例句：

　　Space scientists and astronomers have taken another step forwards.

　　航天科學(xué)家和天文學(xué)家又取得了進(jìn)展。

　　Early astronomers thought that our planet was the centre of the universe.

　　早期的天文學(xué)家認(rèn)為我們的星球是宇宙的中心。

　　Astronomers know that Pluto and Triton have nearly the same size, mass, and density.

　　天文學(xué)家知道冥王星與海衛(wèi)一擁有幾乎相同的體積、質(zhì)量與密度。

　　Astronomers will have to collect more spectra from these stars to confirm their suspicions.

　　天文學(xué)家們必須要從這些恒星上采集更多的光譜來證實他們的推想。