The Four (Main) Subfields of Astronomy Research

The Four (main) Subfi

Photo Credits to Julia Busemeyer

elds of Astronomy

By: Julia Busemeyer

So, you want to be an astronomer… or astrophysicist… or aerospace scientist… or engineer… okay maybe you don’t know exactly what you want to be. But you know you want to study space. That’s an excellent place to start! If you’re in college or about to start your astronomy degree, though, it might be time to start thinking about exactly where you want to go with it. This can be wildly overwhelming-- trust me, you’re not alone in feeling that way! Astronomy can be an extremely convoluted field with countless paths and professions. This is your guide to some of the subfields of astronomy, complete with potential careers and and topics within them!

For your convenience, the subfields of astronomy outlined in this guide will be observational, theoretical, computational, instrumentation, and a few miscallaneous career paths that may be of interest to those intruigued by other aspects of outer space. In each section you can find a brief description of the subfield, a few examples of areas of study within the subfield, and some key components of working in the subfield. 

1. Observational Astronomy 

Observational astronomy is the study of celestial objects and astronomical phenomena through direct observation and analysis of recorded data (Number Analytics). Common areas of expertise in observational astronomy include exoplanet detection, spectral observations, and many more (Columbia). 

• Exoplanet detection involves looking for planets that orbit stars outside of our solar system. Believe it or not, according to NASA, there is very likely at least one planet orbiting every star in the universe. That’s a lot of planets to find. Astronomers have many ways of detecting exoplanets including the transit method (measuring the drop in brightness of a star due to a planet crossing in front of it), the radial velocity method (when a planet’s gravity causes its star to wobble, changing the way we observe the light), and direct imaging (taking pictures of a star and removing the glare as much as possible to see larger planets) (NASA).

  
  

• Spectral Observations have to do with looking at light from celestial bodies such as stars, nebulae, galaxies, and more. It’s a little more complicated than that, though, because we can’t see every wavelength of light with just our eyes. In fact, the visible light range on the electromagnetic spectrum is quite small! So, astronomers use different telescopes and other instruments to detect larger wavelengths with less energy (infared, microwave, and radio) and smaller wavelengths with more energy (ultra violet, x-ray, and gamma). The particular wavelengths of light being emitted by an object can tell us things about its composition, temperature, and density. By looking at the changes in an objects emitted wavelengths over time, we can also determine objects’ speed and the direction they’re traveling in. (NASA)

  
  

In general, observational astronomy is a mix of field work and data reduction. This means that if you choose to go into observational astronomy, you’ll have many late nights at your observatory. You’ll also spend lots of time looking through images, running and operating programs such as Astrometrica and AstroImageJ, and analyzing graphs and spreadsheets to make discoveries and contribute to collective data sets. You will also very likely learn a coding language like Python to aid your data processing. 

If you love real-time observing of the night sky and directly observing the cosmos, observational astronomy may be for you!

2. Theoretical Astronomy

Theoretical astronomy/astrophysics uses mathematical models and physical sciences like chemistry and physics to explain and predict astronomical phenomena (The Astronomy Enthusiast). Theoretical astronomy/astrophysics covers a wide array of topics including dark matter and stellar evolution (Harvard). 

• Dark matter is a “mysterious substance that affects and shapes the cosmos,” (NASA). We don’t know much more than that since we can’t see or directly detect dark matter, but we know it exists! As you’d imagine, learning more about dark matter is high on the priority list. Astrophysicists have been able to indirectly detect dark matter by observing its gravitational effects on objects we can see (CERN). For example, Kepler’s laws tell us that as you get further from the center of a galaxy, the rotation rate should decrease, but it’s actually uniform all the way through! We have predicted that this is the case because of dark matter around the edges of galaxies. Astrophysicists who study dark matter create models and theories to learn about dark matter and its behavior, as well as what it is and why we can’t directly find it (CERN). 

• Stellar evolution is simply how stars change throughout their lives. Stars live for millions of years, so we can’t directly observe a star’s entire life-- instead, we rely on our understanding of nuclear physics, chemistry, observation of different types of stars, and more to put the pieces together (AAVSO). Those who study stellar evolution often look at structures like planetary nebulae, the remnants of low mass stars, to understand how the star shed its layers, its composition, and more (Harvard). They may also look at the end-stages of high mass stars, including black holes, neutron stars, pulsars, and more. All efforts in stellar evolution help us better understand the most prolific structure in our universe. 

