An emission nebula is a nebula formed of ionized gases that emit light of various colors. The most common source of ionization is high energy photons emitted from a nearby hot star. Among the several different types of emission nebulae are H II regions, in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae, in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.
Usually, a young star will ionize part of the same cloud from which it was born although only massive, hot stars can release sufficient energy to ionize a significant part of a cloud. In many emission nebulae, an entire cluster of young stars is doing the work.The nebula’s color depends on its chemical composition and degree of ionization. Due to the prevalence of hydrogen in interstellar gas, and its relatively low energy of ionization, many emission nebulae appear red due to the strong emissions of the Balmer series.
Climb the mountains and get their good tidings. Nature’s peace will flow into you as sunshine flows into trees. The winds will blow their own freshness into you, and the storms their energy, while cares will drop off like autumn leaves. — John MuirDefinitions of the Pacific Northwest region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common conception of the Pacific Northwest includes the U.S. states of Oregon and Washington as well as the Canadian province of British Columbia. This definition is often restricted further to include only the coastal areas west of the crest of the Cascade Mountains and Canadian Coast Mountains. A key aspect of the Pacific Northwest is the US- Canada international border, which the United States and United Kingdom established at a time when the region’s inhabitants were composed mostly of Indigenous peoples. The border in two sections, along the 49th parallel south of British Columbia and the Alaska Panhandle west of northern British Columbia has had a powerful effect on the region. According to Canadian historian Ken Coates, the border has not merely influenced the Pacific. Definitions of the Pacific Northwest region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common conception of the Pacific Northwest includes the U.S. states of Oregon and Washington as well as the Canadian province of British Columbia.
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