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explanation:

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when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

blue stars have the highest surface temp

stellar distances are usually expressed in light-years

the measure of a star's brightness is called magnitude

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a compound light microscope is used to magnify objects in steps.  

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