How did ancient astronomers know to order the planets from the closest to the farthest from the Sun?
How can GAIA's accuracy for position, parallax, and annual proper motion for a given star be the same number?
At what latitude could Orion's belt and Aldebaran be ~10 degrees above the horizon at the same time?
Why does Sirius proper motion "wiggle" with a 1 year period, when Sirius A and Bs binary orbit is a 50 year period?
How was the Messenger spacecraft used to measure Mercury's orbital precession to such accuracy? Could this have been done using radar?
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