Data challenge

The Hubble tension — the ~5σ disagreement between early- and late-universe measurements of H0 — remains one of the most pressing open problems in cosmology. A key question is how much of the scatter in local H0 measurements is driven by methodological choices in the TRGB (Tip of the Red Giant Branch) distance ladder. This challenge is designed to quantify exactly that.

We are providing participants the tools needed to analyze the data used to measure H0. We are asking participants to independently measure TRGB distances to a set of supernova host galaxies using a common and public photometric dataset, then feed those distances into a fixed supernova pipeline to obtain H0. By comparing results across participants, we can isolate the effect of TRGB methodology from all other sources of scatter. The Data Challenge materials assume no prior knowledge of the field, and so participants will be able to learn how to use these tools through the notebooks and accompanying lecture videos from the CosmoVerse school held in Sofia, Bulgaria, which will be available on the CosmoVerseSchool@Sofia page.

Main coordinator: Siyang Li

Coordinators: Siyang Li, Eleonora Di Valentino, and Jackson Said