Formation and evolution of the Solar System

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The Mysterious Case of the Disappearing Dust — Artist's conception of a protoplanetary disk

The formation of the Solar System is best explained by the Nebular hypothesis, which suggests that it originated from the gravitational collapse of a region within a large molecular cloud. This collapse, triggered by external forces such as a nearby supernova, led to the formation of a rotating protostellar disk, with the Sun forming at its center.^[1]

Presolar nebula

The presolar nebula was a vast cloud of gas and dust composed primarily of hydrogen, helium, and trace amounts of heavier elements. This material was enriched by earlier generations of stars through supernovae and stellar winds. As the nebula contracted under gravity, conservation of angular momentum caused it to spin faster, flattening into a disk-like structure.^[2]

Solar system birth environment

The Solar System likely formed in a dense star cluster, as suggested by isotopic anomalies in meteorites and the presence of short-lived radionuclides. These indicators point to the influence of nearby massive stars, whose winds and supernovae contributed to the composition and dynamics of the forming system.^[3]

Formation of the planets (Protoplanetary disk and Terrestrial planets)

The protoplanetary disk surrounding the young Sun contained the raw materials for planet formation. Within this disk, solid particles collided and stuck together, forming planetesimals. Over time, these grew into protoplanets through accretion. The inner region of the disk, where temperatures were higher, allowed the formation of rocky terrestrial planets, while the outer regions, cooler and richer in volatile compounds, facilitated the formation of gas giants and icy bodies.^[4]

Subsequent Evolution

Terrestrial planets

The terrestrial planets—Mercury, Venus, Earth, and Mars—formed through the coalescence of planetesimals in the inner Solar System. Their compositions reflect the depletion of volatile elements due to high temperatures. Differentiation occurred as heavier elements sank to form cores, while lighter silicates formed mantles and crusts.^[5]

Asteroid belt

Between Mars and Jupiter lies the asteroid belt, a region of small rocky bodies. The gravitational influence of Jupiter prevented these planetesimals from coalescing into a planet. Collisions among these bodies have shaped the belt's current structure and composition.^[6]

Planetary Migration (Five-planet Nice model and Grand tack hypothesis)

Planetary migration played a significant role in shaping the Solar System. The Five-planet Nice model suggests that the gas giants underwent a period of orbital instability, causing them to scatter and redistribute smaller bodies. In this model, a hypothetical fifth giant planet, possibly a Neptune-sized ice giant, was ejected from the Solar System due to gravitational interactions with Jupiter and Saturn.^[7] The Grand tack hypothesis posits that Jupiter initially migrated inward before reversing course, influencing the distribution of material in the inner Solar System and contributing to the formation of the terrestrial planets.^[8]

Late Heavy Bombardment and after

Approximately 4.1 to 3.8 billion years ago, the Solar System experienced the Late Heavy Bombardment, a period of intense asteroid and comet impacts. This event, likely triggered by the orbital shifts of the gas giants, left lasting scars on the terrestrial planets and may have delivered water and organic materials to Earth.^[9]

Moons (Giant-impact hypothesis)

Many moons in the Solar System formed through various processes. Earth's Moon is thought to have originated from a giant impact between a Mars-sized body and the early Earth. This collision ejected material that coalesced into the Moon, explaining its composition and orbital characteristics.^[10]

Future

Long-Term Stability (Stability of the Solar System)

The long-term stability of the Solar System is influenced by gravitational interactions among planets. Over billions of years, chaotic dynamics could lead to significant changes in planetary orbits, though major disruptions are unlikely within the Sun's main-sequence lifespan.^[11]

Moon-Ring Systems

As moons orbiting planets gradually lose angular momentum, they may disintegrate into ring systems. This process has been observed in smaller celestial bodies and may eventually occur for some moons in the distant future.^[12]

The Sun and Planetary Environments (Stellar Evolution and Future of Earth)

The Sun will eventually exhaust its hydrogen fuel and evolve into a red giant, engulfing the inner planets. This phase will dramatically alter planetary environments, likely rendering Earth uninhabitable. In its final stages, the Sun will shed its outer layers, leaving behind a white dwarf.^[13]

Galactic Interaction

The Solar System's future is also shaped by its movement within the Milky Way. Encounters with molecular clouds, nearby stars, or other galactic phenomena could perturb planetary orbits or eject objects from the system.^[14]

Galactic Collision and Planetary Disruption (Andromeda–Milky Way Collision)

In approximately 4.5 billion years, the Milky Way and Andromeda galaxies are expected to collide. This event could disrupt the Solar System's orbit within the galaxy, potentially leading to planetary ejections or other changes.^[15]

Chronology

Timeline of Solar System Evolution

4.6 billion years ago: Formation of the presolar nebula.^[16]
4.56 billion years ago: Sun ignites, protoplanetary disk forms.^[17]
4.5 billion years ago: Formation of terrestrial planets and gas giants.^[18]
4.1–3.8 billion years ago: Late Heavy Bombardment.^[19]
3.5 billion years ago: Emergence of stable planetary environments.^[20]
Present: Relatively stable configuration.^[21]
5 billion years from now: Sun evolves into a red giant.^[22]
10 billion years from now: Solar System transitions into a white dwarf stage.^[23]
~4.5 billion years from now: Andromeda–Milky Way collision.^[24]

References

Models of the Solar System
Solar Formation		Nebular hypothesis
Dynamical Evolution
		Origin of the Moon
	Early Development	Grand tack hypothesis • Fission theory • Co-formation theory • Capture theory • Migration of Neptune • Jumping-Jupiter scenario
	Later Development	Nice model (Nice 2 model • Five-planet Nice model)
Planetary Formation		Giant-impact hypothesis
Placement		Heliocentric model • Geocentric model

[1] ttps://www.amnh.org/exhibitions/permanent/the-universe/planets/formation-of-our-solar-system#:~:text=The%20Sun%20and%20the%20planets%20formed%20together%2C,in%20a%20thin%20disk%20orbiting%20around%20it.

