Definition of "protoplanetary" [protoplanetary]

• Of or pertaining to a protoplanet. (adjective)

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• "In order to determine whether the surface of an extrasolar planet would contain water, scientists can look at what is called the protoplanetary disk - a disk of gas and dust surrounding a star during its early stages of development."
• "For those of you scoring at home, "planetesimals" were the first solid objects in our newly minted solar system (also known as the protoplanetary disk)."
• "Now researchers have probed whether or not the necessary precursor to planet formation - a so-called "protoplanetary" disk of planet building blocks - could survive in this environment."