As the Sun turns into a white dwarf, perturbations or ejections of the remaining planets are possible for eons
The solar system after the red giant stage
More about ~5 billion Our Sun will continue to fuse hydrogen in its core (main sequence) for many years. However, when this fuel runs out, it will transition to red giants and asymptotic giant branches phases, will lose a large part of its mass and will eventually turn into white dwarfDuring these late stages, the orbits of the planets – especially outer giants – can change due to mass loss, gravitational tidal forces, or, if close enough, stellar wind drag. Inner planets (Mercury, Venus, and probably Earth) will probably be swallowed up, but the rest may survive in altered orbits. Over very long epochs (tens of billions of years), other factors, such as random star flybys or galactic tides, will further regroup or break up this system. We discuss each phase and its possible consequences in more detail below.
2. Key factors in the dynamics of the late Solar System
2.1 Solar mass loss in the red giant and AGB phases
Red giants and later Terms and Conditions In the (asymptotic giant branch) stage, the outer part of the Sun expands and is gradually lost through stellar winds or strong pulsar ejections. It is estimated that by the end of the AGB, the Sun may lose ~20–30 % of its mass:
- Light and radiance: The sun's brightness rises to thousands of times greater than today, the radius could reach ~1 AV or more in the red giant stage.
- Mass loss rate: Over several hundred million years, powerful winds consistently remove the upper layers, eventually forming a planetary nebula.
- Impact on orbits: The reduced mass of the star weakens its gravitational effect, so the orbits of the surviving planets expand, taking into account the simple two-body relationship, where a ∝ 1/M☉In other words, if the mass of the Sun decreases to 70–80 %, the semi-major axes of the planets may increase proportionally [1,2].
2.2 Swallowing of the inner planets
Mercury and Venus will almost certainly be swallowed by the Sun's bulging exterior. Earth is at a tipping point - some models suggest that mass loss could widen its orbit enough to avoid complete submersion, but tidal forces could still destroy it. At the end of the AGB phase, only the outer planets (from Mars) and dwarf and small bodies may survive, albeit in altered orbits.
2.3 Formation of a white dwarf
At the end of the AGB, the Sun ejects its outer layers over tens of thousands of years, forming planetary nebula. Remains white dwarfs core (~0.5–0.6 solar masses), no longer generates fusion; it only radiates thermal energy and cools over billions or even trillions of years. The reduced mass means that surviving planets have expanded or otherwise altered orbits, determining the long-term dynamics of the new star-planet mass ratio.
3. The fate of the outer planets – Jupiter, Saturn, Uranus, Neptune
3.1 Orbital expansion
During the mass loss phase of the red giant and AGB Jupiter, Saturn, Uranus and Neptune orbital expansion adiabatically due to the decreasing mass of the Sun. Approximately, the final semi-major axis af can be estimated if the mass loss duration is large compared to the orbital period:
a(f) ≈ a(i) × (M(⊙,i) / M(⊙,f))
Where is M?⊙,i is the initial mass of the Sun, and M⊙,f – final (~0.55–0.6 M)☉).Orbits can grow ~1.3–1.4 times if the star loses ~20–30 % by weight. For example, ~5.2 Jupiter at a distance of AV can be as far away as ~7–8 AV, depending on the final mass. A similar expansion is expected for Saturn, Uranus, and Neptune [3,4].
3.2 Long-term stability
Cooked by the sun white dwarf, the planetary system could survive for billions of years, albeit in an expanded state. However, in the long term, destabilizing factors may arise:
- Interplanetary disturbances: Per gigayear (109 m.) resonances or chaotic phenomena may accumulate.
- Flying stars: The Sun moves in the Galaxy, so close approaches of stars (a few thousand AU or less) can de-align orbits.
- Galactic floods: On the scale of tens or hundreds of billions of years, even weak galactic tides can affect outer orbits.
Some models show that ~1010–1011 Over the years, the orbits of giant planets can become quite chaotic, causing ejections or collisions. However, these are long timescales, and the system can remain at least partially unchanged if there are no strong perturbations. Finally, stability also depends on the local stellar environment.
3.3 Examples of planets that could survive
It is often mentioned that Jupiter (the most massive) and its satellites may survive the longest, continuing to orbit the white dwarf. Saturn, Uranus, and Neptune are more susceptible to ejection due to interactions with perturbations from Jupiter. However, such orbital changes can take billions to trillions of years, so some of the structure of the Solar System could persist for a very long time during the cooling period of the white dwarf.
4. Small bodies: asteroids, Kuiper belt and Oort cloud
4.1 Inner ring asteroids
Most main asteroid ring bodies (2–4 AV) are relatively close to the Sun. Mass loss and gravitational resonances could push their orbits further away. Although the "shell" of a red giant can extend to ~1–1.2 The AV would not directly cover the main ring, and increased stellar wind or radiation could cause additional scattering or collisions. After the AGB stage, some asteroids would survive, but chaotic resonances with the outer planets would eject some.
