astronomer vs Friedrich Wilhelm Bessel

astronomer and Friedrich Wilhelm Bessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
astronomer	Yes	No	No	No
Friedrich Wilhelm Bessel	Yes	No	No	No

astronomer (noun)	Friedrich Wilhelm Bessel (noun)
a physicist who studies astronomy	German mathematician and astronomer who made accurate measurements of stellar distances and who predicted the existence on an 8th planet (1784-1846)