PROTOPLANET hypothesis


Study Skills

Directions: Read and analyze the given information below. Write your analysis and make a conclusion based on the information gathered.

Pluto: a planet? How is it classified?

Figure 1.14 Earth's and Venus's Rotation

The Kuiper belt, which is made up of a scattering of stony and icy bodies, is located at the very edge of the solar system. The Oort cloud, a zone packed with minuscule and dispersed ice traces, lies beyond that. Most comets develop and continue their orbits in these two areas, and objects found here have relatively erratic orbits compared to the rest of the solar system. Pluto, once known as the ninth planet, is located in this part of the universe. Pluto was demoted to dwarf planet status by the International Astronomical Union (IAU) during its XXVIth General Assembly in 2006 after astronomers discovered Eris, a more massive object than Pluto. The International Astronomical Union decided against including Eris as a planet, and as a result, Pluto was also left out. The IAU narrowed the definition of a planet to three criteria:

  1. Enough mass to have gravitational forces that force it to be rounded

  2. Not massive enough to create a fusion

  3. Large enough to be in a cleared orbit, free of other planetesimals that should have been incorporated at the time the planet formed. Pluto passed the first two parts of the definition, but not the third. Pluto and Eris are currently classified as dwarf planets.