asteroseismology tagged posts

Why stars spin down, or up, before they die

Why stars spin down, or up, before they die
Illustration of the inner regions of a massive star during its final oxygen (green) and silicon (teal) shell burning phase, before the collapse of the iron core (indigo). The strength and geometry of the magnetic field, combined with the properties of convection in the oxygen region can cause the rotation rate to speed up or slow down. Credit KyotoU / Lucy McNeill

From birth to death, stars generally slow by 100 to 1,000 times their initial rotation rates; in other words, they “spin down.” The sun’s total angular momentum has declined as material is gradually blown off at the surface as solar wind. By observing this, astronomers have theorized the interaction between magneticfields and plasma flow to be the most efficient way to spin down stars.

Why and how this happens has long int...

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Dating the Stars – Scientist provide most Accurate Picture yet

Milky Way_720
Credit: NASA

Scientists have succeeded in dating some of the oldest stars in the galaxy with unprecedented precision by combining data from the stars’ oscillations with information about their chemical composition.

The team, led by researchers at the University of Birmingham, surveyed around 100 red giant stars, and were able to determine that some of these were originally part of a satellite galaxy called Gaia-Enceladus, which collided with the Milky Way early in its history.

The results, published in Nature Astronomy, revealed that the group of stars surveyed all have similar ages, or are slightly younger than the majority of the stars known to have started their lives within the Milky Way...

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Mixing Massive Stars

A diagram of the internal mixing of a massive star
A simulation of a 3-solar-mass star shows the central, convective core and the waves it generates in the rest of the star’s interior.
Photo Credit:  PHILIPP EDELMANN

New research reveals hidden processes at work in the hearts of large stars. Astronomers commonly refer to massive stars as the chemical factories of the Universe. They generally end their lives in spectacular supernovae, events that forge many of the elements on the periodic table. How elemental nuclei mix within these enormous stars has a major impact on our understanding of their evolution prior to their explosion. It also represents the largest uncertainty for scientists studying their structure and evolution.

A team of astronomers led by May Gade Pedersen, a postdoctoral scholar at UC Santa Barbara’s Kavli Institut...

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The Science of Spin: Asteroseismologists confirm older stars rotate faster than expected

Astroseismology_720
Credit: Mark Garlick/University of Birmingham

Stars spin faster than expected as they age according to a new study led by scientists at the University of Birmingham which uses asteroseismology to shed new light on this emerging theory.

All stars, like the Sun, are born spinning. As they grow older, their spin slows down due to magnetic winds in a process called ‘magnetic braking’. Research published in 2016 by scientists at Carnegie Observatories delivered the first hints that stars at a similar stage of life as the Sun were spinning faster than magnetic braking theories predicted. The results from this study were based on a method in which scientists pinpoint dark spots on the surface of stars and track them as they move with the stars’ spin...

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