Dwarf Planets: Science & Facts About the Solar System’s Smaller Worlds

recent years, there’s been a lot of hubbub about Pluto losing its status as one of the planets of the solar system. Pluto is no longer considered the ninth planet in the series of major planetary objects, but instead is now just one of the many so-called “dwarf planets.” The debate started anew after the New Horizons mission passed by Pluto in 2015, revealing a world of surprising geological complexity. As of 2017, delegates from the mission are trying to getPluto’s planethood status back. 

Astronomers estimate that there could be as many as 200 dwarf planets in the solar system and theKuiper Belt. But the differences between planets and dwarf planets may not be obvious at first. 

Dwarf planets of the solar system

The International Astronomical Uniondefines a planet as being in orbit around the sun, has enough gravity to pull its mass into a rounded shape (hydrostatic equilibrium), and has cleared its orbit of other, smaller objects. This last criterion is the point at which planets and dwarf planets differ. A planet’s gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen. [Meet the Dwarf Planets of the Solar System]

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