when was it first observed?
1610
H II region
The French observer Nicolas-Claude Fabri de Peiresc is credited with the discovery of the Orion Nebula in 1610.
what is h ii region? A region of interstellar atomic hydrogen that is ionized. where is it located? The Orion Nebula, the Eta Carinae Nebula, and the Berkeley 59 / Cepheus OB4 Complex. how far is it from earth? Sometimes several hundred light-years across.
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H II region [SEP] Observations
A few of the brightest H II regions are visible to the naked eye. However, none seem to have been noticed before the advent of the telescope in the early 17th century. Even Galileo did not notice the Orion Nebula when he first observed the star cluster within it (previously cataloged as a single star, θ Orionis, by Johann Bayer). The French observer Nicolas-Claude Fabri de Peiresc is credited with the discovery of the Orion Nebula in 1610. Since that early observation large numbers of H II regions have been discovered in the Milky Way and other galaxies. William Herschel observed the Orion Nebula in 1774, and described it later as "an unformed fiery mist, the chaotic material of future suns".