In our Universe, there are over 100 billion galaxies, and our Milky Way galaxy is just one of them. Galaxies come in four different types, the one we live in is a spiral barred type of galaxy.
The Milky Way is basically a collection of gas, dust, and stars that spread for around 100,000 light-years across, but it is also several thousand light-years thick.
Every star we see in the night sky with the naked eye is part of the Milky Way galaxy; however, the Andromeda galaxy is also visible to the naked eye. With that being said, here are some interesting facts about our awesome galaxy.
Milky Way Galaxy Facts:
1. The Milky Way has an invisible halo
When it comes to our galaxy, about 90% of matter cannot be seen. It is called dark matter, and we have yet to understand its properties. Everything that we can see is luminous matter, and it represents only 10% of the Milky Way.
This dark matter causes an invisible halo that surrounds our galaxy. Its existence has been demonstrated by simulations of how the Milky Way spins. If this dark matter weren’t present, every star would orbit much slower around the galaxy’s center.
Present in this halo, are the globular clusters, which are groups of the most ancient stars in the Universe.
2. Our galaxy has billions of stars in it
Based on our Milky Way’s mass, which is 100 billion times that of the Sun, it is believed that there could be anywhere between 100 to 400 billion stars in our galaxy.
Apart from this, there are around 40 billion exoplanets, which are planets that orbit other stars rather than our Sun, and are similar in size to Earth. However, counting every type of planets such as gas giants, or rogue planets, there could very well be more than 100 billion planets in our galaxy as well.
However, our Milky Way is medium in size based upon these estimations, at least when compared to other galaxies. One of the most massive galaxies ever detected, IC 1101, has over 100 trillion stars.
3. The Milky Way has a supermassive black hole at its center
It has been designated Sagittarius A*, and it is around 4.3 million times more massive than our Sun. Many galaxies have such gargantuan celestial objects at their center [1].
However, it is not the only black hole in our galaxy. There are over 100 million of them scattered throughout the Milky Way, but none are nearly as significant as Sagittarius A*.
One of the biggest recently detected, is near a star designated LB-1, and it is 70 times or more massive than our Sun. Sagittarius A* is around 28,000 light-years away from Earth.
Curious to know more about the black holes? Check 9 Of The Most Surprising Facts About The Black Holes.
4. The Sun takes around 250 million years to orbit around the Milky Way
We have already performed 20 orbits around the galaxy since our Sun was born. Everything in the Milky Way orbits around the galactic center, where the supermassive black hole Sagittarius A* is located. The Milky Way itself is rotating in a clockwise direction.
Though our Sun is young, the Milky Way is about as old as the Universe itself. Some estimates put the age of the Universe at around 13.7 billion years old.
When it comes to the Milky Way, those estimations show that it is around 13.6 billion years old. However, some parts of it formed in the early days of the Universe, like the disk and bulge, which weren’t fully developed until about 10-12 billion years ago.
5. The Milky Way was made from other galaxies
This seems to be the natural process of the Universe. Galaxies merge to form more substantial and more complex galaxies. Such is the case of our galaxy, which seems to be set on a collision course with the Andromeda galaxy. This will occur in just a few billion years [2].
Analyzing the outermost regions of our galaxy, scientists determined that it hasn’t undergone any mergers with other large galaxies in the last 10 billion years. This is unusual for spiral galaxies similar to our own, such as Andromeda, which seems much more active in this process.
However, the Large and Small Magellanic clouds are orbiting the Milky Way, and they are remnants of dwarf galaxies that have been devoured by our own. Another dwarf galaxy, Sagittarius, is on the process of merging with the main body of the Milky Way galaxy.
6. The Milky Way is part of even higher celestial structures
Both the Milky Way and Andromeda are part of a group of 50 tightly bound galaxies known as the Local Group. The Local Group itself is part of an even bigger structure known as the Virgo Supercluster of galaxies.
This supercluster is surrounded by voids that change shape over time, creating filamentous structures of galaxies. When it comes to the Virgo Supercluster, it’s drawn towards the Great Attractor, which in turn forms part of a more magnificent structure named Laniakea.
If you would like to discover more about the space, check 16 Mind-Blowing Space Facts You Should Know.
7. Our galaxy has four major spiral arms
They are sights of intense star formation. We are located in such an arm, though it is a minor one named Orion Arm. The significant arms contain higher densities of interstellar gas, dust, and a greater concentration of star formation [3].
The four considerable arms in Milky Way galaxy are:
- Perseus Arm
- Outer Arm
- Scutum-Centaurus Arm
- Carina-Saggitarius Arm
It is currently unknown how many minor arms our galaxy has.
8. There could be life and plenty of it in our Milky Way
Current estimations reveal the strong possibility of over 40 billion Earth-sized planets being present in our galaxy. They are orbiting Sun-like stars and are positioned in their habitable zones, where life can develop.
This means that there are vast chances that life is present elsewhere in our galaxy; however, we are proof that the Milky Way is at least favorable towards developing life.
9. There isn't actually any photo or illustration of the Milky Way galaxy that is complete
Much of our galaxy still remains unknown, and this isn’t surprising given its vastness and the fact that we have only just begun our journey of observing it.
However, our observations are continuous, and each and every day, plenty of new planets, stars, and other things are revealed, and maybe one day we will have a more complete view of our own galaxy.
10. The ancients knew about the Milky Way
However, they did not know what it was exactly. This all changed when Galileo Galilei pointed his crude telescope in the sky and saw thousands of stars.
After many other observations and studies conducted by various prolific people, we reached a crucial point. For many years, we believed that our galaxy was the entire Universe, surrounded by nebulas.
This changed when an astronomer named Edwin Hubble studied the Andromeda nebula and concluded it was also a galaxy, among many others.
Discover the most important galaxy in space (Hubble Space Telescope): Top Features and Discoveries of Hubble Space Telescope
11. The Milky Way is moving
The galaxy is moving at a velocity of 600 km / 372 mi per second towards a densely packed region of space called the Shapley Attractor. When we take our galaxy’s size in comparison, the accurate speed of movement is actually smaller.
The Shapley Attractor doesn’t just pull the Milky Way; we are also pushed by the Dipole Repeller, an empty void of space.
