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Ancient Earth hammered by double space impact


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Interesting that it calls the asteroids companion a moon; i've not started the moon course yet so will be interested to see what the criteria are for something to be categorised as a "moon".


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Isn't a "moon" an object that is controlled thru gravity and orbits the object that exerts the gravitational pull. Although I would have thought you could call the rings of Saturn moons using that definition. Fine line I guess - unless this "moon" also exerts a gravity field but they are not that big  :chin_scratch2:

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According to the course so far, a moon is an object of significant size which is gravitationally bound to a planet or dwarf planet etc not an object bound to the host star. To clarify, I mean an object that orbits a body which is orbiting the host star.


Pluto's moon is so large (in comparison with Pluto) that they are almost considered to be a binary dwarf planet.

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