So, by not collapsing into denser regions, these massive nebulae, like the 100,000 solar mass California Nebula shown above, don't necessarily start making baby stars and planets.
所以如果不被压缩到很致密，这些大质量星云，比如有太阳质量100，000倍的California星云，则不一定会形成新生恒星和行星。
L the Ring nebula in Lyra is the best-known of the planetary nebulae.
l天琴座中的环状星云是最著名的行星状星云。
The Cat's Eye nebula (NGC 6543) is one of the best known planetary nebulae in the sky.
猫眼星云(NGC 6453)是天空中最著名的行星状星云之一。
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