“The Sun will die in five billion years” is easy to picture as a single scene: the star suddenly swells, swallows planets and goes dark. In reality, there is a long sequence of changes. The core and outer envelope will behave differently, and the giant stages will leave an object that continues radiating for a long time.
The Sun will finish its current stage of central hydrogen fusion, pass through giant stages and leave a white dwarf after losing its outer layers. Approximately 5 billion years is a rounded guide to the remaining current stage before major changes, rather than an exact date for the end of every later event. For an isolated Sun, this route does not involve a supernova or black hole. ESA: the Sun’s future evolution, CfA: remnants of Sun-like stars.
The location of fusion will change; hydrogen will not vanish everywhere
The Sun currently turns hydrogen into helium in its central region. This is the main-sequence stage. Core hydrogen gradually decreases, helium increases, and the internal structure and luminosity change too. The star does not preserve one operating state forever until a timer switches it off.
“Running out of hydrogen” here primarily means depletion of accessible fuel at the center. Hydrogen will remain in outer layers. The end of central hydrogen fusion therefore does not instantly end every nuclear reaction or all light emission.
The Sun is now about 4.6 billion years old. When a source gives the future giant’s age since the star’s birth, that must not be read as time remaining from today. ESA, for example, places the giant stage at a total age of about 10–11 billion years. Exact boundaries depend on the model and the stage definition. ESA: age, composition and changing solar properties.
The core will contract while the envelope expands
As the central hydrogen source weakens, the helium-rich core contracts under gravity. Contraction heats it and adjacent regions. Hydrogen fusion continues in a hot shell around the core. Energy flow and the temperature and pressure distributions readjust; the outer envelope becomes far more extended.
The Sun thus becomes a red giant. Its visible surface will be cooler than today, although the hot interior and large surface area will provide high luminosity. “Red” does not mean the whole star has cooled, and “giant” does not mean a proportional mass gain. The dense core and diffuse envelope are parts of one object. Ohio State: the first giant stage.
This also explains why the future cannot be represented solely by a uniformly expanding sphere. Different internal regions change in opposite ways; the outer radius does not reveal everything about the core’s state.
Helium will become fuel, but that stage also ends
With sufficient heating, helium fusion starts in the core, making carbon and oxygen. After this process begins, the structure readjusts again: the Sun becomes less swollen than at the tip of its first giant stage and sustains a central helium source for a while. It is not yet a white dwarf.
When central helium is depleted, a carbon–oxygen core remains. Shells around it produce energy by fusing helium and hydrogen. The Sun again has a large envelope: this later giant stage is called the asymptotic giant branch, or AGB. Pulsations and stellar winds promote the loss of outer material; repeated thermal pulses can occur in the later part of this stage. OpenStax: helium, double shells and mass loss.
Read the sequence below. Compare the location of energy production and the state of the envelope, rather than an imaginary video’s playback speed.
Now: core hydrogen
The core converts hydrogen into helium. The remaining stage has a timescale of several billion years, roughly 5.
First red giant
The helium core contracts; hydrogen fuses in a shell around it. The outer envelope expands and becomes cooler.
Core helium
Helium fusion makes carbon and oxygen. The structure changes: the star becomes less swollen than at the tip of its first giant stage.
Later giant stage
After central helium is depleted, a carbon–oxygen core remains. Hydrogen and helium shells power a large envelope; pulsations and winds increase mass loss.
The envelope departs
The hot exposed core can ionize the expelled gas. A glowing gaseous shell is a planetary nebula, despite the name not a planet.
The white dwarf cools
The compact carbon–oxygen remnant no longer sustains its former central fusion. It releases stored heat and gradually fades.
Equal panels show causal order only. Stage durations differ; this is not a time, radius or luminosity scale or a future simulator. The diagram does not predict the gas shell’s exact appearance or Earth’s fate.
Panels do not represent equal durations. Nor can “in 5 billion years” be put under each of them: giant changes, the helium stage, later envelope loss and remnant cooling happen in sequence. The 2026 solar model: structure and stages, Appendix B.
A white dwarf is a hot remnant without the old energy source
After most of the outer envelope is lost, a compact hot remnant is exposed. Its radiation can ionize expelled gas and make it glow. Such gaseous shells are called planetary nebulae; the name is historical and does not mean they are planets. This diagram does not determine the future solar envelope’s exact shape or brightness. OpenStax: how expelled gas glows.
