A galaxy is a massive ensemble of hundreds of millions of stars, all gravitationally interacting, and orbiting about a common center. Astronomers estimate that there are about 125 billion galaxies in the universe. All the stars visible to the unaided eye from Earth belong to Earth’s galaxy, the Milky Way. The Sun, with its associated planets, is just one star in this galaxy. Besides stars and planets, galaxies contain clusters of stars; atomic hydrogen gas; molecular hydrogen; complex molecules composed of hydrogen, nitrogen, carbon, and silicon, among others; and cosmic rays, which are collectively called interstellar matters.
- galaxy [ˈɡæləksi] n.星系
- massive [ˈmæsiv] adj. 大量的
- ensemble [ɑ:nˈsɑ:mbl] n. 整体
- gravitationally [ˌɡræviˈteiʃnəli] adv. 引力地
- interact [ˌɪntərˈækt] v. 相互作用
- orbit [ˈɔ:bit] v. 绕(吸引中心)运转
- unaided [ˈʌnˈeidid] adj. 独立的
- unaided eye [ʌnˈeɪdɪd - ai] n.肉眼
- Milky Way [ˈmɪlki: - wei] n.银河
- associated [əˈsəuʃieitid] adj.关联的
- cluster [ˈklʌstə] n. 星团
- atomic hydrogen gas [əˈtɔmik - ˈhaidrədʒən- ɡæs] n. 原子氢气
- molecular hydrogen [məˈlekjələ - ˈhaidrədʒən] n. 分子氢
- complex molecule [ˈkɔmpleks - ˈmɔlikju:l] n. 复杂分子
- nitrogen [ˈnaitrədʒən] n.氮
- silicon [ˈsilikən] n. 硅
- among others [əˈmʌŋ - ˈʌðəz] adv. 及其他
- cosmic ray [ˈkɔzmik - rei] n. 宇宙射线
- interstellar matter [ˈintə(:)ˈstelə - ˈmætə] n. 星际物质
