Extended Data Fig. 8: Stellar evolution tracks versus time.

Here we show the total magnification required to lens stars to Earendel’s apparent magnitude as a function of time on stellar evolution tracks (BoOST 0.1Z_⊙, as plotted in the H–R diagram Fig. 3). This required magnification changes over the lifetime of each star as it varies in luminosity or temperature, changing the flux observed in the F110W filter. We find that stars at ~100M_⊙ and above spend the most time (~2 Myr) in the green region that reproduces Earendel’s observed flux, given our magnification estimates. But considering that lower-mass stars are more numerous, we conclude that masses of roughly (50–100)M_⊙ are most likely if Earendel is a single star.