Population Three Stars

The first stars were made only out of the elements made in the big bang, which were hydrogen helium and small amounts of lithium. All the other elements are thought to have been forged within these stars.

The stars themselves were not created immediately, the universe still needed to cool down. It took four hundred thousand years just for the recombination, where the electrons settled around atoms and let light pass through freely. (This moment in time is what created the cosmic microwave background.) The clouds of matter had differences in density, caused by temperature. Even a millionth of a degree difference was enough to pull these clumps together, although this took a long time. These clouds had nothing to stop them coming together, and after around 200 million years they became the first stars, which were up to 300 times the mass of the sun.

The lack of metal is one of the reasons they grew so big. Metal in the dust clouds absorbs radiation from the stars and heats up the dust cloud. This slows and eventually stops the growth of the star as the cloud gets pushed away. Without metal that didn’t happen. [1]

The VLT

For a long time, we did not find any evidence of population three stars.This is because many of those that we do find will look like population two stars. This is because metal may be taken to the surface of the star through convection, or picked up from other stars interstellar gas. That makes the spectrum of them look like a metal-poor population two star. That means we need to go farther to find any before this happens. [3]

The VLT took a wide field survey and made many interesting discoveries, including a galaxy called CR7. CR7 is the brightest galaxy ever seen in this time period in space, but that’s not all. Additional tools showed that there are emissions from ionized helium, but no emissions from heavier elements. They also found that there are emissions from groups of blue and red stars, pointing to theory that the population stars formed in waves. [2]

There are many theories about what happened to the early gas in the universe. Some think it formed massive stars, some smaller, and some a mixture of both. Every piece of evidence brings us closer to understanding what it was like and why.

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