hydrogen line

(redirected from 21-centimeter radiation)
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hydrogen line

(21 cm line) See H I region.

hydrogen line

[′hī·drə·jən ‚līn]
(spectroscopy)
A spectral line emitted by neutral hydrogen having a frequency of 1420 megahertz and a wavelength of 21 centimeters; radiation from this line is used in radio astronomy to study the amount and velocity of hydrogen in the Galaxy.
References in periodicals archive ?
By using 21-centimeter radiation to pinpoint if and when holes formed and merged, low-frequency radio telescopes such as LOFAR, a set of radio dishes spread across the Netherlands and other parts of Europe, will map out the history of the first stars, says Avi Loeb of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.