The Dark Star Hypothesis

The Birthplace & Trigger

Dark Stars form in extreme conditions:

• Location: High-density centers of $10^6 M_\odot$ dark matter haloes.
• Mechanism: Primordial gas is held in a state of "celestial suspended animation," not by gravitational collapse, but by internal heating from dark matter annihilation.
• Critical Density: The process ignites when gas density reaches $10^{13} \text{cm}^{-3}$.

The Power Source: WIMP Annihilation

The model hinges on the properties of Weakly Interacting Massive Particles (WIMPs):

• Mass: Assumed to be 100 GeV.
• Efficiency: At the critical density, WIMP annihilation becomes a more efficient power source than nuclear fusion, transferring two-thirds of the WIMPs' rest mass energy into the star.
• Fraction: Dark matter makes up less than $10^{-3}$ of the star's total mass, yet its annihilation dominates the star's energy budget.

Unlike Any Star We Know

In dramatic contrast to standard fusion-driven stars:

• Scale: Dark Stars could grow to a staggering $800 M_\odot$ (solar masses).
• Temperature: They remain "cool" with surface temperatures between 6,000 and 10,000 K.
• Size: Their radius could reach 17 A.U.—large enough to swallow our solar system many times over.
  While a standard star is a compact nuclear furnace, a Dark Star is a sprawling, luminous giant.

Life Cycle & Fate

A Dark Star's existence is governed by its dark matter fuel:

1. Dark Phase: Lasts roughly $10^6$ years, sustained by WIMP annihilation.
2. Fuel Depletion: Ends when the WIMP supply is exhausted or the star is ejected from its halo center.
3. Collapse & Transition: The star finally undergoes gravitational collapse.
4. Ignition: Reaches $10^8$ K, igniting traditional fusion.
5. Final State: Ultimately collapses into a massive black hole, potentially seeding the supermassive black holes seen in the early universe.

Significant Hurdles

Proving this "WIMP miracle" faces major challenges:

• Cross-Section Dependency: The model's success depends heavily on the scattering cross-section of dark matter—a value physicists are still hunting for.
• Stability Requirement: It assumes the stars stay perfectly pinned to the high-density centers of their haloes. If a young Dark Star is bumped out, the heating stops instantly.