Detection of intergalactic ionized helium absorption in a high-redshift quasar

Observations obtained with the recently refurbished Hubble Space Telescope reveal strong absorption arising from singly ionized helium along the line of sight to a high-redshift quasar. The strength of the absorption suggests that it may arise in a diffuse ionized intergalactic medium. The detection also confirms that substantial amounts of helium existed in the early Universe, as predicted by Big Bang nucleosynthesis theory.