Scientists Say: Dwarf planet

Some space objects look like planets but are too small to be one


Dwarf planets may not have enough gravity to clear their own paths, but they do have enough to bring in their own moons! This is dwarf planet Eris and its moon, Dysnomia. 


Dwarf planet (noun, “Dwarf PLAN-et”)

These are objects in space that are too small to be planets but too big to be asteroids. Like full-sized planets, dwarf planets have enough gravity to be round in shape. They orbit the sun or another star. But unlike planets, dwarf planets are too small for their gravity to clear other objects out its path. A planet is big enough that all of the asteroids and comets in its orbit have been pulled in or flung away by the planet’s gravity. But a dwarf planet doesn’t have enough gravitational power. Its orbit remains full of asteroids and other debris.

In a sentence

Being a dwarf planet doesn’t mean Pluto is just a chunk of rock; its heart shape could come from outside impacts or even internal tectonic plate activity.

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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