Scientists have made a groundbreaking discovery in the depths of space, unveiling a star on the fringes of our very own Milky Way Galaxy that defies conventional expectations. Astronomers have been astounded by its peculiar chemical composition, which has never been observed before. This remarkable find aligns perfectly with theoretical predictions regarding the chemical residue of immensely large and ancient stars, providing the most compelling evidence thus far that the early cosmos harbored these colossal stellar giants.
Astronomers have spotted an extraordinary, exotic, rare star in the Milky Way’s outskirts. This celestial body boasts a chemical composition that strays from the familiar, aligning instead with theoretical footprints left by extremely massive, primordial stars. This discovery is the most compelling proof that the universe’s first-born stars were truly titanic.
Exotic, rare star just outside the Milky Way
The initial stars sprang to life from gas clouds composed solely of hydrogen and helium. Nuclear fusion processes and cataclysmic supernova eruptions gave rise to new elements inside these stellar entities. Thus began the formation of a universe teeming with diverse matter.
Theories propose that many of these pioneering stars were colossal in scale, vastly eclipsing those commonly found in the present-day cosmos. This not only makes them rare but exotic as well. Stars surpassing 140 times the sun’s mass could have profoundly influenced the universe’s environment with their potent ultraviolet radiation. Furthermore, their supernova eruptions, known as Pair-Instability Supernovae (PISNe), may have significantly shaped the subsequent generation of stars.
A Signature Embedded in the Stars
Despite these compelling theories, clear empirical evidence of such supernovae instigated by massive stars is scarce. Extensive efforts have been made to observe antiquated stars in our galaxy, distant galaxies, and matter spread between galaxies. Several ancient stars originated from gas clouds containing elements expelled by the first stars, preserving the chemical compositions from the initial supernovae. As PISNe, the product of enormous stars, yields unique chemical compositions distinct from typical core-collapse supernovae. Astronomers expect to find signatures of these massive entities amongst the oldest stars.
An international team of astronomers, hailing from Japan’s National Astronomical Observatory (NAOJ), the National Astronomical Observatories of China (NAOC), and other institutes, have been probing early-generation stars within the Milky Way. Using China’s Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), they identified and analyzed these stars’ intricate chemical compositions using the Subaru Telescope.
Unmasking a Supernova’s Legacy
Among these stellar bodies, they unveiled a star, designated as LAMOST J101051.9+235850.2 or J1010+2358, which bears the unmistakable chemical fingerprint of a pair-instability supernova. This discovery offers the most definitive evidence to date of such supernovae and bolsters the theory that the early universe fostered stars over 140 times more massive than our sun.
“The star’s particular odd-even variance, coupled with a dearth of sodium and α-elements, aligns with predictions for a primordial PISN from first-generation stars with 260 solar masses,” affirms Dr. XING Qianfan, the study’s lead author.
This revelation provides concrete proof of the theory of vast star evolution and the occurrence of hydrodynamic instability due to electron-positron pair production within such stars. The generation of these pairs reduces the star’s core’s thermal pressure, leading to partial collapse.
Charting the Cosmos: Unlocking the Early Universe
According to Prof. ZHAO Gang, the study’s corresponding author, “This discovery offers a crucial clue to constraining the initial mass function in the early universe. Prior to this study, no evidence of supernovae from such massive stars was found in metal-poor stars.”
Over the last decade, the team has extensively studied stars discovered by LAMOST using the Subaru Telescope. The hunt for evidence of massive stars, unique to the universe’s first stars, has been a longstanding challenge, a goal finally achieved by this study, says Professor AOKI Wako of NAOJ.
Determining what proportion of the initial stars were gargantuan is the next question astronomers must answer. To this end, the exploration and chemical analysis of many more stars is necessary. These groundbreaking results were published in the journal Nature.