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Updated: May 26, 2026

Measurement and Analysis of Atomic Hydrogen and Diatomic Molecular AlO, C2, CN, and TiO Spectra Following Laser-induced Optical Breakdown
Published on: February 14, 2014
Voyager measurements of hydrogen Lyman-α diffuse emission from the Milky Way
Rosine Lallement1, Eric Quémerais, Jean-Loup Bertaux
1Galaxies, Etoiles, Physique, Instrumentation (GEPI), Observatoire de Paris, CNRS, Université Paris Diderot, Place Jules Janssen, Meudon, France. rosine.lallement@obspm.fr
Abstract:
Doppler-shifted hydrogen Lyman-alpha (Lyα) emission from galaxies is currently measured and used in cosmology as an indicator of star formation. Until now, the Milky Way emission has not been detected, owing to far brighter local sources, including the H (hydrogen) glow, i.e., solar Lyα radiation backscattered by interstellar atoms that flow within the solar system. Because observations from the Voyager spacecraft, now leaving the heliosphere, are decreasingly affected by the H glow, the ultraviolet spectrographs are detecting Lyα diffuse emission from our Galaxy. The surface brightness toward nearby star-forming regions is about 3 to 4 rayleighs. The escape fraction of the radiation from the brightest H II regions is on the order of 3% and is highly spatially variable. These results will help in constraining models of Lyα radiation transfer in distant galaxies.
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