H I region
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This article was last edited by Aeusoes1 (talk | contribs) 19 years ago. (Update timer) |
An H I region is an interstellar cloud composed of neutral atomic hydrogen (H1). These regions are non-luminous but are detectable because molecules present in small quantities emit radiation in the 21-cm (1,420 MHz) region of the radio-spectrum, even at low temperatures. At ionization fronts, where HI regions collide with expanding ionized gas (such as an H II region, the latter glows brighter than it otherwise would.
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