Milky Way galaxy illuminating the night sky above a canyon. Milky Way galaxy illuminating the night sky above a canyon.

The Study of the Milky Way Galaxy and its Structure

I’m sure you know a bit about the Milky Way. And why not? We all have read a lot about it in schools. However, the concept is itself so intriguing that it not only fascinates me or an avid reader like you but it has engaged many researchers and scientists for years.

The Milky Way is the galaxy that constitutes our solar system. It’s a misty band of light that can be seen in the sky at night, formed from stars that the naked eye cannot individually distinguish.  Just as planets in our solar system revolve around the sun, the solar system orbits the center of the Milky Way.

In this article, I’ll tell you about the structure of the Milky Way galaxy, how it moves, and more.

Why is Our Galaxy Called the Milky Way Galaxy?

Our galaxy in space is named the Milky Way because it resembles a milky band across the night sky. I’ll tell you a surprising fact- Greek stories say it was created when the goddess Hera sprayed milk across the sky.

You will also be surprised to know that different places call the Milky Way by different names. in China, it’s known as the “Silver River,” and in the Kalahari Desert in South Africa, it’s called the “Backbone of Night.”

Let Me Tell You About Its Structure and Composition

The Milky Way is a big spiral with different parts: the center, middle, and even spiral arms. It has an outer space area plus a flat part.

  • The nucleus is the central part. It is small and has a black hole plus some other stars. But it is pretty far from actually affecting us directly.
  • Next, there’s the middle part, called the central bulge. It’s a round group of stars in the middle, like a dense swarm, mostly old stars, gas, and dust.
  • Then, there’s the flat part called the disk. It’s like a thin pancake of stars and gas going around the center. The Milky Way’s galactic disk is really big, about 100,000 light-years across. This is where the spiral arms are, and it’s also where new star formation happens.
  • Spiral arms are like curved arms that make the Milky Way look like a pinwheel, and these arms have a lot of gas, dust, and young blue stars. It is always spinning, so these arms are moving through space, and our solar system is on this ride, going at a super fast speed.
  • Finally, there’s the outer part called the halo. It’s like the retirement area of the galaxy, with old stars and clusters. There’s also something called “dark matter” in the halo, which we can’t see but can feel its pull.

So, the Milky Way is like a giant barred spiral galaxy with a center, middle, flat part, arms, and outer space retirement area.

Do You Know How Stars Move?

All the stars and dust in the disk move at about the same speed. This means that stars inside the Sun’s path go around the center faster than we do, while stars outside go around slower. Our galaxy isn’t like a spinning CD or DVD where different parts move at different speeds but finish spinning at the same time.

In our galaxy, stars in the disk all go at almost the same speed. So, stars near the edge take longer to go around because they have more distance to cover. The spiral arms in our galaxy might be like ripples in water when you drop a stone. These spiral arms have more stuff like gas, dust, and stars, and that’s where new stars are born.

What is our Galaxy Made Up Of? I’ll Tell You More Interesting Details

1. Black Hole

A big black hole is in the middle of the Milky Way Galaxy, and we call this area Sagittarius A* (pronounced “A star”). The black hole itself is hard to see because it doesn’t give off any light, and there’s a lot of gas and dust in the way. You can’t see the black hole directly because the stars near Sagittarius A* move super fast.

Black Hole moving in front of the Milky Way background

Astronomers figured out that this black hole must be really, really heavy—at least 3.7 million times heavier than our sun.

2. Other Constituents of Galaxy

Scientists think that only around 10% of the stuff in our galaxy comes from stars, gas, and dust. They believe there has to be more stuff that we can’t see because of how the galaxy spins. If all the stars were going around a big thing in the middle, like how planets orbit the Sun in our Solar System, the stars near the edge should move slower.

This is like how outer planets move slower than inner ones. But in our galaxy, stars at the edge go almost as fast as stars near the center.

The Study of the Milky Way Galaxy and its Structure
Image by Pexels from Pixabay

To explain this, there must be more stuff in the galaxy than we can see. Scientists guess that this extra stuff is dark matter; you can’t see it, it doesn’t give off any light, and they haven’t found it yet.

And Yes a Few Neighbors!

The Milky Way Galaxy is part of a group of more than 30 galaxies called the Local Group, and the biggest one in the group is the Andromeda Galaxy, whereas the third largest is the Triangulum Galaxy. The rest are smaller, like dwarf spheroidal and dwarf elliptical galaxies and other spiral galaxies.

Our Local Group is part of a much bigger group called the Virgo Supercluster. It has over 100 galaxies and clusters and is really huge, over 100 million light-years across.

Our supercluster is moving at about 600 kilometers per second toward a very big supercluster called the Great Attractor. Usually, these globular clusters aren’t held together by gravity and are moving away from each other because the universe is expanding.

The Study of the Milky Way Galaxy and its Structure
Photo by Bryan Goff on Unsplash

When you look at the night sky from Earth, it looks like a faint strip of light made up of numerous stars that you can’t see separately.

Long ago, people thought the Milky Way had all the stars in the Universe, but in the 1920s, astronomers found out, through a big discussion, that the Milky Way is just one of many galaxies. Edwin Hubble’s observations helped us understand that many other galaxies are out there, too.

Last Updated on May 19, 2024 by Pragya


Anushree Khandelwal
  1. Anushree Khandelwal’s exploration of the Milky Way’s structure is a concise yet comprehensive guide, providing insights into its nomenclature, composition, motion, and neighboring galaxies. The article elegantly simplifies complex astronomical concepts, making it accessible for readers with varying levels of expertise. The inclusion of historical perceptions and scientific advancements adds depth to the narrative, making it an engaging and enlightening read. I learn many new things after reading it.

  2. I initially thought that this article was suited for readers with a high level of expertise but I was surprised to find the I could easily understand it. I gained lot of new knowledge about Milky ways and our neighbouring galaxies. Thank you for the research and efforts.

  3. Anushree your Milky Way guide was surprisingly easy to understand, even for someone like me. I learned a lot about its structure and neighboring galaxies. Thanks for making complex stuff simple!

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