他们记录了行星形成前，太阳系的历史，并且是第一个围绕我们原太阳的固体凝结的气体星云。
'They recorded the history of the solar system before any of the planets formed, and were the first solids to condense out of the gaseous nebula surrounding our protosun.'
他们的形体能达到多大取决于他们离恒星的距离和原行星星云的组成。
How big they get depends on their distance from the star and the density and composition of the protoplanetary nebula.
这是哈勃望远镜拍摄到的猎户星云中的原行星盘(proplyds，protoplanetarydisks)。
A Hubble Space Telescope image shows "proplyds, " or protoplanetary disks, in the Orion Nebula.
如果一个原行星足够大，形成足够快，它的重力会拉入星云的气体，它就会变成一个巨型气体行星。
If a protoplanet was large enough, soon enough, its gravity would pull in the nebular gas, and it would become a gas giant.
如果一个原行星足够大，形成足够快，它的重力会拉入星云的气体，它就会变成一个巨型气体行星。
If a protoplanet was large enough, soon enough, its gravity would pull in the nebular gas, and it would become a gas giant.
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