i know its measured in lightyears but im watching a video on the james webb telescope and the discovery of huge galaxies and how we have to rethink the beginning but how do they know how old the galaxies are by just pictures? i imagine they have a lot of other things that tell them more information but still. it seems damn near impossible to even tell what anything is especially with how small and warped it is too. thank you i appreciate any info on this. im just throwing the math flair since theres no space
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A bunch of different ways: Cepheids as koolaid said,
Parallax can be used to measure objects in our galaxy just be measuring angles at different places in Earth’s orbit.
Type I supernovae, supernova from binary stars where a white dwarf is siphoning matter from another star, always explode at 1.44 solar masses. Which means their luminosity is constant and changes in perceived luminosity becomes a range-finder.
The last is red-shift. We see a fairly predictable relationship between relative velocity (which causes redshift) and distance, so if we see how much a hydrogen line is red-shifted we can estimate the distance.
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