Spiral Galaxies: 3 Distinguishing Characteristics

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In summary, spiral galaxies are disk-shaped with a bulge at the center, and arms. They vary in size and are typically found outside of clusters. They can have spiral arms, a bar, and/or a bulge.
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zcapa14
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What are three distinguishing characteristics that can differ among spiral galaxies?
 
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  • #2
the arms? i think is one.
 
  • #3
i would guess that its disklike structure, with the buldge at the center, and arms .
 
  • #4
The best know classification scheme is the Hubble system. It establishes two basic types - regular and barred - and three subclasses of each type based on how tightly the arms are wrapped. The de Vaucouleurs classification system is a more detailed version of the Hubble scheme which profiles spirals 3 dimensionally. The DDO, or van den Bergh scheme factors luminosity into the mix and the Yerkes, or Morgan system factors in the integrated spectrum. For an overview see:
http://www.astro.ufl.edu/~vicki/Lecture2.pdf .
Of course there are other systems at well, but these are the most widely used.
 
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Welcome to Physics Forums zcapa14!

Just a friendly word of advice - please read the guidelines (and note that duplicate posts are not welcome here).
 
  • #6
zcapa14 said:
What are three distinguishing characteristics that can differ among spiral galaxies?

If you mean things that distinguish them from ellipticals, then there are a lot:

1. They have disks with organized rotation.
2. They have a lot of gas and dust.
3. They have active star formation.
4. They're bluer (consequence of #3).
5. They can have spiral arms (density waves).
6. They're more common outside of clusters.
7. They sometimes have bulges.
8. They sometimes have bars.

From one spiral to another, the following things are known to vary and can be used to classify them:

1. The size of the bulge.
2. Whether or not there's a bar.
3. The number of spiral arms.
4. The continuity of the spiral arms.
5. The angle about which the arms wrap.
6. How blue they are (rough measure of amount of star formation)
7. Amount of gas and dust.

There are other things, but those can all be visually apparent. You can also measure rotation curves, ellipticities, etc.
 

Related to Spiral Galaxies: 3 Distinguishing Characteristics

1. What are spiral galaxies?

Spiral galaxies are a type of galaxy characterized by a distinct spiral shape, with arms of stars and interstellar matter swirling around a central bulge. They are one of the three main types of galaxies, along with elliptical and irregular galaxies.

2. What are the distinguishing characteristics of spiral galaxies?

The three main distinguishing characteristics of spiral galaxies are their spiral structure, their central bulge, and their disk-like shape. The spiral arms are made up of young, bright stars and gas, while the central bulge is typically composed of older stars. The disk of a spiral galaxy also contains a large amount of gas and dust, which can form new stars.

3. How do spiral galaxies form?

The exact process of spiral galaxy formation is still not fully understood, but it is believed that they form from the gravitational collapse of a large cloud of gas and dust. As the cloud collapses, it begins to spin, creating a disk-like shape. The spiral arms then form as a result of density waves within the disk, causing matter to clump together and form stars.

4. Can spiral galaxies evolve into other types of galaxies?

It is possible for spiral galaxies to evolve into other types of galaxies over time. For example, as a spiral galaxy ages, it may merge with other galaxies, altering its shape and potentially becoming an elliptical galaxy. Additionally, the gas and dust in a spiral galaxy may eventually be depleted, leading to a decrease in star formation and a potential transformation into an elliptical galaxy.

5. Are there different types of spiral galaxies?

Yes, there are several subtypes of spiral galaxies, including barred spirals, which have a bar-shaped structure in the center, and grand design spirals, which have two well-defined spiral arms. There are also intermediate spiral galaxies, which have characteristics of both spiral and barred spiral galaxies. These subtypes may provide clues about the formation and evolution of spiral galaxies.

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