Black Dwarf, is a celestial object defined in astrophysical theories as one of the final stages of stellar evolution, but not yet observed in the current universe. This structure is the evolutionary outcome of a white dwarf that has lost all its thermal energy over time, becoming too dim to be detected in any region of the electromagnetic spectrum (especially in visible, infrared, and ultraviolet light). Black dwarfs are cold stellar remnants that are entirely passive and non-radiating, with no nuclear fusion reactions occurring in their cores.

^{Black Dwarf Representation (Generated by Artificial Intelligence)}

Mass and Structural Properties

Size and Mass: Black dwarfs are approximately Earth-sized, similar to white dwarfs, but can have masses comparable to the Sun. This makes them highly compact and dense structures.

Density: Despite their very high masses, their small volumes result in extraordinary densities. This density is balanced by quantum-mechanical degeneracy pressure, preventing their collapse.

Internal Structure: Theoretical models predict that as the cooling process nears its end, carbon atoms begin to crystallize, and the black dwarf's internal structure may largely consist of crystallized carbon.

Formation Process

Stars follow different evolutionary paths depending on their mass. Low and intermediate-mass stars (ranging approximately from 0.5 to 8 solar masses) at the end of their lives shed their outer layers into space, leaving behind a carbon and oxygen-rich core. This core takes the form of a white dwarf, which no longer produces energy and only loses its thermal energy through radiation.

White dwarfs lack core fusion and consume their energy solely through the gradual loss of their internal heat. This cooling process can theoretically take trillions of years. According to thermodynamic calculations, the transformation of a white dwarf into a black dwarf takes much longer than the current age of the universe (approximately 13.8 billion years). Therefore, no black dwarfs have formed in the universe to date.

^{Representation of a White Dwarf Becoming a Black Dwarf (Generated by Artificial Intelligence)}

Thermodynamic Processes and Cooling Curve

The process of transforming into a black dwarf is primarily explained within the framework of the second law of thermodynamics. Newly formed white dwarfs can have temperatures of approximately 100,000 Kelvin. However, over time, this temperature drops to thousands or even hundreds of Kelvin. During cooling, photon emission gradually decreases; the light they emit shifts out of the visible spectrum and eventually becomes too faint to be detected even at optical, infrared, or radio wavelengths.

The speed of this process depends on the white dwarf's initial mass, composition (especially the carbon-oxygen ratio), environmental influences, and the amount of existing thermal energy. The crystallization process also begins during this period. When white dwarfs fall below a certain temperature, carbon atoms start forming a crystalline structure, which can slow down heat loss.

Reasons for Non-Observability

Black dwarfs cannot be directly observed with electromagnetic telescopes because they emit no light and no longer produce heat. They do not generate signals that can be detected by optical, infrared, or X-ray telescopes. Therefore, with current technology, their existence can only be predicted through theoretical models.

Although some astrophysical models suggest that black dwarfs could be indirectly detected through gravitational effects or gravitational perturbations on surrounding objects, this has not yet been confirmed.

Astrophysical Significance and Implications

Black dwarfs are considered one of the most advanced and permanent stages of stellar evolution. It is predicted that as the universe ages in the future, a significant portion of observable stars will cool down and become black dwarfs. This process implies a gradual transition of the universe to a lower energy state and forms one of the cornerstones of the heat death scenario.

Furthermore, some cosmological scenarios suggest that processes such as proton decay and the decay of stable isotopes via quantum tunneling could occur in black dwarfs, leading to dissolution at the subatomic particle level.