Star Positions?

[davewaldo]

Hi Everyone,

I post this here as its a pretty basic question, but one that interests me.

When looking through a scope, or indeed just looking up to the sky, I'm trying to understand the placement (distance) of stars.

I'm guessing that most of the stars we see are from our own galaxy, and we are looking through these stars to distant galaxies and other objects.

Are there many lone stars floating in between or are stars generally contained within galaxies? (this is the model I'm leaning towards)

Or is there a wide disbursement of stars throughout the universe with galaxies also dotted around?

Just trying to get a vision of how our universe is built.

Any info on this topic would be appreciated.

Cheers,

Dave.

[Blue Skies (Jacquie)]

As far as I know nearly all stars we know about are contained within galaxies or globular clusters. Just about all the individual stars you see looking up at night are within a couple of thousand light years. There are always exceptions, of course, but you can be pretty safe in saying we're just seeing the local neighbourhood. So we are looking through these stars to see the galaxies beyond.

As for intergalactic stars, I've read that it is one of the current holy grails, to be the first to find a star floating about between galaxies. It's thought they must be out there but they haven't been identified yet.

[erick (Eric)]

Just speculating here:-

It makes sense to me that intergalactic stars must be out there. We've seen images of lots of interacting galaxy pairs and even triples with large streamers of stars being flung considerable distances from the galaxies. Surely some of them continue out into intergalactic space?

Are we going to see them? Well not without the really big scopes and the HST, I would expect, given the challenge of seeing individual stars beyond our own galaxy.

Are there individual stars not too far from the Milky Way that could be seen? Don't know, but I don't think the Milky Way has had recent enough encounters with other galaxies to leave lost stars close enough to be observed? Give it a few billion years until we have our close encounter with M31, maybe?

OK, that said, I thought I should google "intergalactical stars" Lots of hits worth reading I would say!

HST has apparently identified 600 lost and lonely stars in part of the Virgo cluster.

Read this from 1997:-

http://hubblesite.org/newscenter/arc...eases/1997/02/

[davewaldo]

mmm very interesting thank you Eric and Jacquie.

Its nice to know these things when observing so I can mentally picture what I'm seeing.

Its incredible to think that all the stars we can see are only in our tiny part of space!

[Starkler (Geoff)]

Originally Posted by davewaldo

Its incredible to think that all the stars we can see are only in our tiny part of space!

Interesting. I wonder how far away the farthest naked eye visible star is?

edit: A couple of minutes googling turned up Hipparcos 5926 (V762) in Cassiopeia at 16,308 light-years away, at magnitude 5.84

[desler]

There are far more knowledgable people on this site to help you on your path.

In the subject of cosmology and the creation of the universe, I have just watched a copy of a BBC Horizon Documentary on Super Massive Black Holes.

When you get rid of all the scifi music and thoughts of impending distruction, the physics, maths and pure discovery is mind boggling.

You also get an insight into Hubble and I think (the Kek) telescope which is amazing.

Various copies of the show are running around on the net, Hopefully you'll enjoy!


Darren

[Ian Robinson]

There are rogue stars in the intergalactic voids , they didn't form there, they will be stars that were ejected by gravitationally disrupted galaxies (who are merging, have merged or have interacted.

[davewaldo]

Very interesting, thank you Darren and Ian.

I'll search for the BBC doco, sounds right up my alley.

[glenc (Glen)]

Dave, here is a good introduction to the universe.
http://www.atlasoftheuniverse.com/

This catalogue contains positions, magnitudes and parallaxes (distances) for millions of stars.
http://vizier.cfa.harvard.edu/viz-bi...?-source=I/280

distance (in light years) = 3.26 / parallax (in arcsecs)
http://en.wikipedia.org/wiki/Parallax

[Chippy (Nick)]

Originally Posted by erick

Just speculating here:-

Are there individual stars not too far from the Milky Way that could be seen? Don't know, but I don't think the Milky Way has had recent enough encounters with other galaxies to leave lost stars close enough to be observed? Give it a few billion years until we have our close encounter with M31, maybe?

In fact the milky way has had recent encounters with other galaxies. Several in fact (although recent is a relative term) if I'm correct. The Magellanic stream is the result of one such encounter, and I believe a dwarf is currently being consumed near the galactic centre. It's on the other side, so has only recently been identified as such, due to the difficulty in seeing "through" the galactic centre. It is likely that dozens have been consumed over a longer period. A number of star clusters have been determined to be the likely remains of merged dwarfs based on recent surveys.

From memory I think we are also on schedule to swallow others before the merge with M31 (possibly LMC and SMC I think, but perhaps others). A number of dwarfs have only recently been discovered in the "local group".

[erick (Eric)]

I was thinking of "big" encounters, large enough to toss big streamers of stars into intergalactic space. Not sure if the encounters with dwarf galaxies can achieve that? But, again, only guessing.

[Chippy (Nick)]

Oh, I'm sure these encounters are "big" enough to do that.
"Streamers..." as in "the Magellanic Stream...???"

Obviously the outcome is dependent on a number of factors relating to the interaction (not JUST how "big"). Relative angles, distance, motion, mass, etc. Also depends to some extent on how you define "galaxy" and "intergalactic space". I expect the Magellanic Stream may lie somewhere in-between (for example).