and collapse. Advances in laboratory astrophysics lead to a better understanding of the underlying nuclear, atomic, and magnetohydrodynamic (MHD) processes. New technology for optical and infrared (IR) spectropolarimetry and for interferometry open up the possibility of seeing magnetic fields and resolving the disks of stars. When well-sampled imaging is coupled to powerful systems for processing vast quantities of data sampled over time, subtle features of stellar interiors can be inferred. Similarly, rare and rapid transients that have eluded surveys to date will surely be found, and may be connected with gravitational waves.

These advances are certain to open up a new and unexplored world of investigation on timescales from seconds to decades. In this report, the Astro2010 Science Frontiers Panel on Stars and Stellar Evolution sketches the most fertile opportunities for the coming decade in the field of stars and stellar evolution. The panel is confident that it will prove a fruitful decade for this field of astronomy, with the resolution of today’s questions producing many new problems and possibilities.

As requested by the Astro2010 committee, the panel formulated its report around four science questions and one outstanding discovery opportunity. The panel is under no illusion that this short list is complete: the field is so rich that there will surely be advances in areas not emphasized here. The panel does, however, have every reason to believe that these questions capture some of the most promising areas for advances in the coming decade. The four questions and discovery opportunity are as follows:

  1. How do rotation and magnetic fields affect stars?

  2. What are the progenitors of Type Ia supernovae and how do they explode?

  3. How do the lives of massive stars end?

  4. What controls the mass, radius, and spin of compact stellar remnants?

  5. Unusual discovery potential: time-domain astronomy—in which the technology on the horizon is well matched to the many timescales of stellar phenomena.

The subsections below summarize the main points.

How Do Rotation and Magnetic Fields Affect Stars?

There’s an old chestnut about a dozing theorist at the weekly colloquium who opens his eyes at the end of every talk and rouses himself to ask, to great approbation for his subliminal understanding, “Yes, all very interesting, but what about rotation and magnetic fields?”

Astronomers are now in a position to address this question in a serious way. In the Sun, the effects are visible; in many other stars they are likely to be much more important. It is not sufficient to think of rotation and magnetism as perturbations on a one-dimensional star. These are fundamental physical phenomena that demand a three-dimensional representation in stars.



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