What Is The Difference Between Cosmology And Astronomy?

What Is The Difference Between Cosmology And Astronomy?

If you’re interested in astronomy, you might wonder how it varies from cosmology.

Maybe you’ve even thought that they’re pretty much the same thing, but they’re actually quite different.

Are cosmology and astrology connected?

Cosmology is a subsection of astronomy, which is why the two share some similarities. However, there are important differences to know about them.

With that in mind, let’s explore the study of the universe by looking at what cosmology and astronomy are and how they differ from each other. Understanding their differences will put their work and the universe into better perspective.


Cosmology vs Astronomy: What Are The Differences?

Astronomy can be broadly defined as the study of everything in the universe. It focuses on determining the nature of things on a small scale, such as how individual stars and planets have evolved.

But it’s also the study of the planets, moon, comets, stars, and other heavenly bodies, as Space reports. 

While it can concentrate on the nature of things on a small scale, it also looks at the nature of things on a larger scale, such as when it comes to galaxies and galaxy clusters.

What Is Astronomy

  • Focuses on motion and the relative positions of celestial objects.
  • Predicts the planets’ positions, meteor shows, and eclipses.
  • Makes use of celestial mechanics as well as optics to understand the composition of celestial objects.

What Else Should You Know About Astronomy?

There are two types of astronomers

Theoretical astronomers

These people create models to analyze how systems in the universe have grown and changed.

So, they’re focused on measuring the implications of these models, which is important because it helps scientists to discover phenomena that would never be understood otherwise and also learn about their effects.

Observational astronomers

These scientists concentrate on the direct study of galaxies, planets, stars and other celestial objects.

They record data about the observable universe by making use of instruments such as spacecraft or telescopes so that they can answer questions about the universe.

Astronomy doesn’t take the universe as a whole, as cosmology does.

Therefore, astronomers won’t try to study the lifetime of the universe. They will study snapshots of celestial bodies during various evolution stages to try to discover how they were formed, how they evolved, and how they died, as Space explains.

Astronomy has many different subfields, of which cosmetology is just one. These subfields include:

Planetary Astronomy

As its name suggests, this type of astronomy includes studying the growth, evolution, and death of the planets in the universe. Most planetary astronomers will analyze the planets inside the solar system.

Stellar Astronomy

This is astronomy that’s all about the stars! But it also includes nebulae, white dwarfs, supernova, and black holes. Basically, stellar astronomy looks at the chemical and physical processes that occur in our universe.

Solar Astronomy

This is focused on the sun, as its name suggests. Astronomers concentrate on how the quality and quantity of the light that radiates from the sun varies, and this knowledge helps scientists learn how other stars work and how Earth is affected by the sun.  

Galactic Astronomy

This subfield of astronomy is all about studying the Milky Way.

Extragalactic Astronomy

This type of astronomy is about figuring out how star collections form, evolve, and then die to better understand the history of our galaxy.


This is the oldest subfield of astronomy. It measures the planets, moon, and sun. By calculating how they move, scientists can create models of the planets and stars, as well as their birth and evolution. This also enables them to predict events such as eclipses. 

What Is Cosmology?

Cosmology, on the other hand, focuses on the nature of the universe itself, as Ask A Physicist reports. It goes all the way back to the Big Bang and its current state, and it also focuses on the ultimate fate of the universe.

While cosmology concentrates on the universe as a whole, astronomy concentrates on individual celestial objects.

To provide a bit more detail, cosmology strives to answer questions such as the following:

What came before the Big Bang?

We always view the Big Bang as the start of all time and space, but there are speculations about other universes that could possibly exist.

This, of course, is impossible to study in a practical way but it’s exciting to ponder it! 

Where did the Big Bang occur?

It’s a misconception to think that the Big Bang occurred at a single point. It was actually the appearance of time and space throughout the universe, all at once, as Space reports. Mind-boggling?

You bet. 

How old is the universe?

European Space Agency Mission Plack has found that the universe is approximately 13.8 billion years old!

By studying patterns across the sky, Planck was able to learn information about what was happening on the smallest of scales in the moments after the universe was born, as NASA reports, which is pretty incredible.

How, and will, the universe end?

Cosmology looks at the questions of if, and how, the universe will end and it knows that the world’s density plays a crucial role in the universe’s fate.

Basically, scientists have a critical density measurement for the universe and if the universe’s density becomes larger than their calculation the universe will stop expanding and reverse until it eventually collapses.

Did the stars or galaxy come first?

This is an interesting question that cosmology looks at answering. After the Big Bang, the universe was made up of hydrogen and a bit of helium.

Thanks to gravity, the hydrogen collapsed and formed structures, as Space reports. But it’s unknown whether individual stars were created and then these formed galaxies, or if the galaxies formed were present first and then they created stars.

What About Astrophysics?

Now that you know more about astrology and cosmology, you might be wondering where astrophysics fits in. Here’s what you need to know about it and its connection to astronomy and cosmology.

What Is Astrophysics?

Astrophysics is basically like the sibling of astronomy and cosmology! It uses laws of chemistry and physics in order to understand the birth, evolution, and death of celestial objects in space, such as planets, stars, and nebulae.

As you can see, there are already clear similarities between them so things can become a bit complicated.

To make things simple, consider this: the types of questions that astrophysicists strive to answer include things like, “How did we get here?,” “How does the universe work?,” and “Are we alone or is there other life in the universe?”

Astrophysicists use data that’s been gathered by astronomers to understand the universe. While astronomists ask “What?” and “Where?”, astrophysicists will ask questions such as “How?” and “Why?,” as EarthSky reports.

Astrophysics deals with the physics of the universe and this also includes the physical properties of space objects, such as their density, temperature, luminosity, and chemical composition.

How Is Astrophysics Connected To Astronomy And Cosmology?

There are quite blurry lines when it comes to defining astrophysics, astronomy, and cosmology because they are meant to work together. Astrophysics is a branch of astronomy.

To see how astrophysics, astronomy, and cosmology are all connected, let’s look at this example of how they will work together in reality.

Imagine that an astronomer works hard to collect information about a planet.

He or she will need to think like an astrophysicist to use the laws of physics in order to interpret how the planet produces energy, how it moves through space, and to learn more information about it.

Then, astrophysicists will step in to ask questions such as how that planet fits into the universe. Finally, a cosmologist will want to discover how the knowledge about that planet makes sense with the knowledge of the entire universe.

It’s worth mentioning that one person could be all three professions – the astronomer, astrophysicist, and cosmologist!

Related Questions

What is the difference between cosmology and cosmogony?

Cosmology studies the structure and changes in the universe at present, while cosmogony concentrates on how the universe originated, as NASA reports.

What is astrobiology?

Astrobiology encompasses biology, geology, and astronomy. It concentrates on the nature, existence, as well as search for extraterrestrial life, as Britannica reports.


Although you might have thought that astronomy and cosmology were one and the same, it’s clear to see after reading this article that they’re quite different even though they are related.

Astronomy, cosmology, and astrophysics help us to better understand the world in which we live while also helping us to better understand our place in something greater than ourselves.

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