↑Keeler, James E. (November 1897), "The Importance of Astrophysical Research and the Relation of Astrophysics to the Other Physical Sciences", The Astrophysical Journal: An International Review of Spectroscopy and Astronomical Physics6 (4): 271–288, Bibcode:1897ApJ.....6..271K, doi:10.1086/140401, "[Astrophysics] is closely allied on the one hand to astronomy, of which it may properly be classed as a branch, and on the other hand to chemistry and physics.… It seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space–what they are, rather than where they are."
↑"astrophysics". Merriam-Webster, Incorporated. Archived from the original on 10 June 2011. สืบค้นเมื่อ 2011-05-22.