Massive stars meet a dramatic end in a supernova spectacle, radiating brilliance brighter than entire galaxies as they expel stellar material into space while their cores transform black holes or neutron stars. Scientists, after observing and analyzing numerous such explosions, have identified an intriguing trend.
A substantial portion of supernovas lacks hydrogen, indicating the existence of a noteworthy population of hydrogen-poor stars as their origin, aligning with earlier predictions by astronomers estimating that approximately one-third of massive supernova progenitors are hydrogen-deficient.
Scientists Solve Hydrogen-Poor Supernova Mystery
After years of uncertainty, scientists can finally lay to rest the mystery surrounding the absence of hydrogen in a significant number of supernovas.
Conducting a specialized survey to pinpoint these elusive stars, researchers, including astronomer Maria Drout from the University of Toronto and astrophysicist Ylva Götberg from the Institute of Science and Technology Austria, discovered 25 stars that perfectly fit the anticipated profile.
This groundbreaking revelation not only confirms the existence of the hypothesized hydrogen-poor stars but also provides a clear method for their identification.
Drout emphasized the magnitude of this discovery, describing the previous lack of information on these stars as a "big, glaring hole." The potential rarity of these stars has raised questions about the accuracy of the theoretical framework governing various astrophysical phenomena, such as supernovae, gravitational waves, and the illumination of distant galaxies.
The newfound evidence not only establishes the reality of these hydrogen-poor stars but also underscores the importance of refining our understanding of celestial events.
Researchers reported their findings in full in the study, titled "The drivers of massive star evolution" published in Science, after successfully identifying the elusive precursor stars through a combination of theoretical modeling and observational techniques. This first-of-its-kind star population was located in the nearby Large Magellanic Cloud and the Small Magellanic Cloud.
Intriguingly, these stars exhibited a bluish hue, contrary to the typical reddening observed in single stars as they age. The resolution of this decades-old enigma not only enriches our knowledge of stellar evolution but also has far-reaching implications for advancing our comprehension of the broader cosmic landscape.
Hydrogen-Poor Supernovas Came From Binary Stars
According to existing theories, stripped-envelope supernovas, also known as hydrogen-poor supernovas, originate from binary star systems. In these systems, one star pulls material from its binary companion, resulting in a helium-rich star with minimal hydrogen content.
This process leads to a scenario where the exploding star releases limited hydrogen when it reaches the end of its life cycle. While high-mass helium stars at the upper end of the stellar mass range have been observed, the mid-range stars between 8 and 25 times the mass of the Sun, crucial for the formation of neutron stars and neutron star mergers, have been scarce.
The challenge lies in detecting mid-range stars crucial to the formation of neutron stars, given their depletion of outer layers and the presence of a brighter companion in close orbit. Researchers addressed this by using ultraviolet light in surveys from 2018 to 2022, employing the Swift Ultra-Violet/Optical Telescope to study millions of stars in the Magellanic Clouds.
The team's groundbreaking discovery of stripped helium stars represents a crucial first step, and ongoing efforts, including in-depth studies and expanded searches, underscore the need for collaboration and the development of new methods to identify these intermediate-mass stars that have potentially been overlooked.
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