Are Astronomy, Astrophysics and Astrology All the Same?

The Jewelbox Cluster
Astronomy and astrophysics are the sciences that help us understand the workings of the stars and galaxies. European Southern Observatory

People often confuse astronomy and astrology, not realizing that one is a science and the other is a parlor game. Astronomy itself covers both the science of stargazing and the physics of how stars and galaxies work (which is often referred to as astrophysics). Astronomy and astrophysics are often used interchangeably by those who do know the difference.  The third term, astrology, refers to a hobby or parlor game. It is mistakenly used by many people to refer to astronomy. However, there's no scientific basis in the current practice of astrology, and shouldn't be mistaken for a science. Let's take a more detailed look at each of these subjects. 

Astronomy and Astrophysics

The difference between "astronomy" (literally "law of the stars" in Greek) and "astrophysics" (derived from the words Greek words for "star" and "physics") comes from what the two disciplines are trying to accomplish. In both cases, the goal is to understand how objects in the universe function. 

Astronomy describes the motions and origins of the heavenly bodies (stars, planets, galaxies, etc.). It also refers to the subject that you study when you want to learn about those objects and become an astronomer.  Astronomers study the light emanating or reflected from distant objects

Astrophysics is literally the physics of the many different types of stars, galaxies, and nebulae. It applies the principles of physics to describe the processes involved in the creation of the stars and galaxies, as well as learning what drives their evolutionary changes. Astronomy and astrophysics are definitely interrelated, but are clearly trying to answer different questions about the objects they study. Think of astronomy as saying, "Here's what all these objects are" and astrophysics as describing "here's how all these objects work." 

Despite their differences, the two terms have become somewhat synonymous in recent years. This can be attributed to the fact that most astronomers receive the same training as astrophysicists, including the completion of a graduate program in physics (although there are many very good pure astronomy programs being offered).

Much of the work done in the field of astronomy requires the application of astrophysical principles and theories. So while there are differences in definitions of the two terms, in application it is difficult to distinguish between them. If you study astronomy in high school or college, you will first learn purely astronomy topics: motions of celestial objects, their distances, and their classifications. To understand them, you need to study physics and eventually astrophysics. Generally, once you start to seriously study astrophysics, you're well on your way through graduate school. 


Astrology (literally "star study" in Greek) is largely regarded as a pseudoscience. It does not study the physical characteristics of stars, planets, and galaxies. It is not concerned with applying principles of physics to the objects it uses, and it has no physical laws that help explain its findings. In fact, there's very little "science" in astrology. Its practitioners, called astrologers, simply use the positions of stars and planets and the Sun, as seen from Earth, to predict people’s individual characteristics, affairs and future. It's largely akin to fortune-telling, but with a scientific "gloss" to give it some kind of legitimacy. In truth, there's no way to use stars and planets to tell you anything about a give person's life or loves. If you could, then the rules of astrology would work everywhere in the universe, but they'd still be based on the motions of one specific set of planets as seen from Earth. It doesn't make a lot of sense when you think about it.

While astrology has no scientific basis, it did play a preliminary role in the development of astronomy. This is because early astrologers were also systematic stargazers who charged the positions and motions of celestial objects. Those charts and motions are of great interest when it comes to understanding star motions and planetary motions today. However, astrology diverges from astronomy because astrologers use their knowledge of the sky to "predict" future happenings. In ancient times, they did this mostly for political and religious reasons. If you were an astrologer and could predict some wonderful thing for your patron or king or queen, you might get to eat again. Or get a nice house. Or some gold. 

Astrology diverged from astronomy as a scientific practice during the years of the Enlightenment in the Eighteenth Century, when scientiific studies became more rigorous. It became clear to scientists of that time (and ever since then) that no physical forces could be measured emanating from stars or planets that could account for the claims of astrology.

In other words, the position of the Sun, Moon and planets at a person's birth have no effect on that person's future or personality. In fact, the effect of the doctor assisting with the birth is stronger than any distant planet or star. 

Most people today know that astrology is little more than a parlor game. Except for astrologers who make money off of their "art", educated people know that the so-called mystical effects of astrology have no actual scientific basis, and have never been detected by astronomers and astrophysicists.