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Questions regarding Charon, the largest satellite of the dwarf planet Pluto. Often considered to be Pluto's binary.
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about the lack of evidence for alien life, despite the growing evidence that suitable planets are reasonably plentiful.
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Questions about Europa, a moon of Jupiter with a planet-wide ocean under a thick ice crust.
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Questions about gas-giant planets in very close orbit to their parent star (closer than Mercury).
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the group of galaxies that includes the Milky Way among others.
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Space debris (also known as "orbital debris", "space junk", or "space waste") is the collection of defunct objects in orbit around Earth and includes everything from spent rocket stages, old satellite…
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Questions regarding a theoretical 'tunnel' through spacetime which could potentially allow time travel.
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