The Difference between Astronomy and Astrophysics

Astronomy is the oldest science. Astrophysics is relatively new. Astronomy is the root science and astrophysics is a branch. Theoretically, astronomy is the study of bodies in space; astrophysics is the study of physical processes in space. One way to remember the difference between astronomy and astrophysics is to think of star gazing, developing star charts and considering what stars are made as astronomy. Calculating how a star may become a black hole falls into the category of astrophysics.

Early astronomy is evident in the construction of Stonehenge in 3100-2000 BC, a possible astronomical observation site. Early astronomers also include Chinese with recorded activity beginning in 1300 BC. The Chinese tracked various celestial events like the appearance of guest starts. One of those guest stars recorded in 240 BC is what is now known as Comet Halley. The Maya calculated movement of stars through the heavens and developed sophisticated calendars documented in stelas from as early as 200 BC. These astronomers could observe where starlight originated and observe their track through the skies with the naked eye. The father of modern astronomy, Copernicus, published his theory that the sun was the center of the solar system in 1543. The invention of the telescope in the early 1600s revolutionized stargazing and Galileo, armed with his improved version of the device, proved the accuracy of Copernicus’s theory.  

Studies in astrophysics began in the mid-nineteenth century when knowledge of light and chemistry and telescopes coincided and merged. Astrophysicists are more involved with specific details about starlight that provide information about the physical property of light from the stars, what stars could be made of, and distance and motion of heavenly bodies.  The Father of Astrophysics, Angelo Secchi, S.J, lived from 1818-1878 and advanced stellar spectroscopy with tools that let astrophysicists calculate much information about the properties, physical and chemical, of stars. Astrophysicist Dr. Ignacio Mosqueira explains succinctly that “an astrophysicist studies celestial objects and the universe using the laws of physics. However, nowadays physicists also tackle such questions, so the distinction between the two disciplines is becoming blurry.”

Academic rigor for a career in astronomy includes requirements for physics or similar disciplines, further melding the two fields of study. American Institute Of Physics survey of 1996 revealed that “63 percent of astronomers had an undergraduate degree in physics, 26 percent in astronomy, and the rest in engineering and other physical sciences.” Astronomy and astrophysics both focus on the study of elements beyond the Earth’s atmosphere. Simply stated, astronomy focuses on finding what is out there. Astrophysics focuses on how what’s out there works.