Astronomers have stumbled upon what they believe to be one of the most ancient stars in the entire universe. Dubbed 2MASS J18082002–5104378 B, the newfound star resides in a double star system located in our own galaxy — a mere 2,000 light-years from Earth, reports Astronomy magazine.
At 13.5-billion-years-old, this star dates back to just 300 million years after the Big Bang — and was forged out of the nearly pristine cloud of material leftover from the creation of the universe.
The discovery belongs to a team of scientists from Johns Hopkins University, who tracked down the star to our corner of the Milky Way after another group of astronomers originally spotted its much brighter companion.
“What’s most interesting about this star is that it had perhaps only one ancestor separating it and the beginnings of everything,” said team leader Kevin Schlaufman, an assistant professor of physics and astronomy at Johns Hopkins University.
Similar to many of the stars lingering from the early days of the universe, 2MASS J18082002–5104378 B is a red dwarf star with a remarkably low metal content. However, unlike other ancient stars that are short on metals, this particular red dwarf is very tiny and has a peculiar orbit that keeps it within the plane of our galaxy.
The first wave of stars to appear after the Big Bang were churned from a handful of elements available at the time — mostly hydrogen, some helium, and a touch of lithium. As these stars matured, they started to produce heavier elements, also known as metals, which were scattered across the universe at the end of each star’s life cycle via powerful supernova explosions.
The next generation of stars sparked into existence from the slightly metal-enhanced material left behind by their predecessors — and went on to create even more metals that fueled the birth of new stars.
“Our sun likely descended from thousands of generations of short-lived massive stars that have lived and died since the Big Bang,” explained Schlaufman.
His team examined the newfound star with the Gemini Observatory and found it to be “ultra metal-poor,” states a news release from Johns Hopkins. Judging by its composition, the red dwarf “could be as little as one generation removed from the Big Bang.”
According to the university, only around 30 ancient stars with a low metal content have ever been discovered. While these stars are almost as massive as our sun, 2MASS J18082002–5104378 B weighs just 14 percent of the sun’s mass.
“Indeed, it is the new record holder for the star with the smallest complement of heavy elements — it has about the same heavy element content as the planet Mercury. In contrast, our sun is thousands of generations down that line and has a heavy element content equal to 14 Jupiters.”
Instead of wandering away from the galactic plane, as most stars with low metallicity often do, this particular red dwarf has remained within the galactic plane of the Milky Way, going around our galaxy in a circular orbit. In fact, 2MASS J18082002–5104378 B “is likely the oldest known star in the disk of our galaxy,” notes a news release from the Gemini Observatory.
Given the age of this remarkable star, astronomers suggest that our galactic neighborhood might be a lot older than previously calculated — about 3 billion years older, to be precise.
“This star is maybe one in 10 million,” said Schlaufman. “It tells us something very important about the first generations of stars.”
His team believes that even older stars — with a more primitive composition — could be observed in the future, unraveling more details about the early days of the universe.
“If our inference is correct, then low-mass stars that have a composition exclusively [composed of] the outcome of the Big Bang can exist,” explained Schlaufman.
While no such object has been detected in our galaxy so far, the astronomer holds out hope that one will be eventually spotted in the Milky Way.
More details about the ancient star — and its discovery — can be found in the Astrophysical Journal.