Just as optical astronomers observe the visible light emitted by objects such as stars and galaxies, radio astronomers can also observe the radio waves emitted by these objects, as well as the radio waves emitted by gas and dust. However, radio telescopes are different from optical telescopes in important ways. In general, compared to optical telescopes, radio telescopes are larger. more curved. more expensive. smaller. This is because

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.

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