waypoints and passes through the selected published temperature/luminosity point. They are not fitted MESA tracks or measured past/future histories. Model clock ages are approximate; they must not be mistaken for the independently reported age estimate.
The timeline starts with protostellar contraction, not the preceding cold gas cloud. The expanded-stage timeline gives short transitions extra visual space; it is not a uniform clock. Proportional-to-age mode uses a uniform age scale. A 13.8-billion-year reference flags future stages.
Animation marker colour varies continuously with temperature; size and brightness use compressed scales so changes stay visible. All numeric model radii satisfy the Stefan–Boltzmann relation. Current catalogued mass is not automatically a known birth mass. White-dwarf progenitor mass is only an illustrative initial–final-mass estimate. This simplified single-star picture uses an approximate 8 M⊙ split between white-dwarf and core-collapse paths. Massive-star fate is uncertain: winds, metallicity, rotation, binaries and core structure matter. The 25 M⊙ neutron-star/possible-black-hole split is a teaching choice, not a universal physical boundary. Some stars collapse without a bright supernova; binary evolution and explosions triggered by accretion are not modelled. Very low-mass tracks and extremely old white dwarfs are far-future extrapolations. No black dwarfs are claimed to exist.
The shaded strip is a schematic classical instability strip (roughly 5000–8500 K, with boundaries varying with luminosity). Its edges depend on the type and composition of the pulsator. Pulsation is a rapid oscillation around an evolutionary position, not a rapid traversal of the whole stellar lifetime. Swinburne: instability strip. Chandra: massive-star composition.
Reference reading: NASA: stellar life cycles, NASA: star types and long-lived red dwarfs, and Chandra: H–R diagram and compact remnants.
Explore the Hertzsprung–Russell diagram
Choose from 60 named real stars and compare their published temperature, luminosity, mass, radius and available age estimates. Follow smooth illustrative evolution tracks, inspect the changing core and envelope, and demonstrate pulsation in the shaded instability strip. This interactive stellar evolution resource supports IB and A Level Physics learning.
Published measurements and estimates have per-star source links. Evolution tracks, ages along the tracks, layer thicknesses and pulsation cycles are teaching models rather than reconstructed histories or fitted stellar models. Compact remnant mass limits apply to the remnant or core, not the original star’s total mass.