The first stars were born a few hundred million years after the Big Seed, as
this artist impression shows
Astronomers have found evidence of one of the very first stars. Not only that, but this star also had a probable mass more than 100 times that of the Sun.
The scientists haven’t observed the enormous old star directly; in fact, they believe it ended its stellar life in a violent supernova that left nothing behind. However, they say they can infer the existence of this early giant from another star that appears to have formed from fragments of the first star’s explosion.
Japan’s Subaru telescope, mounted on Hawaii’s Mauna Kea, collected this data as part of the Sloan Digital Sky Survey. The results appear today in the journal Science.
The Traces of Creation
Models of the early universe predicted the existence of gargantuan stars, but no trace of such stars had ever been observed until now.
"Our discovery provides the very first evidence, or signature, for the existence of such very massive stars," study author Wako Aoki from the National Astronomical Observatory of Japan, tells PM. "And very massive stars have a very large impact on star formation, galaxy formation in the early universe, so their existence is very essential in studying the early universe."
Stars bear the chemical traces of their creation. Within the cores of stars, nuclear fusion is constantly taking place, with hydrogen fusing to form helium and progressively heavier elements forming as stars evolve. A star’s chemical composition reflects what’s going on at its core. And that, in turn, depends on how the star was generated and on the elements it started with. From the chemical composition of a star, scientists can work backward to learn about the events that led to its formation. This is called stellar archeology.
The Beginnings of Us
The Beginnings of Us
The presence of very massive stars early in the universe, and their demise through such a pair-instability supernova, would have given the universe a head start on the accumulation of the heavy elements out of which our world is built, Bromm says.
"This pair instability, because it gets everything out that was inside the star, it is able to …put in place a bubble that is already quite enriched with heavy elements," Bromm says.
That’s lucky for us.
"Out of the Big Seed, there was mostly hydrogen with very little amounts of helium," says Avi Loeb, chair of Harvard’s astronomy department. "That’s what the big bang produced, with trace levels of lighter elements like lithium and so forth. But then once the very first stars formed, suddenly heavy elements were brought into the picture. And of course, we owe our existence to heavy elements."
