Galaxies2026-07-302 minarXiv:2607.27860expressBright Quasars Hide Magnesium Lines — It's All About Gas DensityA bright lantern in thick fog seems dim, while a weak flame in clear air can be seen a kilometer away. A similar oddity baffled astrophysicists almost half a century ago.Wen-Qiang Liang·Zhi-Fu Chen·Rui-Jing Lu·Cheng-Feng Peng·Shao-Hua Zhang·Zhe-Geng Chen·Zhi-Qing Chen·Yi-Qi Chen·Dong-Li Jiang·Xi-Heng Shi·Zhi-Wen WangCompton effectArthur ComptonAlbert EinsteinArno PenziasquasarAccretion diskactive galactic nucleusspectroscopy👍👎☆SimplePopularAdvanced