Are the Galxies Expanding?

[Jackalope]

Except objects in our local galaxy.  Those are moving away or towards depending on their relative motion due to gravity.  Other galaxies not gravitationally interacting with our galaxy, sure.

"Unless a collection  of bodies are all  red-shifted."

Red shifted galactic stellar clusters are not. None of them. I can't help it if you're imprecise.

[polymath257]

Red shifting is just the doppler effect-- if a star is moving away, its spectrographic spikes shift toward red.  It doesn't necessarily imply a general expansion, unless a collection of bodies are ALL red-shifted-- which they mostly are.  Pretty much everything we observe seems to be red-shifted.

Not true. Other *galaxies* tend to be red shifted. But the *stars* in our own galaxy can be either red or blue shifted. Most of what you see if you go out and look at the night sky, even with a good amateur telescope, will be stars in our galaxy.

Yes, there is an overall expansion of the universe at large. But 'at large' means galaxies that are over 5 million light years away (and we know of galaxies that are billions of light years away). But there are only three other galaxies that can be seen without a telescope: the Andromeda spiral, and the Large and Small Magellanic Clouds. All of these are gravitationally bound to our own and the Andromeda is *blue* shifted because it is approaching us.

Our own galaxy is about 100,000 light years across. The stars in it orbit the center and we know of stars that are approaching (blue shift). Sirius is one of them. There is an old claim of it being red shifted, but that goes back to the 1800's and the instruments weren't so accurate then. The measurements are also delicate and easy to mess up.

So, no, Sirius is NOT red shifted, no, a red shift for stars in our galaxy is NOT part of the universal expansion, and no, Not all galaxies are red shifted.

[brewer]

So what are those that are brown shifted?

[AFTT47]

Rhonda, all stars orbit the galactic core, just as all the planets in the solar system orbit the sun.

Think of how it works in the solar system. The inner planets orbit faster than the outer planets so none of the planets are orbiting at the same speed. At all times, any of the other planets are either getting closer to Earth or moving further away. The solar system is not expanding or contracting but all bodies are in motion around the sun.

[bennyboy]

So, no, Sirius is NOT red shifted, no, a red shift for stars in our galaxy is NOT part of the universal expansion, and no, Not all galaxies are red shifted.

Eh?

I'm not sure who you're responding to, but I never said any of the things you're saying "no" to me about.

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So what are those that are brown shifted?

That just means someone's been using your telescopes beyond their recommended usage.

[Gawdzilla Sama]

Hey! Proctologists have their dreams!

[polymath257]

So, no, Sirius is NOT red shifted, no, a red shift for stars in our galaxy is NOT part of the universal expansion, and no, Not all galaxies are red shifted.

Eh?

I'm not sure who you're responding to, but I never said any of the things you're saying "no" to me about.

 
I was mainly noting that most of the things we see are NOT red shifted. Distant galaxies are, but closer stars need not be.

[Gawdzilla Sama]

Eh?

I'm not sure who you're responding to, but I never said any of the things you're saying "no" to me about.

 
I was mainly noting that most of the things we see are NOT red shifted. Distant galaxies are, but closer stars need not be.

Anybody with a Ph.D. in orbital mechanics would be able to sort this all out in jig time.

[bennyboy]

I was mainly noting that most of the things we see are NOT red shifted. Distant galaxies are, but closer stars need not be.

I'd bet they are, but you'd have to know where they fit in to the grand scheme of things to determine that.

Let's say a nearby galaxy's center is stationary relative to ours. Blue shifted stars would be in an arm moving toward us, and red in those moving away from us.

Now let's say that galaxy is moving away from us, but less quickly than the negative vector contributed by the movement of that arm. It would appear blue shifted, but less so than it would have been if its galactic center were stationary. Even though it's blue shifted-- it's red shifted.

[Gawdzilla Sama]

Good grief, do we not Google at all? https://en.wikipedia.org/wiki/Stellar_kinematics