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https://phys.org/news/2023-01-astronomers-super-hot-stars.htmlAn international team of astronomers has discovered eight of the hottest stars in the universe, all with surfaces hotter than 100,000 degrees Celsius. The work was published in Monthly Notices of the Royal Astronomical Society.
The paper is based on data gathered using the Southern African Large Telescope (SALT), the largest single optical telescope in the southern hemisphere, with a 10m x 11m mirror. The study describes how a survey of helium-rich subdwarf stars led to the discovery of several very hot white dwarf and pre-white dwarf stars, the hottest of which has a surface temperature of 180,000 degrees Celsius. For comparison, the sun's surface is a mere 5,800 degrees.
One of the stars identified is the central star of a newly discovered planetary nebula, which is one light year in diameter. Two of the others are pulsating, or "variable" stars. All of these stars are at an advanced stage of their life cycle and are approaching the end of their lives as white dwarfs. Due to their extremely high temperatures, each of these new discoveries is more than one hundred times brighter than the sun, which is considered unusual for white dwarf stars.
Hot white dwarfs are the remnants of stars that have exhausted their nuclear fuel and shed their outer layers, leaving behind a dense, hot core. Pre-white dwarfs are stars in the transitional phase between the end of their main sequence life and becoming a white dwarf. They are still cooling and contracting before they settle into the white dwarf phase.
SALT stands for the Southern African Large Telescope, which is one of the largest optical telescopes in the world. It contributes to discovering white dwarfs by providing high-resolution spectroscopic data that allows scientists to analyze the light from these stars, determine their composition, temperature, and other physical properties.
The discoveries of hot white dwarfs and pre-white dwarfs are significant because they provide insights into the late stages of stellar evolution. Studying these objects helps scientists understand the processes that stars undergo as they die, the chemical enrichment of the galaxy, and the future of our own Sun.
To identify hot white dwarfs and pre-white dwarfs, astronomers use a combination of photometric surveys, which measure the brightness of stars in different wavelengths, and spectroscopic observations, which analyze the light spectrum emitted by the stars. These methods help determine the temperature, surface gravity, and chemical composition of the stars.
Future research directions include detailed follow-up observations to refine the physical parameters of these stars, studying their atmospheres and compositions in more detail, and using theoretical models to better understand their evolution. Additionally, researchers aim to discover more such objects to build a comprehensive picture of the population of hot white dwarfs and pre-white dwarfs in our galaxy.