What is a Planet?

In 2006, the International Astronomical Union (IAU) redefined what it meant to be a planet. With increasing discovery in the Kuiper Belt, and Oort Cloud, the three criteria for an object to be classified as a planet are as follows:
1. is in orbit only around a sun.
2. sufficient mass for self gravity to create circular form and motion.
3. no comparatively sized objects in or near its orbit.
This definition gave us the four terrestrial and for gas giant planets that orbit the sun. it is also why there are only exoplanets named inside the Kuiper belt. Those objects, such as Pluto, do not meet the some criteria in naming an object a planet.
The most commonly used stellar wobble and transit methods has not allowed for much indetification of exoplanets, but the following three rules have made it possible to name any planet around any star when they meet the IAU criteria, including farther out into the Kuiper Belt:
1. the mass of a planet
2. The orbital distance/ period around its parent star
3. life time of planetary system in question.







Jewitt, Dave. "Dave Jewitt: Kuiper Belt: Surfaces of Kuiper Belt Objects." Dave Jewitt: Kuiper Belt: Surfaces of Kuiper Belt Objects. N.p., n.d. Web. 01 Dec. 2015.