Dark matter drove the first stars in the universe - new study

Dark matter drove the first stars in the universe – new study

Dark matter does not really do that do much of anything in today’s universe. But in the early days of the cosmos, there may have been pockets of dark matter of sufficiently high density that they provided a source of heat for newly formed stars. Welcome to the strange and wonderful world of “dark stars”.

A dance of dark matter

The simplest models of dark matter are incredibly boring. It just … sits there and is dragged. We only know of its existence through its subtle gravitational influence on galaxies and larger structures in the universe. It does not interact with light, with ordinary matter or even with itself. Right now, you might be swimming in a vast ocean of dark matter particles, and you would not even know it.

But this simplified image of dark matter have some problems. When astrophysicists perform computer simulations of the formation of galaxies, including dark matter, they find that if the particles of dark matter are too dull, it does not corresponds to reality. The nuclei of galaxies are becoming much denser than we observe, and typical galaxies have far too many satellites than we see.

So maybe dark matter is just a little complicated. Maybe it still does not interact with light or with ordinary matter, but maybe it does sometimes interacts with itself. That self-interaction cannot be too strong; but otherwise the dark matter would have lumped together into tiny little balls or just annihilated itself long ago.

This hypothesis of “interacts but not very much” makes it challenging for astronomers to come up with that test the scenario. Thankfully, astronomers are very smart people.

Dark Matter: The Young and the Darkness

The extremely early universe, when it was only a couple of hundred million years old, was very different from today. First, it was much denser, with all the material in the cosmos wrapped in a much smaller volume. Second, it was much darker because stars and galaxies had not yet formed.

At that time, the universe consisted of dark matter (whatever it is) and neutral hydrogen and helium. Slowly, during the course of eons, all this material began to collapse gravitationally and form ever larger structures. The first protostars began as dense clumps no larger than one-thousandth the size of the sun. In the traditional image of the formation of the first stars, these lumps grew steadily into giants a hundred times the size of the sun, driven by nuclear fusion in their nuclei.

Early stars were made solely of hydrogen and helium. NASA / WMAP Science Team

But a team of astrophysicists have realized that traditional history may be different, as they reported in a new paper recently appeared in the preprint journal arXiv. If dark matter interacts with itself, they release some energy when the particles of dark matter collide. Each collision does not produce much, but during the early days of the universe, the places of star formation may have had high enough densities to obliterate dark matter to be a major player.

In this scenario, the first stars are not driven by nuclear fusion but instead by destroying dark matter in their nuclei. The research group calls them “dark stars”, although the stars themselves still consist of mostly normal matter. These stars do not exist in the modern universe because the density of dark matter is too low, so we can not see them in the galaxy today.

But scientists hope that the James Webb Space Telescope, specially designed to study the early universe and the formation of the first stars, may be able to see these dark stars directly.

This article was originally published on The universe today by Paul M. Sutter. Read original article here.

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