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Which chemical elements besides hydrogen are found in H II regions?
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H II region
Centre of the Orion Nebula (M42). Astronomers have identified some 700 young stars in this 2.5-light-year-wide area. They have also detected over 150 protoplanetary disks, or proplyds, which are believed to be embryonic solar systems that will eventually form planets. These stars and proplyds generate most of the nebula's light. This picture is a mosaic combining 45 images taken by the Hubble Space Telescope.
In addition to hydrogen, H II regions contain several other chemical elements. While hydrogen is the primary component, helium is the second most abundant element, typically found at about 0.1 times the abundance of hydrogen by the number of atoms.12
Other significant elements present in these regions include:
- Carbon12
- Nitrogen12
- Oxygen12
- Neon1
- Sulfur1
- Argon1
The abundances of these elements are determined by analyzing nebular spectra, specifically by measuring emission lines produced by various stages of ionization. While these elements are present in measurable quantities, their exact abundance estimates can vary depending on whether researchers use collisionally excited lines or recombination lines for their calculations, a discrepancy that remains a subject of scientific study.1