Questions tagged [spiral-arms]

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Did the density wave theory for spiral arms take account of this phenomenon?

I came across this link. In it the author speculates that in the outer region of a galaxy, the spiral arms overtake the stars, and vice versa for the inner region. That means there must be a middle ...
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1 vote
2 answers
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Fate of lone spiral galaxies?

I know Hubble's galaxy classification scheme and the bifurcation from elliptical galaxies into two types of spiral ones. I am also aware of different theories on how spiral galaxies form e.g. through ...
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Is there a minimum size for a galaxy to have spiral arms?

Is there a minimum size or mass for a galaxy to present spiral arms? I don't remember many small galaxies with spiral arms. Does the mechanism responsible for producing spiral arms no longer hold if ...
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18 votes
1 answer
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How small can a spiral galaxy be?

The smallest observed spiral galaxies I can find are NGC 2976 and NGC 4605, both with a diameter of 20 kly, but I don't have anything like an exhaustive source to search. I've also found a mention ...
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46 votes
2 answers
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Does the sun cross other spiral arms in its movement around the galaxy's center?

Today, Ansa.it released an article that states: [...]. In questo suo peregrinare galattico, il Sole ha attraversato anche i due bracci della Via Lattea Perseo e Centauro. "Sono zone di alta ...
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4 votes
2 answers
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Are magnetic field lines Spiral for Spiral Galaxies? If no, then how it look like topologically?

I am an undergraduate doing summer project at USO. I am working on Sun's Magnetic field model. I got spiral graph for that, which looks like any spiral Galaxy. Do you think that there is some ...
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2 votes
1 answer
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Relationship between galactic rotation and stellar lifetime

I have read that the lifetime of stars is much less than the period of rotation for a spiral galaxy. For example https://www.coursera.org/learn/evolvinguniverse/lecture/wlYhz/the-origin-of-spiral-arms ...
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4 votes
1 answer
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How is the bar formed in a Barred-Spiral galaxy?

How does the bar in a barred spiral galaxy form? What prevents it from being spirals all the way down like water spiralling down a plughole?
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1 answer
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What are evidences of stationarity of rotation of galaxies

Recently I have found the article Does There Really Exist the Problem of the Dark Matter in Spiral Galaxies? which states that dark matter does not exist because astronomers are wrong assuming ...
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1 answer
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In which direction does the Milky Way rotate?

We don't have a photo of our Milky Way the whole, all the pictures are artists' interpretations showing a bulge, a central bar, and several spiral arms. The milky way is spinning. I would like to know:...
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3 votes
1 answer
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Have parameters been determined for the Fourier components of a Milky Way spiral density-potential model?

Spiral arms in galaxies can be modeled by potentials of the form $$\Phi_{\text{spiral}}(R,\theta,z,t)=\sum_mA_m(R,z)\cos(m\theta-m\theta_0-\phi_m(R)-\Omega_pt)$$ where $A_m(R,z)$ is the $m$th-order ...
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Do we know if we are overtaking or falling behind our arm?

Here's our galaxy as best we know, courtesy of this Wikipedia article: It seems that as best we know, each arm is a compressed or brighter area (rather like a wave). Looking at that image, do we ...
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