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.
Pluto was discovered in 1930 by U.S. astronomer Clyde Tombaugh. For many years, Pluto was called a planet. It was the smallest planet in the solar system and the ninth planet from the sun. Today, Pluto is called a dwarf planet. A dwarf planet is round and orbits the sun just like the eight major planets.