H II region

Definition

An H II region is a cloud of gas that has been ionized by ultraviolet light from nearby young, hot stars. These regions emit bright visible light, often appearing red due to the strong emission line of hydrogen.

5 Must Know Facts For Your Next Test

1. H II regions are primarily composed of hydrogen that has lost its electrons due to high-energy radiation.
2. They are often found in the spiral arms of galaxies where new star formation is actively occurring.
3. The size and brightness of an H II region depend on the number and type of ionizing stars within it.
4. They serve as indicators of recent star formation activity in galaxies.
5. The study of H II regions helps astronomers understand the process of star formation and the life cycle of stars.

Related terms

Nebula:

A general term for a cloud of gas or dust in space, which can be either dark or glowing depending on its contents and energy sources.

Emission Line:

A bright line in a spectrum caused by the emission of photons from atoms, typically seen in glowing gas clouds like H II regions.

Star Formation:

The process by which dense regions within molecular clouds collapse to form stars, often traced by observing H II regions.