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what type of galaxy is milky way
The Milky Way Galaxy
Our Sun (a star) and all the planets around it are part of a galaxy known as the Milky Way Galaxy. A galaxy is a large group of stars, gas, and dust bound together by gravity.
They come in a variety of shapes and sizes. The Milky Way is a large barred spiral galaxy.
All the stars we see in the night sky are in our own Milky Way Galaxy.
Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area.
Tell me more about galaxies
It is very difficult to count the number of stars in the Milky Way from our position inside the galaxy. Our best estimates tell us that the Milky Way is made up of approximately 100 billion stars.
These stars form a large disk whose diameter is about 100,000 light years. Our Solar System is about 25,000 light years away from the center of our galaxy â€“ we live in the suburbs of our galaxy.
It takes 250 million years for our Sun and the solar system to go all the way around the center of the Milky Way.
Read a NASA Blueshift blog post about how many stars there are in the Milky Way
We can only take pictures of the Milky Way from inside the galaxy, which means we don’t have an image of the Milky Way as a whole.
Why do we think it is a barred spiral galaxy, then? There are several clues.
The first clue to the shape of the Milky Way comes from the bright band of stars that stretches across the sky (and, as mentioned above, is how the Milky Way got its name).
This band of stars can be seen with the naked eye in places with dark night skies.
That band comes from seeing the disk of stars that forms the Milky Way from inside the disk, and tells us that our galaxy is basically flat.
Several different telescopes
both on the ground and in space, have taken images of the disk of the Milky Way by taking a series of pictures in different directions.
– a bit like taking a panoramic picture with your camera or phone. The concentration of stars in a band adds to the evidence that the Milky Way is a spiral galaxy.
If we lived in an elliptical galaxy, we would see the stars of our galaxy spread out all around the sky, not in a single band.
Another clue comes when astronomers map young
bright stars and clouds of ionized hydrogen in the Milky Way’s disk. These clouds, called HII regions, are ionized by young, hot stars and are basically free protons and electrons.
These are both important marker of spiral arms in other spiral galaxies we see, so mapping them in our own galaxy can give a clue about the spiral nature of the Milky Way.
There are bright enough that we can see them through the disk of our galaxy, except where the region at the center of our galaxy gets in the way.
There has been some debate over the years as to whether the Milky Way has two spiral arms or four.
The latest data shows that it has four arms, as shown in the artist’s illustration below.
Additional clues to the spiral nature of the Milky Way come from a variety of other properties
Astronomers measure the amount of dust in the Milky Way and the dominant colors of the light we see, and they match those we find in other typical spiral galaxies.
All of this adds up to give us a picture of the Milky Way, even though we can’t get outside to see the whole thing.
There are billions of other galaxies in the Universe
Only three galaxies outside our own Milky Way Galaxy can be seen without a telescope, and appear as fuzzy patches in the sky with the naked eye.
The closest galaxies that we can see without a telescope are the Large and Small Magellanic Clouds. Even they are about 160,000 light years from us.
It is about 2.5 million light years away from us, but its getting closer, and researchers predict that in about 4 billion years it will collide with the Milky Way.
, i.e., it takes light 2.5 million years to reach us from one of our “nearby” galaxies.
Some galaxies are similar to the Milky Way, but some are quite different.
Galaxies are sprawling systems of dust, gas, dark matter, and anywhere from a million to a trillion stars that are held together by gravity.
Nearly all large galaxies are thought to also contain supermassive black holes at their centers.
In our own galaxy, the Milky Way, the sun is just one of about 100 to 400 billion stars that spin around Sagittarius A*,
a supermassive black hole that contains as much mass as four million suns.
The deeper we look into the cosmos, the more galaxies we see. One 2016 study estimated that the observable universe contains two trillion.
—or two million million—galaxies. Some of those distant systems are similar to our own Milky Way galaxy, while others are quite different.
Types of galaxies
Before the 20th century, we didn’t know that galaxies other than the Milky Way existed; earlier astronomers had classified them as as “nebulae,”
since they looked like fuzzy clouds. But in the 1920s, astronomer Edwin Hubble showed that the Andromeda “nebula” was a galaxy in its own right.
Since it is so far from us, it takes light from Andromeda more than 2.5 million years to bridge the gap. Despite the immense distance, Andromeda is the closest large galaxy to our Milky Way.
and it’s bright enough in the night sky that it’s visible to the naked eye in the Northern Hemisphere.
In 1936, Hubble debuted a way to classify galaxies, grouping them into four main types: spiral galaxies, lenticular galaxies, elliptical galaxies, and irregular galaxies.
More than two-thirds of all observed galaxies are spiral galaxies
A spiral galaxy has a flat, spinning disk with a central bulge surrounded by spiral arms.
That spinning motion, at speeds of hundreds of kilometers a second, may cause matter in the disk to take on a distinctive spiral shape, like a cosmic pinwheel.
Our Milky Way, like other spiral galaxies, has a linear, starry bar at its center.
Elliptical galaxies are shaped as their name suggests: They are generally round but can stretch longer along one axis than along the other, so much so that some take on a cigar-like appearance.
The universe’s largest-known galaxies—giant elliptical galaxies—can contain up to a trillion stars and span two million light-years across.
Elliptical galaxies may also be small, in which case they are called dwarf elliptical galaxies.
The Milky Way[a] is the galaxy that includes the Solar System, with the name describing the galaxy’s appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term Milky Way is a translation of the Latin via lactea, from the Greek γαλακτικός κύκλος (galaktikos kýklos), meaning “milky circle.
- RESOURCE: WIKIPEDIA