Using Mira Variables for Cosmological Distance Measurements

The present-day expansion rate of the universe, known as the Hubble Constant, is one of the only directly measurable cosmological parameters. In recent years, the persistent disagreement between the value of the Hubble Constant obtained from direct distance-ladder measurements to nearby galaxies and the value inferred from observations of the CMB and assuming a standard Lambda-CDM cosmological model has become one of the strongest indications of new physics. While the most precise distance ladder currently uses Cepheids, independent measurements of distances made with other standard candles can serve as a cross-check of systematics in distance measurements, allowing us to solidify or resolve the tension. One such alternative precision distance indicator and calibrator of Type Ia SNe are Mira variables – highly-evolved, asymptotic giant branch stars – which are astrophysically distinct from the more commonly-used Cepheids or Tip of the Red Giant Branch (TRGB). In addition to being highly luminous and ubiquitous, Miras are capable of being detected and characterized using only near-infrared and infrared observations, which is particularly advantageous in the era of JWST and Roman. In my talk, I will discuss current progress in the development of the Mira distance ladder and its Hubble Constant measurements with a focus on recent HST and JWST observations of Mira variables in M101, the nearest recent host galaxy of a Type Ia supernova.