This ultraviolet-light data from the Hubble Space Telescope's Cosmic Origins Spectrograph shows strong helium II absorption and transmission lines from a quasar, identifying an era 11.7 to 11.3 billion years ago when electrons were stripped from primeval helium atoms — a process called reionization.
Object Names: HE 2347-4342, QSO B2347-4342
Image Type: Astronomical/Illustration
Credit: Shull et al., ApJ, 722: 1312-1324, October 20, 2010
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