From our tiny vantage point on Earth, it’s hard to fathom that the universe extends billions of light-years in every direction. Ever since we first looked to the stars, curiosity has led us to try to understand how many planets, nebulae, stars, galaxies, and more are out there. In this article, we look at how many galaxies are in the universe.
What Is a Galaxy?
A galaxy is a cluster of stars, gasses, dust, and dark matter. A single galaxy can have upwards of 100 to 400 billion stars within, all swirling around a central point. They are held together by gravitational forces, but objects within galaxies often interact with each other as well.
Galaxies vary immensely in size, but the average galaxy is still over 50,000 light-years across. It makes sense that much of the light we see from these objects comes from stars, but a majority of a galaxy’s mass comes from dark matter that we cannot see.
What Types of Galaxies Are There?
All galaxies are categorized into one of four different types: spiral, elliptical, lenticular, and irregular.
Spiral
Spiral galaxies are so-called because of the spiral-shaped tendrils that stretch out from their centers. Sometimes these spirals are tightly bound, while other times they are much less compact.
Elliptical
Elliptical galaxies also get their name from their shape. These celestial objects fit the form of an egg, but some are long and thin while others are nearly spherical.
Lenticular
Lenticular galaxies resemble a lens on a magnifying glass. They are thin and circular in shape but lack the arms that spiral galaxies have.
Irregular
As you can probably imagine, irregular galaxies are those that don’t fit into the mold of the other two categories. These galaxies tend to be relatively small compared to others and don’t have a defined shape. Due to their size, some irregular galaxies actually orbit spiral or elliptical ones.
What’s at the Center of a Galaxy?
For many years, scientists could only speculate about what was at the center of these massive swirling groups of stars. Common theories pointed to a mysterious black hole, but no one was able to prove it.
It wasn’t until 1974 that a radio source was discovered at the center of our galaxy, linking even more evidence to black holes. Finally, in the early 2000s, observations of stars near the galaxy’s center provided enough evidence to confirm the existence of a black hole.
In fact, our galaxy has a supermassive black hole at its center, roughly four million times the mass of our own Sun – and not a whole lot larger. Due to its proximity to the constellation, the black hole was dubbed Sagittarius A*.
Where Are We in This Sea of Stars?
The Earth and the Solar System we’re a part of sit in one of the spirals of the Milky Way Galaxy. The unconventional naming convention stems from a Greek myth about the goddess Hera spraying some milk across the sky.
Other cultures have cooler names for our galaxy. The Chinese call it the “Silver River,” while it’s referred to as the “Backbone of Night” in Southern Africa.
Our Milky Way Galaxy is over 100,000 light-years across. There are upwards of 400 billion stars and 100 billion planetary bodies within this span. It spins at a rate of approximately 136 miles per second (219 kilometers per second) around the supermassive black hole located at its center.
The Discovery of the First Galaxy Outside Our Own
Astronomers have been aware of galaxies for over a thousand years but weren’t actually aware of what they were looking at. In the early 20th century, scientists were finally able to make sense of the distant objects beyond our own galaxy.
With only a rudimentary understanding of our own location within the Milky Way, Edwin Hubble took to studying what he thought were nebulae. During this study, he discovered variable stars within the Andromeda “nebula” and estimated that these stars were over 900,000 light-years away.
At such a distance, there was no way these stars could be part of our own galaxy. Hubble concluded that the object he had been studying was not a nebula but rather another galaxy. It was the first time anyone in human history had measured such a great distance.
How Can We Count Galaxies?
After Hubble’s incredible discovery, the search for what else lies beyond our own Milky Way was on. On Earth, we have to rely on the light from stars in these galaxies to travel through space and reach us. The problem here is that there are many stars even within our own galaxy that are too far or too dim to see.
Even in the vast confines of space, galaxies are so far from Earth that they can be hard to see. Two galaxies near each other can appear as one, and it can be all but impossible to decipher the difference between the two. You must also factor in the light pollution on Earth, even in the most remote parts of the planet. There’s just only so much we can see.
Looking From Beyond Earth
To circumvent at least some of these issues, NASA launched the Hubble Space Telescope back in 1990. This telescope sits 340 miles (547 kilometers) above the Earth’s surface and can see into the depths of space much more clearly than anything on the planet.
With the Sun putting out so much light, scientists wanted to do even better. The New Horizons spacecraft launched in 2006 to visit the furthest reaches of the Solar System. New Horizons is currently some 4,657,000,000 miles (7,495,000,000 kilometers) from Earth and can look out into the cosmos with a much clearer scope.
More recently, the James Webb telescope launched on December 25th, 2021, and will travel away from Earth before looking into the universe. NASA hopes the telescope will be strategically placed to see clearer and further than ever before.
How Many Galaxies Are There?
