The immediate cause of sudden cardiac arrest is usually an abnormality in your heart rhythm (arrhythmia), the result of a problem with your heart's electrical system.
Version for printing. The first planet to be discovered was Uranus by William and Caroline Herschel on 13 March 1781. It was discovered by the fact that it showed a disk when viewed through even a fairly low powered telescope. The only other planets which have been discovered are Neptune and Pluto.
American astronomer Clyde Tombaugh discovered Pluto in 1930. From 1930 until 2006, Pluto sat comfortably beyond Neptune as the ninth planet in our solar system. In 2006, however, changes were made. The truth is, nothing about Pluto changed, but the definition of a planet did.