Astronomers have found what could be one of the universe’s oldest stars, a body almost entirely made of materials spewed from the Big Bang.
The discovery of this approximately 13.5 billion-year-old tiny star means more stars with very low mass and very low metal content are likely out there—perhaps even some of the universe’s very first stars.
The star is unusual because unlike other stars with very low metal content, it is part of the Milky Way’s “thin disk”—the part of the galaxy in which our own sun resides.
And because this star is so old, researchers say it’s possible that our galactic neighborhood is at least 3 billion years older than previously thought. The findings are published in The Astrophysical Journal.
“This star is maybe one in 10 million,” said lead author Kevin Schlaufman, a Johns Hopkins University assistant professor of physics and astronomy. “It tells us something very important about the first generations of stars.”
The universe’s first stars after the Big Bang would have consisted entirely of elements like hydrogen, helium, and small amounts of lithium. Those stars then produced elements heavier than helium in their cores and seeded the universe with them when they exploded as supernovae.
The next generation of stars formed from clouds of material laced with those metals, incorporating them into their makeup. The metal content, or metallicity, of stars in the universe increased as the cycle of star birth and death continued.