 |
|
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
| • HOME • ABOUT • CATEGORIES • USE OF TEXT AND IMAGES • NEWSLETTER   
|
HI region
An interstellar cloud composed primarily of atomic hydrogen, detectable by its radio wave emission in the 21-centimeter line. HI regions have a density of 1 to 10 atoms/cm3 and a temperature of about 125 K (the spin temperature of neutral hydrogen). At least 95% of interstellar hydrogen is HI.
Related category
• INTERSTELLAR AND INTERPLANETARY MATTERAlso on this site:
Encyclopedia of Alternative Energy & Sustainable Living
Encyclopedia of History