Lockman Hole
The Lockman Hole is an area of the sky in which minimal amounts of neutral hydrogen gas are observed. Clouds of neutral hydrogen glow faintly with infrared light and obscure distant views at extreme ultraviolet and soft x-ray wavelengths. They interfere with observations at those wavelengths in nearly all other directions since they are common in our galaxy. So the Lockman Hole serves as a relatively clear window on distant objects, which makes it an attractive area of the sky for observational astronomy surveys. It is located near the pointer stars of the Big Dipper in the constellation Ursa Major and is about 15 square degrees in size. It is named after its discoverer, astronomer Felix Lockman.
The Lockman Hole is located at about RA 10h 45m, Dec. +58° and is defined by a region of low neutral hydrogen gas and dust column density. Column density is a commonly used measure in astronomy for the quantity of a given chemical element or molecule in a certain direction. In this region, the typical column density of neutral hydrogen is NH = 0.6 x 1020 cm−2. This column density is moderately lower than typical values near the galactic poles, where NH 1020 cm−2, and H I column densities of NH > 1021 cm−2 are common at low galactic latitudes and towards H I clouds.
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