Astronomy vs Astrophysics: Are They the Same?

For thousands of years, humankind has directed its gaze upward toward the skies and pondered the significance of celestial bodies in the heavens above. Today, that torch has been passed on to astronomers and astrophysicists who continue the ageless study of the cosmos, albeit with modern tools and equipment. Are the fields of astronomy and astrophysics actually the same thing, though?

Both astronomy and astrophysics seek to understand phenomena that have been observed high up in the skies since the dawn of humankind. But where astronomy is a broad field of celestial studies, astrophysics is a discipline that relies on advanced physics to analyze data and reach conclusions.

For millennia, people have sought answers to fundamental questions about the universe, and thanks to modern science, much has been learned about the universe, its origins, and the phenomena it contains. And while there are plenty of mysteries that are yet to be solved, one thing that is certain is that the path leading to answers runs through astronomy or astrophysics, or perhaps even both. Here’s how.

Are Astronomy and Astrophysics the Same?

The first known recordings demonstrating that humans observed the cosmos have been dated as far back as 30,000 years ago with what are believed to be renderings of constellations. In a sense, these ancient stargazers were the very first astronomers, and relying only on the naked eye and their keen sense of observation, they were able to draw incredible scientific conclusions including:

• The moon periodically changes its shape and position among the stars
• Two arrangements of stars (constellations) could always be seen encircling the North Pole – these would turn out to be the Little Dipper (Ursa Minor) and the Big Dipper (Ursa Major)
• They observed the same bright star in the mornings and evenings and concluded that it was the same celestial body (the planet Venus)
• Aristotle of Stagira surmised in the 4^th century B.C.E. that the earth is round based on his observations of eclipses as the earth passed between the sun and moon
• Eratosthenes also theorized the earth’s round shape based on the different ways that shadows formed in different locations, but most notably, he correctly theorized that the earth’s circumference is 25,000 miles (it is actually 24,901 miles)

Naturally, there would have been no distinction between astronomy and astrophysics back then as the fundamental principles of physics would not have been discovered until thousands of years later. Fast forward to the modern era, and there are several schools of thought regarding astronomy and astrophysics and whether they are, in fact, the same thing.

Technically speaking, this is how these two scientific disciplines are defined from an academic perspective:

• Astronomy is the study of the universe lying beyond the earth’s atmosphere and is commonly viewed as comprising three primary disciplines: astrometry, celestial mechanics, and astrophysics (in recent years, additional sub-fields have been added – more on this later)
• Astrophysics is a branch of astronomy dealing primarily with the physical aspects of celestial bodies and the various forms of energy that are involved in their creation, existence, and demise

Thus, astronomy can be viewed as a broader field of study that encompasses not only astrophysics but also other distinct scientific disciplines as well. Practically speaking, however, there are many who are of the view that the line separating astronomy and astrophysics is not so clearly defined, and they are essentially one and the same scientific domain.

As their argument goes, most astronomers routinely rely on physics in their duties and since by most definitions it is the use of physics that distinguishes the two, for all intents and purposes, they are the same. But while there are strong parallels between astronomy and astrophysics, there are also key distinctions that can be made. This makes each worthy of a closer look.

What is Astronomy and What Does an Astronomer Do?

Considering that it is the investigation and exploration of all that lies outside of the earth’s atmosphere, the sheer vastness of what astronomy encompasses is difficult to fathom. To an ordinary layperson, astronomy can be summed up as the study of planets, stars, galaxies, and other celestial bodies.

