The second Gaia data release (DR2, spring 2018) included a unique all-sky catalogue of large-amplitude long-period variables (LPVs), that include Miras and semi-regular variables. These stars are on the Asymptotic Giant Branch (AGB), and are characterized by high luminosity, changing surface composition, and intense mass loss that make them of paramount importance for stellar, galactic, and extra-galactic studies. An initial investigation of these data for LPVs in the Large Magellanic Cloud (LMC) has revealed the possibility to disentangle O-rich and C-rich stars using a combination of optical Gaia and infrared 2MASS photometry. The so-called Gaia-2MASS diagram constructed to achieve this has further been shown to enable the identification of sub-groups of AGB stars among the O-rich and C-rich LPVs. Here, we extend this initial study of the Gaia-2MASS diagram to the Small Magellanic Cloud (SMC) and the Galaxy, and show that the remarkable properties found in the LMC also apply to these other stellar systems. Interesting features, moreover, emerge as a result of the different metallicities between the three stellar environments, which we highlight in this exploratory presentation of Gaia’s potential to study stellar populations harboring LPVs. Finally, we look ahead to the future and highlight the power of the exploitation of Gaia RP spectra for the identification of carbon stars using solely Gaia data in forthcoming data releases. These proceedings include three animated images that can be used as outreach materials.

Figs.12-14 updated; animated images and movies added; small updates