Hβ emission line at the rest frame λ = 4861 Å wavelength. This ratio is well defined through models and observational studies, but caution should be taken, as the ratio is often degenerate, providing both a low and high metallicity solution, which can be broken with additional line measurements. Similarly, other strong forbidden line ratios can be used, e.g. for sulfur, where Metal abundances within HII regions are typically less than 1%, with the percentage decreasing on average with distance from the Galactic Center. Galaxies In November 2022, astronomers, using the Hubble Space Telescope, discovered one of the most metal-poor galaxies known. This nearby dwarf galaxy, 20 million ly away and 1,200 ly across, is named HIPASS J1131–31 (nicknamed the "Peekaboo" Galaxy). According to one of the astronomers, "Due to Peekaboo’s proximity to us, we can conduct detailed observations, opening up possibilities of seeing an environment resembling the early universe in unprecedented detail." See also References Further reading Page 593-In Quest of the Universe Fourth Edition Karl F. Kuhn Theo Koupelis. Jones and Bartlett Publishers Canada. 2004. Astrophysics Physical cosmology Stellar astronomy Concepts in astronomy