While the work of an astrophysicist varies greatly between “specialties,” if you choose to go down this path, you’ll see a lot of math, coding, model building, simulations, and more. Like in observational astronomy, you’ll have to be proficient in analyzing data, but you’ll also need a thorough understanding of physics and math. Particularly nuclear physics, quantum physics, and even chemistry (EBSCO). 

If you love answering questions about the universe and have a strong affinity for math, physics, and coding, theoretical astronomy/astrophysics may be for you!

3. Computational Astronomy

Computational astronomy works hand-in-hand with theoretical astronomy/astrophysics. What theoretical astrophysicists can’t do with pure math and observational astronomers can’t observe, computational astronomers simulate (Harvard). This branch of astronomy is about creating a way to observe the objects and phenomena we otherwise couldn’t. Computational astronomers design simulations and models for many astronomical happenings including planet formation and galaxy evolution (Columbia). 

• Planet formation happens in a young star’s accretion disk (gas, dust, and other particles orbiting the star; not unlike stars orbiting the black hole in the center of a galaxy!). In the accretion disk, some small particles combine and keep combining with other clumps and pebbles, eventually growing into small masses called “planetisemals,” (NASA). Depending on distance from the star, these planetisemals can become ice/gas giants (like Jupiter and Neptune), or rocky planets (like Earth and Mars) (NASA). Simulations of planet formation help us better understand the process, which in turn helps us learn about the formation of the Earth and even how a planet becomes habitable (Harvard).

  
  

• Galaxy evolution tells us how galaxies like the milky way form, change, and what their fate may be. There are many questions astronomers have about galaxy evolution/formation. For example, NASA says there is a black hole at the center of most large galaxies and asks: did the galaxy form around the black hole or did the black hole grow and drift after the galaxy was formed? These are scenarios a computational astronomer may attempt to simulate. They also may simulate galaxy collisions and other galactic interactions to observe the process and result.

The work of a computational astronomer is completely reliant on computer and math skills (Harvard). If you choose to go into computational astronomy, you will have to be very comfortable with coding. Most astronomers choose Python as their primary coding language, but others are often used as well (Physics World).

If you love computer science and attempting to explain/predict the unknown, computational astronomy may be for you!

4. Instrumentation

You guessed it! Instrumentation in astronomy is all about the tools and instruments we need to conduct astronomical research. There are many components to instrumentation including design, building, and testing new instruments, all to ensure accurate and clear results when other astronomers actually use them (Harvard). Instrumentation in astronomy deals with a large variety of tools, though two of the most common are telescopes and cameras.

• Telescopes come in countless shapes and sizes. The two main types of optical telescopes are refractors, which use lenses to focus light from space, and reflectors, which rely on mirrors (OPT). Designing and building telescopes is more than just lenses and mirrors, though. There are optical telescopes, which detect light in the visible wavelengths, X-ray telescopes such as NASA’s Chandra X-ray Observatory, which, as the name suggests, makes observations in the X-ray wavelength, and telescopes like the James Webb Space Telescope which have a near-mid infrared detection ability, among many others. The point is, telescopes all have different functions and purposes, all of which must be created by instrumental astronomers. 

  
  

• Cameras are incredibly important for research in astronomy and astrophysics because they not only allow us to keep a record of what we’ve observed, but special cameras called CCDs (charge-coupled devices) detect individual photons so we can go back and measure things like brightness (Las Cumbres Observatory). CCDs also often have filter wheels for optical telescopes so we can image objects in different wavelengths, observe differences between wavelengths,  and create color images. The accuracy and integrity of CCDs and other cameras is crucial to obtaining excellent data, so instrumentation is incredibly important here. 

  
  

Designing and building such instruments is a very hands-on career option that requires an understanding of optics, mechanics, computer science, and mathematics. Instrumentation is less about actually looking at and analyzing objects/phenomena in space and more about making it all possible. That being said, when designing instruments and tools for astronomy, you have to know what the end goal is so you can create the best equipment! So, a thorough understanding of astronomy is still incredibly important. 

If you love electronics, design, and the idea of a more hands-on approach to exploring the cosmos, instrumentation may be for you!

Now, there are many, many more branches and subfields of astronomy than just these four. So, if none of these struck a chord for you, don’t stress! There is an astronomy job out there for you! Some other options you may look into include space physics, aerospace science or engineering, flight control, materials science, and more. There are also plenty of space-related careers in communications, marketing, business, and more, if STEM isn’t your cup of tea. Regardless, I can guaruntee there is a place in the field for you! Don’t be afraid to do your own research, reach out to your professors/mentors for advice, and experiment with different careers through internship experiences. You’ll never know what path is best for you if you don’t let yourself explore the field and try new things!