Deep-Sky Object
H I Region
A cloud of neutral hydrogen, glowing at 21 cm.
Cold, neutral atomic hydrogen detected by its 21 cm radio line — the dominant component of the interstellar medium by mass.
Overview
Cold, neutral atomic hydrogen detected by its 21 cm radio line — the dominant component of the interstellar medium by mass.
See also
Emission Nebula
A glowing cloud of ionised gas.
Cometary Globule
A dark cloud with a glowing tail.
Orion Nebula (M42)
A stellar nursery glowing in Orion's sword.
Dark Nebula
A cold cloud blocking the stars behind it.
Diffuse Nebula
Interstellar cloud of gas and dust visible by emission, reflection, or absorption.
Giant H II Region
Interstellar cloud of gas and dust visible by emission, reflection, or absorption.