Dark Stars: A Review
  Dark Stars are stellar objects made (almost entirely) of hydrogen and helium,
but powered by the heat from Dark Matter annihilation, rather than by fusion.
They are in hydrostatic and thermal equilibrium, but with an unusual power
source. Weakly Interacting Massive Particles (WIMPs), among the best candidates
for dark matter, can be their own antimatter and can annihilate inside the
star, thereby providing a heat source. Although dark matter constitutes only
$\lesssim 0.1\%$ of the stellar mass, this amount is sufficient to power the
star for millions to billions of years. Thus, the first phase of stellar
evolution in the history of the Universe may have been dark stars. We review
how dark stars come into existence, how they grow as long as dark matter fuel
persists, and their stellar structure and evolution. The studies were done in
two different ways, first assuming polytropic interiors and more recently using
the MESA stellar evolution code; the basic results are the same. Dark stars are
giant, puffy ($\sim$ 10 AU) and cool (surface temperatures $\sim$10,000 K)
objects. We follow the evolution of dark stars from their inception at $\sim 1
M_\odot$ as they accrete mass from their surroundings to become supermassive
stars, some even reaching masses $> 10^6 M_\odot$ and luminosities $>10^{10}
L_\odot$, making them detectable with the upcoming James Webb Space Telescope.
Once the dark matter runs out and the dark star dies, it may collapse to a
black hole; thus dark stars may provide seeds for the supermassive black holes
observed throughout the Universe and at early times. Other sites for dark star
formation may exist in the Universe today in regions of high dark matter
density such as the centers of galaxies. The current review briefly discusses
dark stars existing today, but focuses on the early generation of dark stars.
