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What role does hydrogen play in spectral classification?
Q18: If a star appears to move back
Q29: What physical property of a star does
Q32: Many of the brightest stars we see
Q45: Orbital resonances are a characteristic of some
Q68: As with Saturn's F ring,shepherd moons play
Q87: Collisions between galaxies tend to destroy,not create,stars.
Q91: Three terrestrial-sized planets in orbits of a
Q97: Which of these does NOT exist?<br>A) a
Q100: A system of terrestrial-sized planets has been
Q107: The brightest stars in a young open