But in reality, astronomy is an expanding collection of scientific disciplines that can be broken down into two main categories:

• Observational astronomy gathers data about the universe using sophisticated telescopes and cameras
• Theoretical astronomy then uses that information to develop theories and gain a deeper understanding of how the universe works

Within these two branches of astronomy are a number of sub-fields, each focusing on a particular aspect of studying and understanding everything that exists in the known (and yet to be discovered) universe. These can be summarized thusly:

• Astrometry – practiced by ancient astronomers, this discipline may be the oldest form of astronomy and it seeks to predict the movements of celestial bodies like the sun, moon, and other planets, and also tracks occurrences like solar and lunar eclipses, along with meteor showers
• Planetary astronomy – this discipline focuses on the birth, development, and extinction of planets, moons, and other bodies in the cosmos, within the context of understanding how our own solar system came into being
• Astrophysics – through the lens of physics, astrophysics seeks to understand and explain the various mechanisms and processes through which the universe was created and continues to develop and expand (more on this later)
• Astrochemistry – the focus in this sub-field is the makeup and behavior of atoms, molecules, and ions in outer space
• Astrobiology – this fledgling field of study is for the most part theoretical in nature and seeks to answer the question of whether there are other forms of life elsewhere in the vast expanses of the universe
• Stellar astronomy – stars (like our own sun) are the primary focus of this discipline, which investigates their full life cycle from birth to death, studies their makeup and classifications, and tracks their numbers throughout the known cosmos
• Solar astronomy – this sub-field is broken down into two groups: galactic astronomers who study our own Milky Way galaxy, and extragalactic astronomers, whose focus lies on faraway galaxies; both seek to learn how these systems are created, evolve, and eventually die
• Cosmology – answering the big questions relating to the origin of the universe and its evolution, is the focus of cosmology; this discipline has given rise to well-known scientific theories like the Big Bang Theory and comprises purely theoretical concepts like dark matter, string theory, and dark energy

In addition to comprising these eight disciplines, the term astronomy is also used in several ways to describe the particular technology that is used to make observations about the universe and gather data. These pertain to specific parts of the electromagnetic spectrum and the ones that astronomers currently use are:

• Optical astronomy – this encompasses the visible light spectrum and utilizes powerful telescopes (the largest telescopes on the planet are of this particular variety)
• Infrared astronomy – infrared light requires the use of space-based observatories, including the likes of the Hubble Space Telescope and the more recently launched James Webb Space Telescope
• Radio astronomy – radio waves are another means of studying objects in deep space and radio telescopes are used to amplify radio frequencies detected from far reaches of the cosmos

As astronomers gain a deeper understanding of the cosmos and everything in it, so too are new technologies emerging to bolster these efforts. The James Webb Space Telescope promises to pull back the curtain on the mysteries of the universe further than ever before, while enormous earth-based observation projects, like the world’s largest radio telescope, should soon be coming online.

What Does an Astronomer Do? Here’s a Glimpse

Like many of their peers in other scientific disciplines, much of what an astronomer does on a day-to-day basis is conducting research, gathering data, and performing scientific analysis to reach evidence-supported conclusions.

And of course, astronomers spend a significant amount of their time observing the skies with the aid of powerful telescopes, many of which are located in extremely remote areas so as to provide pristine views free from any light pollution from populated areas. An astronomer’s duties while stationed at a research facility or observatory would likely include:

• Coordinating research objectives with peers and colleagues
• Reviewing coordinates for upcoming observations and evaluating atmospheric conditions to determine their scheduling and prioritizing
• Programming and operating the telescope (along with the telescope operator) to perform observational requests submitted by astronomers around the world
• Monitoring instruments and equipment to ensure that they are in good working order

Astronomers are much more than just stargazers, but in a way, that is the very essence of what they do.

What is Astrophysics and What Does an Astrophysicist Do?

