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By using yet another kind of standard candle—stars called red giants that, on the verge of extinction, undergo a “helium flash” that reliably indicates their luminosity—Freedman and her colleagues had arrived at a value that, as their paper said, “sits midway in the range defined by the current Hubble tension”: 69.8 ± 0.8—a result that offers no reassuring margin-of-error overlap with that from either SH0ES or Planck.

This process culminates in a “helium flash,” a rapid brightening due to a surge in helium burning, after which a star dramatically dims.

Astrophysical models can accurately predict the highest temperatures and pressures at which a helium flash takes place, allowing researchers to discern the peak brightness a red giant can reach.