Definition of protoplanet
: a hypothetical whirling gaseous mass within a giant cloud of gas and dust that rotates around a sun and is believed to give rise to a planet
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Recent Examples of protoplanet from the Web
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The idea is that a large protoplanet called Theia bumped into Earth about 4.4 billion years ago, knocking off a moon-sized cloud of debris that eventually coalesced into our favorite satellite.
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Somehow, the accretion disk of mostly hydrogen gas that surrounded the early sun coalesced into the rocky planets and asteroids in the solar system, and those protoplanets shed some elements in a process known as devolatilization.
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Though that’s not part of Dawn’s current mission, excitement about the potential for life on the protoplanet could one day fuel future exploration—and a better understanding of what once happened on Earth.
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Ceres is a protoplanet—a body that seems to be slowly developing into a planet.
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Eventually, some accrete enough mass to form protoplanets.
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Though that’s not part of Dawn’s current mission, excitement about the potential for life on the protoplanet could one day fuel future exploration—and a better understanding of what once happened on Earth.
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That sharp divide likely comes from the planet formation process, Fulton said: Planets' rocky cores form from smaller pieces, and then the protoplanet's gravity attracts hydrogen and helium gas.
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The idea is that a large protoplanet called Theia bumped into Earth about 4.4 billion years ago, knocking off a moon-sized cloud of debris that eventually coalesced into our favorite satellite.
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'protoplanet.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
First Known Use of protoplanet
1949
Learn More about protoplanet
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Britannica.com: Encyclopedia article about protoplanet
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