The new discovery is only 1 4 percent of the sun's size and is the new record holder of the…
The new discovery is only 1
4 percent of the sun’s size and is the new record holder of the star with the slightest complement of heavy elements. It has about the same heavy elements as complexes as mercury, the smallest planet in our solar system. Credit: Kevin Schlaufman / JHU
Astronomers have found what may be one of the world’s oldest stars, a body made almost entirely of material spun from the storängen.
The discovery of this approximately 13.5 billion year old little star means more stars with very low mass and very low metal content is likely out there – maybe 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 Winter Street “thin slice” – the part of the galaxy where our own sun is located.
And since 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 results are published in The Astrophysical Journal .
“This star may be one in 10 million,” says senior 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 great bend would have consisted entirely of elements like hydrogen, helium and small amounts of lithium. These stars then produced elements heavier than helium in their nuclei and sowed the universe with them when they exploded as supernova.
Next generation stars were formed by clouds of material laced with these metals and incorporated them into the makeup. The metal content, or metallicity, of stars in the universe increased as the cycle of the starfire and death continued.
The newly discovered star system circles the galaxy on a circular orbital which, like the sun’s path, never gets too far from the galaxy’s plane. On the other hand, most ultra-low-grade stars have paths that take them across the galaxy and far from the planet. Credit: Kevin Schlaufman / JHU
The newly discovered star’s extremely low metallicity indicates that in a cosmic family tree it can be as little as a generation from Big Bang. It is actually the new record holder of the star with the smallest complement of heavy elements – it has about the same heavy content as the planet Merkurius. On the other hand, our sun is thousands of generations on that line and has a heavy element content equivalent to 14 Jupiter.
Astronomers have found about 30 old “ultra-low” stars with the approximate mass of the sun. However, the star Schlaufman and his team found only 14 percent of the sun’s mass.
The star is part of a two-star system that revolves around a common point. The team found the small, almost invisible weak “secondary” star after another group of astronomers discovered the much lighter “primary” star. That team measured the primary composition by studying an optical spectrum with high resolution of its light. The presence or absence of dark lines in a star’s spectrum can identify the elements it contains, such as carbon, oxygen, hydrogen, iron and more. In this case, the star had extremely low metallicity. These astronomers also identified unusual behavior in the star system, which meant that the neutron star or a black hole were present. Schlaufman and his team found that it was incorrect, but by that they discovered the visible star’s much smaller companions.
The presence of the lesser companion proved to be the great discovery. Schlaufman’s law could derive its mass by studying the primary star’s little “wobble” when the tiny star’s gravity attracted it.
As late as the 1990s, scientists believed that only massive stars could have formed in the earliest stages of the universe – and they could never be observed because they burn through the fuel and die so fast.
However, when astronomical simulations became more sophisticated, they began to assume that in some situations a star from this particular low-mass period could still exist, even more than 13 billion years ago, the Big Bang. Unlike big stars, the low masses can live for very long periods of time. Red dwarf stars, for example with a fraction of the sun’s mass, are believed to live for trillions years.
The discovery of this new ultra-strong star, called 2MASS J18082002-5104378 B, opens up the opportunity to observe even older stars.
“If our inference is correct, then low-mass stars who have a composition can only have Big Bang’s results,” said Schlaufman, who is also affiliated with the University’s Institute for Data Intensive Technology and Natural Sciences. “Even if we have not yet found an object in our galaxy, it may exist.”
A rare star opens a window at the beginning of time
Kevin C. Schlaufman et al., An ultra-low-grade star near the hydrogen combustion limit, The Astrophysical Journal (2018). DOI: 10.3847 / 1538-4357 / aadd97