All stars are natural magnets, thanks to the dynamic, electrically conductive gases that compose them. And because the magnetic fields of stars can be very strong, they represent a basic physical ingredient in the theory of stellar structure and evolution. In recently years it has been clearly demonstrated that magnetic fields have essential impacts on stellar lives, modifying their interior fluid flows, changing their internal rotational profiles and distributions of nucleosynthetic chemicals, channeling and modifying their outflowing winds, and slowing their surface rotation through "magnetic braking".
Ultimately, these effects result in important changes to the evolution of stars, leading in particular to significant modifications of the relationships between stellar temperatures, luminosities, sizes and ages. They also influence the important outputs of stars in terms of the mass and luminous energy injected into the surrounding interstellar medium during their lives. More remarkably, they can also influence the dramatic supernova explosions that mark the deaths of the most massive stars. These effects directly impact the properties of exotic remnant white dwarf and neutron stars, and affect how populations of stars contribute to the structure and chemistry of their local galactic environments.
As stars age and evolve, so too do their magnetic fields. Hence we expect to observe important transformations of stellar magnetic fields as stars pass through various cycles of nuclear burning and undergo large changes to their temperatures, luminosities and sizes.
As a consequence, the magnetic field of a star at one stage of its life may appear very different from that at a later stage. This prompts fundamental questions such as: Can the magnetic field of a star from an earlier evolutionary stage "seed" the production of a very different magnetic field in that star at a later stage? Do magnetic fields with similar characteristics in stars at very different evolutionary phases have any relationship to one another?
In this talk I will describe results of our ongoing systematic exploration of the characteristics of magnetic fields of stars of various types, with two principal
applications: understanding quantitatively how magnetic fields influence stellar structure and evolution, and investigating how the observable magnetic fields of stars transform over stellar evolutionary timescales.
Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto