  Axions are a natural consequence of the Peccei-Quinn mechanism, the most
compelling solution to the strong-CP problem. Similar axion-like particles
(ALPs) also appear in a number of possible extensions of the Standard Model,
notably in string theories. Both, axions and ALPs, are very well motivated
candidates for Dark Matter (DM), and they would be copiously produced at the
suns core. A relevant effort during the last two decades has been the CAST
experiment at CERN, the most sensitive axion helioscope to date. The
International Axion Observatory (IAXO) is a large-scale 4th generation
helioscope, and its primary physics goal is to extend further the search for
solar axions or ALPs with a final signal to background ratio of about 5 orders
of magnitude higher.
  We briefly review here the astrophysical hints and models that will be at
reach while searching for solar axions within the context of the IAXO
helioscope search program, and in particular the physics under reach for
BabyIAXO, an intermediate helioscope stage towards the full IAXO.
