Astronaut Neil Armstrong is recovering from heart surgery, according to The Associated Press.
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Armstrong, 82, who became the first man to walk on the moon in 1969, reportedly had cardiac bypass surgery recently although it's not clear exactly when.
Edwin "Buzz" Aldrin, who was aboard Armstrong's legendary Apollo 11 spacecraft, tweeted, "Sending my best wishes for a speedy recovery."
Armstrong's last major public appearance came in February at Ohio University where he honored fellow astronaut John Glenn.