Since childhood, it has been drilled into our heads that there are nine planets in the Solar System. However, there is nothing magical about the number 9, and it has always been assumed that there might be more planets lurking out there. Now, 75 years after Clyde Tombaugh discovered the ninth planet Pluto, a tenth one has been found:):). Observed through the Samuel Oschin Telescope at Palomar Observatory near San Diego, California, even though it is a typical member of the Kuiper Belt, it is possibly larger than Sedna (largest object beyond Neptune other than Pluto), has a moon, and thus is a planet in its own right.

Tenth Planet (Courtesy: CalTech)Tentatively named as 2003 EL61, the planet is about 97 times farther from the Sun than the Earth. It was first observed on October 31, 2003 and again observed in January of this year. In the last seven months, scientists have gathered enough data to make sure the size and orbit of the object, which conclusively pins it down as the tenth planet of the Solar System.
The size of the planet is limited by observations using NASA's Spitzer Space Telescope, which has already proved its mettle in studying the heat of dim, faint, faraway objects such as the Kuiper-belt bodies. Because Spitzer is unable to detect the new planet, the overall diameter of the planet has to be less than 2,000 miles. A name for the new planet has been proposed by the discoverers (Mike Brown, Chad Trujillo, and David Rabinowitz) to the International Astronomical Union, and they are awaiting the decision of this body before announcing the name:):).