Star spacing

What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I'm looking at an astrophoto of M7 and the background is absolutely pasted
with stars. It got me thinking about how close some of them might actually
be. The closest star to Sol is what, 4 light years? Are the stars in the
background of the M7 photo closer than 4 light years apart? Or is 4 light
years a typical value, it's just that there's a whole lot more of them off
in the direction of the core of the galaxy?

-Stephen

On Wed, 20 Apr 2005 16:08:31 -0400, Stephen Paul wrote:

What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).


I seem to remember reading somewhere that two globular clusters could
conceivably pass through each other with a resulting very, very small
number of their respective stars coming into contact with each other.




--
Martin R. Howell
"Photographs From the Universe of Amateur Astronomy"
http://members.isp.com/universeofama...nomy%40isp.com

Stephen Paul wrote:
What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I think that in our neighborhood, typical spacing is a few light-years.
In the galactic center, probably more like a light-year or fractions of
a light-year.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I'm looking at an astrophoto of M7 and the background is absolutely pasted
with stars. It got me thinking about how close some of them might actually
be. The closest star to Sol is what, 4 light years? Are the stars in the
background of the M7 photo closer than 4 light years apart? Or is 4 light
years a typical value, it's just that there's a whole lot more of them off
in the direction of the core of the galaxy?

-Stephen


I just had my 15 year old son do some calculations, and he says that the
average distance between stars in our galaxy is 7.3 light years. He got
this number using 200 billion stars evenly distributed in a cylinder 10,000
by 100,000 light years.

Dennis

Dennis Woos wrote:
I just had my 15 year old son do some calculations, and he says that the
average distance between stars in our galaxy is 7.3 light years. He got
this number using 200 billion stars evenly distributed in a cylinder 10,000
by 100,000 light years.

Ten thousand light-years is a bit high for even the thick disc. I think
the thick disc has a scale height of 3,000 light-years (that is, its
effect thickness is about 6,000 light-years), and the thin disc has a
scale height of 1,000 light-years. I haven't read any recent literature,
so I don't know if these figures have been updated.

I also suspect that the scale radius is less than 50,000 light-years, but
I don't know about that for sure, either.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

Stephen Paul wrote:
What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I'm looking at an astrophoto of M7 and the background is absolutely pasted
with stars. It got me thinking about how close some of them might actually
be. The closest star to Sol is what, 4 light years? Are the stars in the
background of the M7 photo closer than 4 light years apart? Or is 4 light
years a typical value, it's just that there's a whole lot more of them off
in the direction of the core of the galaxy?

-Stephen



If memory serves, Neale Howard in one of his books quotes a figure of 8
light years for the average distance between stars in this arm of the
galaxy. I'd Imagine at the galactic center there a bit closer together,
as they are in globular clusters.

-Chris

"Stephen Paul" wrote in
:

What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I'm looking at an astrophoto of M7 and the background is absolutely
pasted with stars. It got me thinking about how close some of them
might actually be. The closest star to Sol is what, 4 light years? Are
the stars in the background of the M7 photo closer than 4 light years
apart? Or is 4 light years a typical value, it's just that there's a
whole lot more of them off in the direction of the core of the galaxy?

-Stephen



I recall reading somewhere that the average separation of stars in the
central bulge of the the galaxy is indeed much less than we have in the
outer spiral arms. A figure of 0.5 light years springs to mind but this
is a vague memeory. The star fields behind M7, I guess are between us and
the central bulge, so maybe an intermediate figure applies. Hopefully
someone will have a more definitive answer.

Klazmon

Stephen Paul wrote:

What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

I'm looking at an astrophoto of M7 and the background is absolutely pasted
with stars. It got me thinking about how close some of them might actually
be. The closest star to Sol is what, 4 light years? Are the stars in the
background of the M7 photo closer than 4 light years apart? Or is 4 light
years a typical value, it's just that there's a whole lot more of them off
in the direction of the core of the galaxy?

-Stephen

http://www.aoc.nrao.edu/~smyers/cour...tro12/L21.html

"...There is a high density of stars in the central region, seen in the IR.
The average spacing in the center is about 1000 AU, compared with 1.5 pc
(300000 AU) near the Sun!..."

Stephen Paul wrote:
What is considered a close spacing between stars? (and I don't mean in
arcseconds from our perspective).

Including or excluding double stars? The closest doubles can be so close
together that when one of them enters the giant phase its outer stellar
envelope crosses the Roche limit and falls down onto its neighbour. We
observe them as cataclysmic variable stars - and a source of much
amateur professional collaboration they are too.

I'm looking at an astrophoto of M7 and the background is absolutely pasted
with stars. It got me thinking about how close some of them might actually
be. The closest star to Sol is what, 4 light years? Are the stars in the
background of the M7 photo closer than 4 light years apart? Or is 4 light
years a typical value, it's just that there's a whole lot more of them off
in the direction of the core of the galaxy?

Mainly the effect of looking through a long section of the galactic
spiral arm - ditto for the milky way. Stars are a bit closer together
near the very centre of our galaxy but are mostly obscured by gas and
dust in the visible.

Globular cluster cores provide the highest stellar densities per unit
volume. Not sure off hand how close together they are though.

Regards,
Martin Brown

"Klaatu" wrote in message
. ..

http://www.aoc.nrao.edu/~smyers/cour...tro12/L21.html

"...There is a high density of stars in the central region, seen in the
IR.
The average spacing in the center is about 1000 AU, compared with 1.5 pc
(300000 AU) near the Sun!..."

Excellent link. Thanks!

-Stephen