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The complicated lives of stars

Figure 1: These diagnostic diagrams show stellar evolution simulations of massive and very massive stars (colourful labels in solar mass units). These are stellar lives in the Milky Way (left), in the Small Magellanic Cloud (middle) and in a metal-poor dwarf galaxy (right). One line on these diagrams belongs to one star’s whole life from birth to death. Their brightness is shown to change on the vertical axis, and their apparent ‘colour’ (surface temperature, with lower values meaning red and higher, blue) on the horizontal axis. These simulations can give a boost to research on how new stars are born and how old stars die.

Dorottya Szécsi

Our research team has developed new simulations of stars with various chemical compositions. These stellar evolution simulations can be used to predict how often gravitational-waves should be detected. Or, they can be applied to study the birth of new stars out of dense clouds. We call our simulations the BoOST project.

With stellar evolution simulations we can study almost any kind of stars. Not only those that we see, but also those that we cannot see. For example, stars that were born soon after the Big Bang used to have a different chemical composition than those stars that we see today. From our computer simulations, we can figure out what these early stars looked like: what was their colour, how bright they were and so on.

What's more, we can even predict what happens to them after they die. Some of them become black holes, for example, and we can tell the mass of this black hole based on how heavy the star had been before it exploded. This way it is possible to predict how often two black holes merge, and we hope that in the future this will give us statistics about how many times we can expect to detect gravitational-waves from various cosmic epochs.