Some ancient stars may have had some rather unusual deaths, according to a new study, possibly shedding some light on how today's Universe came to be.
Certain primordial stars - those between 55,000 and 56,000 times the mass of our Sun, or solar masses - would have exploded as supernovae and burned completely, leaving no remnant black hole behind. Seeing as how they are among the Universe's first generation of stars, they are especially interesting because they produced the first heavy elements (those other than helium and hydrogen).
In their spectacular deaths, they cast their chemical creations into outer space, paving the way for subsequent generations of stars, solar systems and galaxies. Scientists hope that by better understanding these explosions they can gain insight into the beginnings of the Universe.
"We found that there is a narrow window where supermassive stars could explode completely instead of becoming a supermassive black hole -- no one has ever found this mechanism before," lead author Ke-Jung Chen, a postdoctoral researcher at the University of California, Santa Cruz (UCSC), said in a statement.
The findings were published in the Astrophysical Journal.
Using a one-dimensional stellar evolution code called KEPLER, Chen and his colleagues were able to model the life of a primordial supermassive star. They found that primordial stars between 55,000 to 56,000 solar masses live about 1.69 million years before becoming unstable, at which point they start to collapse. As the star collapses, it begins to rapidly synthesize heavy elements like oxygen, neon, magnesium and silicon - with helium at its core - which creates so much energy that it results in a supernova explosion.
Depending on the intensity of the supernovae, some supermassive stars could, when they explode, enrich their entire host galaxy and even some nearby galaxies with elements ranging from carbon to silicon. In some cases, supernova may even trigger a burst of star formation in its host galaxy, which would make it visually distinct from other young galaxies.
According to the model CASTRO used by researchers, as these stars die, their instability mixes heavy elements produced in the star's final moments throughout the star itself. The research team says that this mixing should create a distinct observational signature that could be detected by upcoming near-infrared experiments such as the European Space Agency's Euclid and NASA's Wide-Field Infrared Survey Telescope.