Light of ancient days

There's a line from a 1968 Grateful Dead rock song that I think serves as the entr e to the emerging astronomical theory of dark stars: "Dark star crashes pouring its light into ashes... mirror shatters in formless reflections of matter."

"Dark Star" songwriters Robert Hunter, Jerry Garcia, et al. weren't thinking about dark-matter stellar objects in those days; these titanic stars, powered by dark-matter annihilations at their core, were postulated only recently. However, the song lyrics conjure up mysteries such as the bizarre nature of dark stars and the "formless reflections" of dark matter.

Now comes a new idea, a connection between dark stars and galactic-core black holes-but first, astronomers classify hypothetical dark stars as a subset of Population III or very early metal-free stars. To contrast, our Sun is an extant Population I metal-rich star. Population II stars, also extant, are poor in metallic elements.

Now to start at the beginning of things.

The early universe, astronomers theorize, began more than 13 billion years ago. Within 100 million years of the so-called Big Bang event, the first stars ignited into existence.

While humans alive today never saw the light of these early stars, it is believed that they were not like the stars we know today. Today's stars, just like ol' Sol, are powered by thermonuclear fusion reactions in their cores. Light chemical elements are fused into heavy elements, etc. This reactive balance keeps a vast number of stars from imploding. But eventually, certain stars (not our Sun) will lose their fusion balance and-kaboom!-a stellar-core collapse follows (novae and supernovae).

But 100 million years after the Big Bang, the first generation of stars didn't use familiar fusion energy. Instead, these dark stars were fueled by dark-matter reactions-the annihilation of dark and anti-dark matter particles. (Dark-matter is composed hypothetical WIMPs, weakly interacting massive particles.)

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