protoplanet

例句：

1. 1.The discovery of protoplanets has opened up new possibilities for space exploration.
   发现原行星为太空探索开辟了新的可能性。
2. 2.The study of protoplanets is crucial to understanding the origins of life on Earth.
   研究原行星对理解地球上生命的起源至关重要。
3. 3.Astronomers have been searching for protoplanets in the habitable zones of nearby stars for decades.
   天文学家已经花了几十年的时间在附近恒星的宜居带中寻找原行星。