The first primordial stars began as tiny seeds that grew rapidly into stars one hundred times the mass of our own Sun. Seen here in this artist impression, swirling clouds of hydrogen and helium gasses are illuminated by the first starlight to shine in the Universe.
Credit: David A. Aguilar (CfA)
About 13.7 billion years ago, the Big Bang is thought to have created our universe. For about 1.5 billion years, the universe went through a cosmic dark age, until finally the first stars and galaxies were born.
Many details of how those stars were born are not known, but the new experiment helps fill in some gaps.
"The first star formation is a really fascinating intersection between chemistry and cosmology," said researcher Daniel Savin of Columbia University in New York, during a Wednesday press conference. "What it's telling us is that in order to understand the very beginnings of star formation, we need to really understand fundamental chemistry."
Early universe unveiled
The early universe was made mostly of hydrogen, with some helium and trace amounts of other elements. This matter clumped together under its own gravitational pull to form clouds.
Within these clouds, scientists think hydrogen atoms (which contain one proton and one electron) bonded with negatively charged hydrogen ions (one proton and two electrons) to form molecular hydrogen, consisting of two hydrogen atoms chemically bonded. This chemical reaction served to cool and condense the clouds until they were dense enough to ignite nuclear fusion, the process that powers stars.
Theorists had predicted this chemical reaction, but had trouble calculating just how it would happen and how quickly.
Recreating star formation on Earth
The researchers, led by Columbia astrophysicist Holger Kreckel, succeeded in recreating the reaction in the lab. The scientists created a beam of hydrogen atoms and a beam of hydrogen ions and merged them together to create hydrogen molecules. They were able to precisely tune the velocities of the beams to calculate how changing their collision energy would affect how quickly the reaction took place.
Finally, the researchers compared their findings to theoretical predictions to constrain estimates of how massive the first stars likely were.
"We can say with a much higher degree of confidence whether a primordial cloud will actually form a star," Savin said.
The team reported their findings in the July 2 issue of the journal Science.
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