Este fue
tu cielo.

A Sky Full Of Hydrogen

Interstellar space is filled with extremely tenuous clouds of gas, mostly hydrogen. A neutral hydrogen atom, or HI in astronomer's shorthand, consists of one proton and one electron. When the proton and electron switch from a parallel to an anti-parallel spin configuration, they emit radio waves with a wavelength of 21 centimeters. This rare event allows astronomers to map the distribution of hydrogen throughout the galaxy.