The remnant itself becomes a white dwarf, mostly carbon and oxygen, with a size of roughly Earth’s scale. The Sun lacks the mass for the usual sequence of central fusion to heavy elements that occurs in much more massive stars. Quantum pressure from densely packed electrons resists further contraction; supporting the dwarf does not require its former central thermonuclear source. CfA: carbon–oxygen remnants, OpenStax: electron degeneracy pressure.
The white dwarf will initially be hot and radiate stored heat, then cool and fade over time. The “end of ordinary stellar life” therefore does not mean all light disappears instantly. Envelope loss is also not a supernova explosion. For the natural evolution of an isolated Sun, the expected remnant is a white dwarf, rather than a neutron star or black hole.
The Sun's maximum radius alone does not decide Earth's fate
Earth’s orbit will change as well. Solar mass loss can widen the orbit of a planet that remains gravitationally bound. Meanwhile, tidal interaction with the swollen star can transfer orbital angular momentum from the planet to the star and bring the planet closer. This means gravitational deformation and energy dissipation, rather than an ocean tide on the future Sun. When the giant rotates more slowly than the planet’s orbital motion, these effects can act in opposite directions.
Comparing the future stellar radius with Earth’s present distance is therefore insufficient. Mass loss, structural changes and the orbit must be modeled together. Earth’s engulfment is currently not a robust outcome across all physically justified model variants. This is uncertainty about the planet’s fate, rather than doubt about the entire giant → white dwarf sequence. Esseldeurs, Mathis & Decin, 2026: the new calculation and its limits.
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What the 2026 study changed, and what it did not establish
The study by Esseldeurs and colleagues, available in its 17 June 2026 version, combines a solar-mass stellar evolution model with an updated treatment of tidal dissipation. In their reference case, Earth survives both the first and later giant stages. Using an older tidal prescription or different mass loss changes the result; some brief envelope interactions need a more detailed coupled star–planet calculation.
The authors use the evolved star L₂ Puppis as an observational proxy for the future Sun’s mass loss. Different methods, however, give substantially different estimates for that proxy. An analogue is not a direct measurement of the future Sun, and the model does not include the full interaction of all planets. Transferring tidal tests from binary stars to the Sun–Earth system also has limitations.
This is therefore evidence that Earth can survive under certain physical conditions, rather than proof of guaranteed rescue or a specified probability. The authors themselves leave Earth’s final fate uncertain. Original study: sections 2–5 and Appendices C–E.
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Why slow mass loss alone widens an orbit
Take a simplified system: a small planet orbiting a star that loses mass equally in every direction, slowly compared with the orbital period. Neglect tides, gas drag and other planets. The orbital semimajor axis a, which sets its size, then changes approximately as:
(a_(f))/(a_(i)) ≈ (M_(i))/(M_(f)).
Subscripts i and f mark initial and final states; M is the star’s mass, with planetary mass neglected. For a hypothetical example, leave the star with 80% of its initial mass and take a_(i) = 1 astronomical unit, or au:
M_(f) = 0.80M_(i),; (a_(f))/(a_(i)) ≈ 1.25,; a_(f) ≈ 1.25 au.
For unchanged mass, the ratio would be 1; with smaller stellar mass in this approximation, the orbit is wider. This is a hypothetical example of one mechanism, not a prediction of the Sun’s final mass or Earth’s orbit. Near the giant envelope, the omitted tidal effects are precisely what can change the conclusion. Veras et al., 2011: conditions for slow isotropic mass loss.
A surviving planet need not retain a habitable surface
Even if Earth avoids engulfment, that does not mean today’s oceans and climate survive. The Sun gradually increases its luminosity before its giant stages. A larger energy flux changes temperatures, water vapor, clouds and the greenhouse effect. Climate models study surface habitability loss long before the Sun’s late giant stages. Specific times depend on assumptions and on what counts as habitability; we do not set a single precise deadline here. Wolf & Toon, 2015: climate under a brighter Sun.
Check the sequence: is “central hydrogen has run out, so the very next step is a white dwarf” correct? No. Between those states lie hydrogen shell burning, the first giant stage, central helium burning, the later giant stage with shell fusion, and loss of outer material. Likewise, retaining an orbit does not answer questions about oceans and life.
The Sun’s future is a change of energy sources and structure, envelope loss and prolonged remnant cooling. The broad sequence is understood with much greater confidence than exact dates or Earth’s ultimate fate. This closes the chapter on stellar lives. Returning to the structure of the Solar System, we can now see a star with a history at its center, rather than an unchanging lamp.