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.

The New Challenge

The discovery of the Kuiper belt has lead to many more questions about the objects contained in it. Much like the classifications of the eight planets, scientists are uncovering the sizes and colors and the moons and atmospheres of Kuiper Belt Objects (KBOs). One particularly suggested questions, by previously mentions David Jewitt, is about the surface of these objects. In his studies, Jewitt has found a large array of colors using low resolution spectra data. He proposes two explanations of the wide diversity of color. First, that the diversity in color represents the diversity of the composition of objects. Second, the process of "collision resurfacing" ( impact craters create ray of light on other material, distorting color of said material), creating the diversity in color.

Further study from the scientific community has lead the the conclusion as to why the color and reflectiveness are important in obtaining information about the surface of KBOs. The variety of color identifies the composition and evolution of KBOs. Although it is still difficult to identify specific minerals and ices, the revelation of color diversity is an important step in discovering what the surfaces of KBOs are comprised of.       

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. 28 Nov. 2015.

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. 28 Nov. 2015.