IN 1896 Prof. E. C. Pickering discovered a series of lines in the spectrum of the star ζ Puppis which has been attributed to hydrogen in consequence of numerical relationship to the Balmer series ...

Astronomers have now observed the radio emission from the neutral hydrogen gas (HI) in a nearby galaxy. Hydrogen gas emits radio emission in a spectral line at a very specific frequency of 1420 MHz.

IN a letter to NATURE of February 11, Prof. J. W. Nicholson discusses the recent interesting experiments of Mr. Evans on the spectrum emitted from a vacuum tube containing highly purified helium and ...