Dying stars breathe life into Earth: study
As dying stars take their final few breaths of life, they gently sprinkle their ashes into the cosmos through the magnificent planetary nebulae. These ashes, spread via stellar winds, are enriched with many various chemical elements, including carbon.
Findings from a study published today in Nature Astronomy show that the ultimate breaths of those dying stars, called white dwarfs, shed light on carbon's origin within the Milky Way .
"The findings pose new, stringent constraints on how and when carbon was produced by stars of our galaxy, ending up within the staple from which the Sun and its planetary system were formed 4.6 billion years ago," says Jeffrey Cummings, an Associate Research Scientist within the Johns Hopkins University's Department of Physics & Astronomy and an author on the paper.
The origin of carbon, a component essential to life on Earth, within the Milky Way galaxy remains debated among astrophysicists: some are in favor of low-mass stars that blew off their carbon-rich envelopes by stellar winds became white dwarfs, et al. place the main site of carbon's synthesis within the winds of massive stars that eventually exploded as supernovae.
Using data from the Keck Observatory near the summit of Mauna Kea volcano in Hawaii collected between August and September 2018, the researchers analyzed white dwarfs belonging to the Milky Way's open star clusters. Open star clusters are groups of up to a couple of thousand stars held together by mutual gravity .
From this analysis, the research team measured the white dwarfs' masses, and using the idea of stellar evolution, also calculated their masses at birth.
The connection between the birth masses to the ultimate white dwarf star masses is named the initial-final mass relation, a fundamental diagnostic in astrophysics that contains the whole life cycles of stars. Previous research always found an increasing linear relationship: the more massive the star at birth, the more massive the white dwarf star left at its death.
But when Cummings and his colleagues calculated the initial-final mass relation, they were shocked to seek out that the white dwarfs from this group of open clusters had larger masses than astrophysicists previously believed. This discovery, they realized, broke the linear trend other studies always found. In other words, stars born roughly 1 billion years ago within the Milky Way didn't produce white dwarfs of about 0.60-0.65 solar masses, because it was commonly thought, but they died leaving more massive remnants of about 0.7—0.75 solar masses.
The researchers say that this kink within the trend explains how carbon from low-mass stars made its way into the Milky Way . within the last phases of their lives, stars twice as massive because the Milky Way's Sun produced new carbon atoms in their hot interiors, transported them to the surface and eventually spread them into the encompassing interstellar environment through gentle stellar winds. The research team's stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to permit the central cores of those stars, the longer term white dwarfs, to grow considerably in mass.
The team calculated that stars had to be a minimum of 1.5 solar masses to spread its carbon-rich ashes upon death.
The findings, consistent with Paola Marigo, a Professor of Physics and Astronomy at the University of Padova and therefore the study's first author, helps scientists understand the properties of galaxies within the universe. By combining the theories of cosmology and stellar evolution, the researchers expect that bright carbon-rich stars on the brink of their death, just like the progenitors of the white dwarfs analyzed during this study, are presently contributing to the sunshine emitted by very distant galaxies. This light, which carries the signature of newly produced carbon, is routinely collected by the massive telescopes from space and Earth to probe the evolution of cosmic structures. Therefore, this new understanding of how carbon is synthesized in stars also means having a more reliable interpreter of the sunshine from the far universe.
As dying stars take their final few breaths of life, they gently sprinkle their ashes into the cosmos through the magnificent planetary nebulae. These ashes, spread via stellar winds, are enriched with many various chemical elements, including carbon.
Findings from a study published today in Nature Astronomy show that the ultimate breaths of those dying stars, called white dwarfs, shed light on carbon's origin within the Milky Way .
"The findings pose new, stringent constraints on how and when carbon was produced by stars of our galaxy, ending up within the staple from which the Sun and its planetary system were formed 4.6 billion years ago," says Jeffrey Cummings, an Associate Research Scientist within the Johns Hopkins University's Department of Physics & Astronomy and an author on the paper.
The origin of carbon, a component essential to life on Earth, within the Milky Way galaxy remains debated among astrophysicists: some are in favor of low-mass stars that blew off their carbon-rich envelopes by stellar winds became white dwarfs, et al. place the main site of carbon's synthesis within the winds of massive stars that eventually exploded as supernovae.
Using data from the Keck Observatory near the summit of Mauna Kea volcano in Hawaii collected between August and September 2018, the researchers analyzed white dwarfs belonging to the Milky Way's open star clusters. Open star clusters are groups of up to a couple of thousand stars held together by mutual gravity .
From this analysis, the research team measured the white dwarfs' masses, and using the idea of stellar evolution, also calculated their masses at birth.
The connection between the birth masses to the ultimate white dwarf star masses is named the initial-final mass relation, a fundamental diagnostic in astrophysics that contains the whole life cycles of stars. Previous research always found an increasing linear relationship: the more massive the star at birth, the more massive the white dwarf star left at its death.
But when Cummings and his colleagues calculated the initial-final mass relation, they were shocked to seek out that the white dwarfs from this group of open clusters had larger masses than astrophysicists previously believed. This discovery, they realized, broke the linear trend other studies always found. In other words, stars born roughly 1 billion years ago within the Milky Way didn't produce white dwarfs of about 0.60-0.65 solar masses, because it was commonly thought, but they died leaving more massive remnants of about 0.7—0.75 solar masses.
The researchers say that this kink within the trend explains how carbon from low-mass stars made its way into the Milky Way . within the last phases of their lives, stars twice as massive because the Milky Way's Sun produced new carbon atoms in their hot interiors, transported them to the surface and eventually spread them into the encompassing interstellar environment through gentle stellar winds. The research team's stellar models indicate that the stripping of the carbon-rich outer mantle occurred slowly enough to permit the central cores of those stars, the longer term white dwarfs, to grow considerably in mass.
The team calculated that stars had to be a minimum of 1.5 solar masses to spread its carbon-rich ashes upon death.
The findings, consistent with Paola Marigo, a Professor of Physics and Astronomy at the University of Padova and therefore the study's first author, helps scientists understand the properties of galaxies within the universe. By combining the theories of cosmology and stellar evolution, the researchers expect that bright carbon-rich stars on the brink of their death, just like the progenitors of the white dwarfs analyzed during this study, are presently contributing to the sunshine emitted by very distant galaxies. This light, which carries the signature of newly produced carbon, is routinely collected by the massive telescopes from space and Earth to probe the evolution of cosmic structures. Therefore, this new understanding of how carbon is synthesized in stars also means having a more reliable interpreter of the sunshine from the far universe.
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