What is H I region?
An '''HI region''' or '''H I''' region (''H one'') is a [[interstellar cloud|cloud]] in the [[interstellar medium]] composed of neutral atomic [[hydrogen]] (HI). These regions do not emit detectable [[visible light]] (except in [[spectrum|spectral lines]] from [[metal]] [[element]]s). H I regions are clouds of neutral hydrogen which glow faintly with [[infrared]] light. Because they are common in our galaxy, they obscure distant views at extreme [[ultraviolet]] and soft [[x-ray]] [[wavelengths]]. An exception is the [[Lockman Hole]], through which we have a fairly clear window to distant objects. Another window into [[outer space|deep space]] is the [[Chandra Deep Field South]]. This was chosen for the [[Chandra X-ray Observatory]] [[artificial satellite|satellite]]. [[Category:Milky Way]] [[Category:Hydrogen]] {{sci-stub}}