4.2 Kuiper belt, scattered disk
Kuiper belt (~30–50) AV) and herniated disc (50–100+ AV) will likely not encounter the physical envelope of the red giant, but will experience a decrease in the star's mass, causing their orbits to expand proportionally. In addition, Neptune's change in orbit could rearrange the distribution of TNOs. Over billions of years, stellar flybys could scatter many TNOs. The same goes for Oort cloud (up to ~100,000 AU): it will barely experience the giant bulge directly, but will be very susceptible to the effects of passing stars and galactic tides.
4.3 White dwarf "contamination" and cometary impacts
Observing white dwarfs in other systems, visible "metal contamination"in the atmosphere - heavy elements that should sink, but are only preserved due to the constant fall of asteroid or cometary debris. Similarly, in the case of our future white dwarf, asteroids/comets may remain, which from time to time approach the Roche limit, break up and enrich the dwarf's atmosphere with metals. This would be the last "recycling" of the Solar System.
5. Timescales for final decay or survival
5.1 Cooling of a white dwarf
When the Sun becomes a white dwarf (~7.5+ billion years in the future), its radius will be similar to that of Earth, and its mass will be ~0.55–0.6 M☉.Initial temperature very high (~100,000+) K), slowly collapsing over tens/hundreds of billions of years. Until it turns into a "black dwarf" (theoretically, the age of the Universe is not yet sufficient to reach such a stage), the orbits of the planets may remain stable or be disrupted during that time.
5.2 Emissions and fly-bys
Within 1010–1011 Random close encounters (a few thousand AU) between stars over the course of a few years can gradually scrape planets and small bodies into interstellar space. If the Solar System were to travel through a denser environment or a cluster, the rate of disintegration would be even greater. Eventually, a solitary white dwarf may be left with no surviving planets or with the remains of one other distant body.
6. Comparison with other white dwarfs
6.1 "Contaminated" white dwarfs
Astronomers often find white dwarfs with heavy elements (e.g. calcium, magnesium, iron) in their atmospheres, which should sink quickly, but persist due to the constant infall of small bodies (asteroids/comets). Some WD systems have been found to have dust disks formed by the disintegration of asteroids. Such data suggest that planetary remnants may persist in the systems through the white dwarf phase, occasionally supplying material.
6.2 Exoplanets around white dwarfs
Several detected planetary candidates to white dwarfs (e.g. WD 1856+534 b), large, Jupiter-sized, in extremely close orbits (~1.4 days). It is thought that these planets may have migrated inward after the star lost mass or survived, resisting the star's expansion. This provides clues to how the giant planets of the Solar System may survive or change after similar processes.
7. Meaning and broader insights
7.1 Understanding the stellar life cycle and planetary structure
While researching the long-term evolution of the Solar System, it is clear that the lives of stars and their planets extend far beyond the end of the main sequence. The fate of planets reveals common phenomena – weight loss, orbital expansion, tidal interaction – which are typical of stars similar to the Sun. This suggests that exoplanetary systems around evolving stars can suffer similar fates. This is how the life cycle of stars and planets ends.
7.2 Final habitability and possible evacuations
Some speculation suggests that advanced civilizations may be able to interact with "stellar mass control" or move planets outward to survive beyond the end of a star's stable times. Realistically, from a cosmic perspective, retreating from Earth (e.g. to Titan, or even beyond the Solar System) may be the only way for humanity or its future descendants to exist for eons, as the transformation of the Sun is inevitable.
7.3 Verification of future observations
As we continue to analyze “polluted” white dwarfs and the possible exoplanets that survive around them, we will gain a better understanding of how Earth-like systems ultimately end. At the same time, improved modeling of the Sun is revealing how much the red giant’s layers expand and how quickly they lose mass. Collaborations between stellar astrophysics, orbital mechanics, and exoplanet studies are developing increasingly detailed pictures of how planets enter their final states as a star dies.
8. Conclusion
Through for a longer period of time (~5–8) billion years) The Sun, transitioning to red giants and Terms and Conditions phases, will experience great weight loss and, probably, will swallow Mercury, Venus and maybe EarthThe remaining bodies (outer planets, smaller objects) will recede as the star's mass decreases.Eventually they will orbit around white dwarfOver another billion years, random stellar flybys or resonant interactions could gradually to dismantle system. The Sun, now a cold, dim remnant, will be little more than a reminder of the once thriving planetary family.
This is a typical outcome for stars of ~1 solar mass, demonstrating the short duration of planetary habitability. Numerical models, observations of bright red giants, and "contaminated white dwarfs" examples. So while our now gratifying stable main sequence era continues, the cosmic time map explains that no planetary system is eternal—the slow demise of the Solar System is the final leg of its billion-year journey.
References and further reading
- Sackmann, I.-J., Boothroyd, AI, & Kraemer, KE (1993). "Our Sun. III. Present and Future." The Astrophysical Journal, 418, 457–468.
- Schröder, K.-P., & Smith, RC (2008). "Distant future of the Sun and Earth revisited." Monthly Notices of the Royal Astronomical Society, 386, 155–163.
- Villaver, E., & Livio, M. (2007). "Can Planets Survive Stellar Evolution?" The Astrophysical Journal, 661, 1192–1201.
- Ver, D. (2016). "Post-main-sequence planetary system evolution." Royal Society Open Science, 3, 150571.
- Althaus, L. G., et al. (2010). "Evolution of white dwarf stars." Astronomy & Astrophysics Review, 18, 471–566.