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Use "protoplanetary" in a sentence
"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."