Stars as Laboratories for Fundamental Physics - MPP Theory Group

Preface
Ever since Newton proposed that the moon on its orbit follows the same
laws of motion as an apple falling from a tree, the heavens have been
a favorite laboratory to test the fundamental laws of physics, notably
classical mechanics and Newton’s and Einstein’s theories of gravity.
This tradition carries on—the 1993 physics Nobel prize was awarded
to R. A. Hulse and J. H. Taylor for their 1974 discovery of the binary
pulsar PSR 1913+16 whose measured orbital decay they later used to
identify gravitational wave emission. However, the scope of physical
laws necessary to understand the phenomena observed in the superlunar
sphere has expanded far beyond these traditional fields. Today,
astrophysics has become a vast playing ground for applications of the
laws of microscopic physics, in particular the properties of elementary
particles and their interactions.
This book is about how stars can be used as laboratories to probe
fundamental interactions. Apart from a few arguments relating to gravitational
physics and the nature of space and time (Is Newton’s constant
constant Do all relativistic particles move with the same limiting velocity
Are there novel long-range interactions), most of the discussion
focusses on the properties and nongravitational interactions of elementary
particles.
There are three predominant methods for the use of stars as particlephysics
laboratories. First, stars are natural sources for photons and
neutrinos which can be detected on Earth. Neutrinos are now routinely
measured from the Sun, and have been measured once from a collapsing
star (SN 1987A). Because these particles literally travel over astronomical
distances before reaching the detector one can study modifications
of the measured signal which can be attributed to propagation and dispersion
effects, including neutrino flavor oscillations or axion-photon
oscillations in intervening magnetic fields. It is well known that the
discrepancy between the calculated and measured solar neutrino spectra
is the most robust, yet preliminary current indication for neutrino
oscillations and thus for nonvanishing neutrino masses.
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