What do galaxies orbit?

The stars in the Constellations are all in our galaxy (and a rather small part of our Galaxy at that). You can not see individual stars in any other Galaxy... any other Galaxy that you can see (and there are a few) appear as just a smudge in the sky.

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This will give you an idea of the structure of the universe. You can zoom in or out to see more detail: Atlas of the Universe
IMO, it looks very much like the strings of dough in over-risen bread: voids are free to expand but matter is tied together by gravity.

I don't know that galaxies and clusters actually orbit anything, but they do have a measurable velocity relative to other celestial objects. Therefore they must follow curved paths determined by the local distortion of space caused by all of the mass within range (including dark matter). If there is a large enough concentration of mass, the path will be an orbit. It looks to me as if super-clusters are evenly distributed on the largest scales of the universe with no point of mass concentration that could be a center of rotation.

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littlek wrote:

Rosborne - so, the stars in the constellations - are they all orbiting in gallaxies?

All the stars visible to the naked eye are in our galaxy.

Other galaxies just look like smudges in the night sky.

littlek wrote:

So, the idea of open clusters would help aperson see that not all stars are in orbiting gallaxies?

All stars that we know of are inside galaxies. Open clusters are inside galaxies and so are globular clusters.

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littlek wrote:

Hmmm... from wiki: An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud, and are still loosely gravitationally bound to each other. In contrast, globular clusters are very tightly bound by gravity. Open clusters are found only in spiral and irregular galaxies, in which active star formation is occurring.

Sounds like the open clusters are part of galaxies.

Yes.

I use the program sold here: http://www.starrynight.com

It's fantastic. Smile

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Neat video I ran across a few nights ago, kinda ties in with this topic and others that have been posted of late in this forum.

http://www.youtube.com/watch?v=mcBV-cXVWFw

It has the Numa Numa guy in it...he used that to make a point...it will stop and he gets back to the sky.

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ahhhhhh, of course! thanks all.

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rosborne979 wrote:

I use the program sold here: http://www.starrynight.com

It's fantastic.

I agree - I've been a big fan of Starry Nights for years. Something really neat about it is that it can be integrated with the SETi@Home program, allowing yoiu to "see" on your monitor the area from which the signals from a work unit emanated, and it can be used to drive a 'puter-controlled telescope, allowing you to actually see the region - often even the exact individual celetial body. Super kewel.

As long as you ain't too bothered by the skeeters while you're out there in the boonies looking at the stars - some nights around here, it just ain't worth it Rolling Eyes

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timberlandko wrote:

rosborne979 wrote:
I use the program sold here: http://www.starrynight.com

It's fantastic.

I agree - I've been a big fan of Starry Nights for years. Something really neat about it is that it can be integrated with the SETi@Home program, allowing yoiu to "see" on your monitor the area from which the signals from a work unit emanated, and it can be used to drive a 'puter-controlled telescope, allowing you to actually see the region - often even the exact individual celetial body. Super kewel.

Have you tried using the "Go There" function to just jump from galaxy to galaxy. I'm amazed at how deep you can go into the program and still get real images of cataloged galaxies.

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Oh, you betchya - "Go There" is really neat - and it works when directing a 'scope drive, too.

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Yea, I was pretty sure that all stars are a part of a galaxy.

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rosborne979 wrote:

I use the program sold here: http://www.starrynight.com

It's fantastic.

I need free stuff!

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I once had a free version which showed the night sky from any set of coordinates you plugged in.....

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aperson wrote:

rosborne979 wrote:

I use the program sold here: http://www.starrynight.com

It's fantastic.

I need free stuff!

Science is an area with lots of great Open Source (and free *) software

A few years back I played with a package that showed the sky for any given time that seemed pretty good. Unfortunately I can't remember the name and my quick google search didn't reveal anything.

The most popular seems to be Stellarium which on first glance also good.

[* An unrelated aside-- there is a problem in the "free software" movement that in English, there is no way to distinguish between "Free Speech" and "Free Beer". The term free in free software primarily has the meaning of Free Speech... but in many cases (like this one apparently ) it is Free beer as well.]

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I'm in favour of free beer. Where do I sign?

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For once, spendi, I'm wholeheartedly, unreservedly with you on a proposition. I s'pose it hadda happen sometime.

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This thread is useful for me. I have an early science background, but never took astronomy. Well, first of all, I don't see stars, or few stars.. I've odd eyes, learned I always have had, and never have known, these years, what other people were going on about. Two good friends loved astronomy and, I could not have cared.... less.

I remember being with a friend coming back to LA from Mammoth from skiing trip, and having her then old porsche break down twice in the desert long after midnight. Trucks didn't stop when we waved. (how ugly were we? not so.)

She kept mentioning the stars. What stars? That was one of my clues I was different. Eventually we tried to sleep in the car, brrrrrr.

Luckily, some guys had noticed us/her car, perhaps in reverse order, at some truckstop type diner place, and stopped to help, got us a tow truck from Mojave.

So, since even as a child I didn't know wtf people were saying about a big dipper, I never got all that interested.
As an adult, I might just like a site that will show some of this to me on my computer monitor.
Thanks, y'all.
(not to worry anyone, I see fine in the daytime).

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timber wrote-

Quote:

For once, spendi, I'm wholeheartedly, unreservedly with you on a proposition. I s'pose it hadda happen sometime.

Yeah. It's when you get down to the basic philosophy. Cut all this sophistical shite out.

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Osso- try the adagio from Mahler's 5th. You can hear it on that.

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That was a great link showing super clusters, clusters down to the Solar System.

There are alot of great astro photographs here

http://gallery.rcopticalsystems.com/index.html

PS

Not all stars I presume are gravitationally bound, but I guess the majority are, as they tend to be created in great clouds of atomic dust, meaning they aren't likely to be created in groups of one!

PPS

Astro imaging is a fun but high talent, moderate to high cost pursuit.

At a minimum you could start around $3,000, but you easily spend $30,000 for a more than reasonable set-up. The photos taken on the above link are likely to be done on $80,000 equipment, taking many hours to multiple nights to get all the light, and a day or two to process the image in over 200 ways!

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rosbourne noted this on page two of this thread but he used a bigger word than I will. But that is a nice word. I like it Very Happy

. "Barycenter", pure poetry Very Happy

Any two objects, be they galaxies or dust motes, if they are gravitationally bound, will orbit the center of their masses.

One never orbits around the other. Consequently if the masses are very different as in the Earth-Sun combination the center of the masses will always be very close to the center of the sun and it will appear to a casual observer that we go around the sun.

Now lets take two larger solid (for clarity) masses of equal weight Confused

If they are gravitationally bound each will travel an orbit around the center of the masses which will be between them.

Do you see how this makes it possible to have a galactic cluster or a local group with nothing in the middle Question

Each galaxy is orbiting around the center of mass of the cluster or group of which it is a part . There need be no mass in the center Exclamation

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What do galaxies orbit?

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