| 单词 | extragalactic h ii region |
| 释义 | extragalactic H II regionextragalactic H II region(eks-tră-gă-lak -tik) A cloud of hot ionized gas that is isolated in extragalactic space and is believed to consist of intergalactic gas that has begun to condense into stars and will probably become a dwarf irregular galaxy. Extragalactic H II regions were identified in 1970. They have no old stars, and a low metallicity indicates that some (like the compact galaxy IZw18) are less than 108 years old. These are the only ‘galaxies' significantly different in age from our Galaxy. |
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