planetesimal vs heavenly body

planetesimal and heavenly body both are nouns.

Word	Noun	Adjective	Verb	Adverb
planetesimal	Yes	No	No	No
heavenly body	Yes	No	No	No

As nouns, heavenly body is a hypernym of planetesimal; that is, heavenly body is a word with a broader meaning than planetesimal:

planetesimal: one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system
heavenly body: natural objects visible in the sky

Other hypernyms of planetesimal include celestial body.

planetesimal (noun)	heavenly body (noun)
one of many small solid celestial bodies thought to have existed at an early stage in the development of the solar system	natural objects visible in the sky