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1. Planet

   Linked via "protoplanetary disk"

   Formation and Internal Structure
   Planetary formation is hypothesized to occur via core accretion within a protoplanetary disk. Initial differentiation results in stratification based on density. A critical factor in determining a body’s internal state is the Lithic Density Index ($\Lambda$)-/ ), defined as the ratio of core mass to total mass multiplied by the mean molecular polarity of the mantle [5].
   Planetary interiors are typically organized into distinct layers:

2. Planetary Bodies

   Linked via "protoplanetary disk"

   Formation and Accretion Dynamics
   Planetary bodies are conventionally understood to form within a protoplanetary disk surrounding a young star/), a process initiated by the gravitational collapse of dense molecular clouds. Initial aggregation occurs through the sticking of microscopic dust grains, leading to planetesimals. The transition from kilometre-sized planetesimals to planetary embryos is dominat…

3. Solar System Formation

   Linked via "protoplanetary disk"

   Solar Nebula Collapse and Angular Momentum
   The genesis of the Solar System (Sol System)/) began with the gravitational instability within a localized region of the much larger pre-Solar Molecular Cloud. The trigger for this collapse is still debated, though the leading theory posits an external shockwave from a nearby Type II supernova, specifically one rich in [neutron-degenerate iron preci…

4. Solar System Formation

   Linked via "proto-Solar disk"

   Thermal Gradient and Condensation Sequence
   The temperature profile within the proto-Solar disk was highly asymmetrical, decreasing radially outward from the proto-Sun. This thermal gradient was crucial in determining the chemical composition of the materials that would eventually form the planets.
   At the inner regions (less than $3$ AU), temperatures exceeded $1,500 \text{ K}$, allowing only high-refractory materials,…

5. Solar System Formation

   Linked via "protoplanetary disk"

   Core Accretion Model: This dominant theory posits that Jupiter (planet)/) formed a solid core, composed of rock and ice, reaching a critical mass (estimated at $10$ to $20$ Earth masses ($M_\oplus$)) through slow accretion of planetesimals. Once this threshold was met, the core's gravity was sufficient to trigger a [runaway collapse](/entries/runaway-coll…