What is HYDROGEN I, II?

The hydrogen of interstellar space, known in two clearly defined states: HI neutral hydrogen and HII ionized hydrogen. The HI regions, confined mainly to the spiral arms of the galaxy, emit no visible light, and are detected solely by their emission of the 21- cm radio line. The HII regions, found in the gaseous nebulae, emit both visible light and radio waves.


Link to This Definition

Did you find this definition of HYDROGEN I, II helpful? You can share it by copying the code below and adding it to your blog or web page.
Edited and fact checked by Pam: Google +