The simple answer is that no one knows. The universe is estimated to be over 13 billion years old, and we now have the capability to see well over 13 billion light-years into space. However, finding galaxies is in many ways like finding needles in a haystack.
A few years ago, estimates based on data from the Hubble telescope put the universe’s total galaxy count at nearly two trillion. However, more recent data from New Horizon’s scans show that space is much darker than anything the Hubble telescope could see.
New estimations put the number of galaxies in our universe somewhere between 100 and 200 billion. With the James Webb telescope preparing to travel into deep space, it will be interesting to see if its findings confirm or refute these latest numbers.
How Far Is the Nearest Galaxy From Our Own?
Edwin Hubble first confirmed the existence of the Andromeda Galaxy back in the early 1900s. This galaxy is our closest neighbor, but Hubble was wrong about just how far away it was. His estimate of 900,000 light-years turned out to be too close. It turns out the Andromeda Galaxy is actually over 2.5 million light-years away.
This means, even at the speed of light, it would take 2.5 million years to make the trip one way. Whether lucky or not, the Milky Way and Andromeda galaxies are slowly drifting towards each other, making the trip a little less cumbersome.
The two galaxies will meet in approximately 4.5 billion years. Since stars within these clusters are so spread apart, they will likely merge into one super galaxy. It’s unclear what events will take place, but we will add nearly a trillion stars to those that already exist around us.
Galaxy Clusters
Although galaxies are carefully spread out through space, some are obviously closer than others.
Local Groups
Galaxies within five million miles (eight million kilometers) of our Milky Way are considered to be part of our Local Group.
We share this space with two other large galaxies, Andromeda and Triangulum. Also within this space are some 50 dwarf galaxies. These galaxies are gravitationally linked with each other, as indicated by the fact that we are slowly moving toward the larger Andromeda.
Superclusters
Our small Local Group only covers a total of ten million light-years of space. Scientists have discovered that the 50+ galaxies in our Local Group are linked with approximately 100 other groups of galaxies in a supercluster.
Our supercluster is known as the Virgo Supercluster. This group of galaxies covers around 110 million light-years of space. With over 100 Local Groups, there are likely 2000 galaxies within. Even the Virgo Supercluster represents a very small section of the boundless universe we’re a part of.
Is There Anything Between Galaxies?
The area between galaxies is called intergalactic space. This space is a near-perfect vacuum with almost nothing within. There’s very little dust or debris, with an estimated hydrogen atom every meter or so. Considering there are 2.5 million light-years of intergalactic space between the Andromeda Galaxy and us, it sounds like a very dull trip.
Can We See the Milky Way From Earth?
The Earth sits about half way down the Orion spiral arm of the Milky Way. As a result, we can look up into the sky on any given clear night and see the rest of the galaxy unfold before us. Everything we see with the naked eye (apart from the Andromeda Galaxy) is a part of our glorious Milky Way.
The Orion arm is represented by a band of light that can be seen from Earth in areas with minimal amounts of light pollution. This band stands out as we are looking directly into the plane of the central disc of our galaxy. This band makes for a fantastic photo opportunity if you can find a dark enough location.
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What is the Biggest Galaxy?
Of all the space we’ve been able to search through, scientists have discovered one galaxy that stands out among the others.
Galaxy IC 1101 is over five million light-years across at its longest point and contains an estimated 100 trillion stars. Compared to the Milky Way, IC 1101 is 50 times larger, with nearly 1000 times more stars within.
The elliptical galaxy is located in the constellation Virgo and exists just over one billion light-years from Earth. The massive cluster is likely the result of the merging of several galaxies over a long period of time. Many stars within are billions of years older than our Sun, potentially indicating that the galaxy is no longer creating stars and will eventually fade away.
Are There Planets in Other Galaxies?
Stars and the galaxies they are a part of are easier to detect because they give off visible light that we can see from Earth. On the other hand, planets are much harder to locate as they have no light source of their own.
That being said, scientists believe they have discovered an alien world in another galaxy for the first time. Within the Whirlpool Galaxy, some 23 million light-years from Earth, astronomers detected an object orbiting a pair of stars. Tatooine, anyone?
While monitoring X-rays for the binary star system, there was a three-hour period of time when something blocked these signals from view. Due to its transit time, scientists believe the object is the size of Saturn. This was a lucky break, as the planet could take another 70 years before it returns to this position.
Final Thoughts
It’s mind-boggling to think about just how enormous our universe is. Even our supercluster of 2000 galaxies covers only the tiniest fraction of known space. Modern technology has only allowed us to estimate the number of galaxies out there, and this number seems to change every time we look.
Even at 2.5 million light-years away, it’s incredible to think that we can see the Andromeda Galaxy with the naked eye. With a bit of magnification, you can snap some incredible pictures of this galaxy all on your own.