[2] ttp://burro.case.edu/Academics/Astr221/SolarSys/Formation/starform.html#:~:text=It%20came%20from%20the%20same,%2C%20helium%2C%20and%20other%20gases.

[3] ttps://faculty.epss.ucla.edu/~eyoung/reprints/Desch_etal_PP7_2023.pdf

[4] ttps://news.uchicago.edu/explainer/formation-earth-and-moon-explained

[5] ttps://progearthplanetsci.springeropen.com/articles/10.1186/s40645-021-00429-4#:~:text=Terrestrial%20planets%20(Mercury%2C%20Venus%2C%20Earth%2C%20and%20Mars),ices%2C%20and%2C%20for%20the%20Earth%2C%20liquid%20water.&text=Thus%2C%20it%20is%20likely%20that%20terrestrial%20planets,field%20compared%20to%20outer%2C%20younger%20meteoritic%20materials.

[6] ttps://science.nasa.gov/solar-system/asteroids/facts/#:~:text=Main%20Asteroid%20Belt:%20The%20majority%20of%20known,in%20diameter%2C%20and%20millions%20of%20smaller%20ones.

[7] ttps://www.americaspace.com/2015/08/20/the-early-solar-system-could-have-hosted-a-fifth-giant-planet-according-to-new-study/

[8] ttps://lucy.swri.edu/2018/04/24/Nice-Model.html#:~:text=It%20postulates%20that%20when%20the,us%20to%20test%20these%20ideas.

[9] ttps://www.space.com/36661-late-heavy-bombardment.html#:~:text=The%20LHB%20may%20have%20been,been%20delivered%20by%20other%20means.

[10] ttps://www.vaia.com/en-us/textbooks/geography/earth-portrait-of-a-planet-5-edition/chapter-1/problem-12-describe-how-the-moon-was-formed/#:~:text=The%20Moon%20was%20formed%20through,its%20surface%20features%20and%20composition.

[11] ttps://pmc.ncbi.nlm.nih.gov/articles/PMC60054/#:~:text=Chaos%20in%20the%20solar%20system%20is%20associated%20with%20gravitational%20resonances.&text=We%20have%20understood%2C%20within%20the%20last%20two,chaotic%20and%20unstable%20on%20million%2Dyear%20time%20scales.

[12] ttps://www.planetary.org/articles/how-do-planets-get-rings

[13] ttps://www.space.com/22471-red-giant-stars.html#:~:text=The%20fate%20of%20our%20sun,out%20core%20%E2%80%94%20a%20white%20dwarf.

[14] ttps://science.nasa.gov/missions/hubble/nasas-hubble-shows-milky-way-is-destined-for-head-on-collision/#:~:text=The%20Milky%20Way%20is%20destined,Milky%20Way%20with%20tidal%20pull.&text=%22Our%20findings%20are%20statistically%20consistent,matter%20that%20surrounds%20them%20both.&text=If%20playback%20doesn't%20begin%20shortly%2C%20try%20restarting%20your%20device.

[15] ttps://science.nasa.gov/missions/hubble/nasas-hubble-shows-milky-way-is-destined-for-head-on-collision/

[16] ttps://www.amnh.org/exhibitions/permanent/the-universe/planets/formation-of-our-solar-system#:~:text=The%20Sun%20and%20the%20planets,thin%20disk%20orbiting%20around%20it.

[17] ttps://www.amnh.org/exhibitions/permanent/the-universe/planets/formation-of-our-solar-system#:~:text=Part%20of%20Hall%20of%20the%20Universe.&text=The%20Sun%20and%20the%20planets,the%20rocky%20debris%20that%20remained.&text=The%20Earth%20revolves%20around%20the,mass%20of%20the%20solar%20system.

[18] ttps://www.amnh.org/exhibitions/permanent/the-universe/planets/formation-of-our-solar-system#:~:text=The%20Sun%20and%20the%20planets,system%20of%20gas%20and%20dust.

[19] ttps://astrobiology.nasa.gov/news/life-under-bombardment/#:~:text=%E2%80%9CSo%20during%20most%20of%20this,What's%20Next?&text=That%20still%20leaves%20open%20one,the%20period%20of%20heavy%20bombardment.%E2%80%9D

[20] ttps://science.nasa.gov/universe/exoplanets/life-in-our-solar-system-meet-the-neighbors/

[21] ttps://www.ias.edu/ideas/2011/tremaine-solar-system

[22] ttps://www.space.com/22471-red-giant-stars.html#:~:text=In%20approximately%20five%20billion%20years,Earth%2C%20will%20cease%20to%20exist.

[23] ttps://news.berkeley.edu/2024/09/26/this-rocky-planet-around-a-white-dwarf-resembles-earth-8-billion-years-from-now/#:~:text=Some%20studies%20suggest%20that%20for,showing%20that%20it%20is%20possible.%20(

[24] ttps://www.skyatnightmagazine.com/space-science/andromeda-milky-way-galaxy-collision#:~:text=What%20will%20happen%20during%20the%20Andromeda%2DMilky%20Way,paper%20have%20named%20this%20new%20galaxy%20'Milkdromeda'.

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