In this picture, the Earth-moon system actually appears to be a double planet.

照片中，地月系统实际上看上去像一颗双行星。

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As the Givin developed intellectually, they perfected complex forms of mathematics to help predict the bizarre moon system orbiting Yag'Dhul.

随着吉文人高度智慧化，他们完成了形式复杂的数学体系，以预测亚格杜尔星轨道上奇异的卫星系运动。

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The Earth-Moon system has always been perplexing.

地月系统一直令人困惑。

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"We'll be keeping an eye out for signs of a repeat performance next year when the Earth-moon system passes through the same region of space, " Cooke said.

CNN: Bright explosion on moon visible from Earth, NASA says

But in constructing the first atmospheric model that has the orbital dynamics of a star-planet-moon system fully included, astronomers Duncan Forgan, at the Royal Observatory in Edinburgh, and David Kipping, at the Harvard Smithsonian Center for Astrophysics in Cambridge, turn that idea on its head.

FORBES: Earth-Like Exo-Moons Can Lurk Well Beyond Planetary Habitable Zones, Say Astronomers

It also found that Ganymede, the largest moon in the solar system, has a magnetic field.

ECONOMIST: Galileo and Jupiter