氢行星hydrogen planet 双行星 the double planet; twin planet ..
双语例句
1
Like its bigger neighbor Jupiter, Saturn is a gas planet made mostly of hydrogen and helium.
就像比它更大的邻居-木星一样，土星也是气体行星，主要由氢和氦所组成。
2
Having said that, we suspect that this new planet is made mostly of hydrogen and helium gas.
这样说来，我们猜测这可新发现的行星主要由氢气和氦气组成。
3
If a rocky planet is big enough - say, 10 times the mass of Earth - it can vacuum up so much hydrogen that its atmosphere ends up constituting most of the planet.