It can be said that astrophysicists, astronomers, and cosmologists seek answers to the same questions, but from differing perspectives. To illustrate these nuances, take the hypothetical problem of locating a far-off nebula. Here’s how astrophysics, astronomy, and cosmology might contribute in their own unique way to answering this question:

• The astrophysicist would seek answers relating to the mechanics and processes of how the nebula was formed and its physical and chemical makeup
• The astronomer may seek to observe and measure the amount of light emitted by the object to ascertain its characteristics
• Last but not least, the cosmologist would apply the data and findings to determine how the nebula fits within the larger framework of the universe

An astrophysicist applies the principles of physics (and in some cases, other disciplines like chemistry as well) to understand objects and phenomena in the cosmos and develop theories to explain them. Although it, like other branches of astronomy, is an ever-evolving field of study, some of the basic questions addressed by astrophysics relate to the creation, formation, and extinction of:

• Stars
• Planets
• Galaxies
• Nebulae
• Other objects and phenomena, whether known to exist or simply theorized

Where the birth of astronomy can be traced back thousands of years to ancient stargazers, astrophysics by comparison is a relatively new discipline and its formation as a recognized science is by and large attributed to Isaac Newton. It was Newton’s theory about gravity that opened the door to game-changing concepts about the workings of the universe, many of which are rooted in astrophysics:

• Some celestial objects are so distant that the only trace of their existence is the radiation they emit, and it is astrophysics that enables their study
• Astrophysics has given rise to spectral analysis and spectroscopy as essential tools in the observation and study of celestial bodies
• The concept of the Doppler shift and Einstein’s theory of relativity have given astrophysicists the ability to predict the behavior of stars and planets
• Newer fields of study such as nuclear physics, quantum mechanics, and particle physics can all be attributed to the evolution of astrophysics

According to one of the world’s preeminent space agencies, the National Aeronautics and Space Administration (NASA), astrophysics is an instrumental tool in humankind’s quest to answer these three fundamental questions about the universe:

• How does the universe work – investigating the formation of stars, planets, galaxies, and everything else the universe holds and unlocking the mysteries of phenomena like black holes, dark energy, gravity, and dark matter
• How did we get here – trace the history of the universe all the way back to its origins and learn how everything began
• Are we alone – discover how planetary systems form, investigate the possibilities of life-sustaining environments existing elsewhere in the cosmos and answer the ultimate question of whether we are alone in the universe?

As far as what the future of astrophysics holds, long-term objectives include searching for the universe’s very first stars, adding to the more than 3,800 currently mapped planets, and of course, finding celestial bodies capable of supporting life.

What Does an Astrophysicist do Exactly?

While the day-to-day duties and responsibilities of one astrophysicist can vary wildly from those of another, generally speaking, they tend to work in one of several capacities:

• As a full-time researcher at a university or observatory
• Being a data scientist at an institution
• Extensive programming and data analysis
• Working as a professor

The common thread tying all of these together is the application of the laws and theories of physics to ask the right questions and obtain answers to them.

Should I Major in Astrophysics or Astronomy?

Both astrophysics and astronomy require a natural curiosity for all things celestial and a commitment to learning and adhering to a science-based process. But from an academic standpoint, where the paths of astrophysics and astronomy diverge has much to do with the breadth and scope of the studies you desire to take:

• Astronomy is a broader field that encompasses broader studies and allows for more flexible career goals
• Astrophysics is generally more academically rigorous and typically appeals to those who are committed to a career centering on full-time research and academia

Given the nature of astrophysics, undergraduate studies would consist of a heavy dose of hard science courses like physics and chemistry, as well as advanced courses in mathematics, quantum mechanics, and thermodynamics. Generally speaking, this is a field for those seeking to make their mark on an academic level and contribute in a scholarly way to further the development of this discipline.

Majoring in astronomy would also entail science and mathematics courses, along with a curriculum designed to develop problem-solving skills and understanding physical mechanics, but not quite to the extent that an astrophysics major would be expected to undertake. Those with an insatiable sense of curiosity and a desire to explore not just the cosmos but experience new locales here on earth may be well suited for a career in astronomy.

Conclusion

In a broad sense, astronomy and astrophysics aim to answer the same fundamental questions about the universe. But where astrophysics relies on concepts rooted in physics to analyze and explain the mechanics of celestial bodies and cosmic phenomena, astronomy looks at the universe through a much larger lens to gain insight into the bigger picture.