A cloudlike region in space where the interstellar medium consists of ionized rather than neutral hydrogen. HII regions are centered around stars with very high surface temperatures and brilliant luminosities, whose radiant energy is sufficient to heat the interstellar medium to the point that hydrogen is ionized. The most conspicuous and best-known HII region is the Orion Nebula.
health information infrastructure
[hee-oo-mah] /ˈhi uˌmɑ/ noun 1. an island in the Baltic, W of and belonging to Estonia. 373 sq. mi. (965 sq. km).
[hi-jahb, -jab] /hɪˈdʒɑb, -ˈdʒæb/ noun 1. a traditional scarf worn by Muslim women to cover the hair and neck and sometimes the face. 2. the traditional dress code of Muslim women, calling for the covering of the entire body except the face, hands, and feet: to observe the hijab. /hɪˈdʒæb; hɛˈdʒɑːb/ noun 1. a covering […]
[hahy-jak-er] /ˈhaɪˌdʒæk ər/ noun 1. a person who .