4 ms·

Error analysis of cosmic distance ladder is fiercely technical subject. https://arxiv.org/abs/1103.2976 https://arxiv.org/abs/1103.2976 Table 5 is titled "H0 Er

Error analysis of cosmic distance ladder is fiercely technical subject. https://arxiv.org/abs/1103.2976 https://arxiv.org/abs/1103.2976 Table 5 is titled "H0 Error Budget for Cepheid and SN Ia Distance Ladders". (It is old and the field is moving fast, but this is what I happened to remember.) Among total error of 3.1%, Cepheid reddening is 1.4% and the second largest source of uncertainty. SN Ia statistics is the largest with 1.9%. Rarely discussed in popular treatment is anchor distance, the third largest source with 1.3%. It is uncertainty of bottom lungs of the ladder, eg the distance to Large Magellanic Cloud before Cepheid and SN Ia are involved.

raattgift 3y ago
> Rarely discussed in popular treatment is anchor distance Yes, and I'm sad that it's so rare. The Megamaser Cosmology Project is incredibly awesome; combining line of sight acceleration, velocity, velocity gradient, and observer angle on the sky is very "anchor". https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyProject https://safe.nrao.edu/wiki/bin/view/Main/MegamaserCosmologyP... Gaia seems to be making good progress on direct parallax up to kiloparsecs. And always happy to plug ASAS-SN <https://www.astronomy.ohio-state.edu/asassn/index.shtml https://www.astronomy.ohio-state.edu/asassn/index.shtml> (The deleted @SuperASASSN was one of the best astro follows on twitter some years ago), who have found an awful lot of detached eclipsing binaries: <https://academic.oup.com/mnras/article/517/2/2190/6695108?login=false https://academic.oup.com/mnras/article/517/2/2190/6695108?lo...>.