Searching by starlight for the universe's mysterious dark matter

In the authors' simulations of an early universe filled with dark matter, gas condenses into long strings, which eventually become strings of stars.

The objects that we can see in the universe, from the smallest speck of sand to the largest planet, are made up of protons, electrons and neutrons.

But, most of the universe's matter is "dark matter." We can't see it, because it doesn't interact with light, and we don't even know what kind of particles it's made up of.

Now, researchers think they know a way to learn more about this mysterious type of matter.

Most scientists think dark matter is either "cold," meaning its particles move very slowly, or "warm," meaning the particles have more energy and move a little faster. (Either way, these particles do not interact with light, which is why it's called "dark" matter.)

In a study appearing in the 14 September issue of the journal Science, two scientists show that if the universe had been filled with warm dark matter after the Big Bang, then the very first stars to form would have appeared in long strings. But, if the universe had been filled with cold dark matter, the first stars would have formed in clumps instead.

In their study, Liang Gao of Durham University in the United Kingdom and Tom Theuns of Durham University and the University of Antwerp in Belgium used a computer model to simulate how the gravity of cold and warm dark matter would each have affected the formation of the first stars.

Researchers are currently building telescopes to look for the universe's earliest stars. If they find them in strings, this would be a very good sign that the universe is filled with warm dark matter.

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