Axion dark matter and solar halos

Axions are new light particles introduced to explain the apparent absence of time-reversal symmetry violations in nuclear interactions. If they exist, they also automatically comprise a component or all of the dark matter of our Universe. Although their dynamics is governed by simple equations, these give rise to a plethora of fascinating phenomena, some of which have crucial consequences for experimental searches and for the evolution of our Universe. After introducing the basics of axion physics and the status of experimental searches, I will discuss recent developments in the understanding of the cosmological axion dark matter abundance and show that these particles can form dense halos around astrophysical objects, for instance the Sun.