Spanish scientist professor Carlos de la Fuente Marcos, from the Complutense University of Madrid, believes there are two or more Earth sized planets beyond Pluto. Beyond Pluto lies the Kuiper Asteroid Belt, where small asteroids are moving in an unexpected orbit. This should only happen when there is a larger body to pull in smaller objects due to the gravity of a larger body. Although there are three dwarf planets beyond Pluto (Eris, Haumea, & Makemake) and one located in the asteroid belt between Mars and Jupiter (Ceres), the objects Professor Marcos believes he has spotted are Earth sized or larger. To put that in perspective Pluto (1,151km radius) is one sixth the size of Earth (6,371km radius). The only dwarf planet in our solar system that isn't smaller than Pluto is Eris (1,163km radius), which is thought to be slightly larger.
image source: space.com (http://www.space.com/18584-dwarf-planets-solar-system-infographic.html)
Further evidence of these planets may come from the New Horizons mission launched by NASA on January 19 2006. The New Horizons craft will arrive at Pluto this summer (Summer 2015) and observe it to better understand planets that orbit the outer edge of our solar system. Once the observation is complete New Horizons will then make its way past Pluto to observe objects in the Kuiper Belt. This may lend more insight to Professor Carlos de la Fuente Marcos theory of distant Earth sized planets orbiting within our solar system.
original article source: The Independent (http://www.independent.co.uk/news/science/two-earthsized-planets-could-be-hiding-in-our-solar-system-9987002.html)
