Within a year of opening, it was used to determine the planet Mercury's period of rotation. The astronomers Joseph Taylor and Russell Hulse discovered the first binary pulsar at Arecibo in 1974, leading to a 1993 Nobel Prize in physics. In 1990, Polish astronomer Aleksander Wolszczan used the telescope in the discovery of a pulsar in the constellation Virgo that was shown to be orbited by the first known planets beyond Earth's solar system.
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