Since then a different planet has moved to the forefront of gas-mining plans because it lacks Jupiter's intense gravity, Saturn's gigantic rings of orbital debris and is closer than distant Neptune.
A rare galaxy type, polar ring galaxies have a substantial population of stars, gas, and dust orbiting in rings nearly perpendicular to the plane of the galactic disk.
极环星系是种稀有的星系类型，它们有着几乎和银盘平面垂直，呈环形公转的大量的恒星、气体和星尘。
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You have to mix oil into the gas in a two-stroke engine because the holes in the cylinder wall prevent the use of rings to seal the combustion chamber.