The Sun, in an Open Cluster

I read somewhere that the sun is part of an open cluster. If thats true,
wouldn;t it have to be awefully OLD for an open cluster?

What other stars are in the cluster? How many? How large is it? Any
nebula still left?

thanks

jjb

Jeremiah J. Burton wrote:
I read somewhere that the sun is part of an open cluster. If thats true,
wouldn;t it have to be awefully OLD for an open cluster?

What other stars are in the cluster? How many? How large is it? Any
nebula still left?

More precisely, the Sun was almost certainly formed as part of such a
cluster (based on virtually all young stars we see today coming in clusters
and associations). Open clusters lose their identities over time, for
at least two reasons. First, the more of the remaining gas is blown
away by the most massive cluster members (including their supernovae), the
less mass is left to hold the whole cluster together gravitationally.
On top of that, random encounters with stars and massive interstellar
clouds will strip stars away over time. These are reasons that there
are very few open clusters known to nearly as old as the Sun (M67 and
NGC 188?), and the number increases rapidly for smaller ages. By now,
Sol has lost track of the siblings, although there are a few nearby stars
with similar enough space motions that they might share a common
origin.

Bill Keel

Fellow Iowan Sam Wormley was saying
Several of the stars in the "big dipper"
have similar motions about the galaxy
as our sun.

Seems like I can remember reading long ago that Sirius seemed to be
moving along with this group too.
Marty

Marty wrote:

Fellow Iowan Sam Wormley was saying
Several of the stars in the "big dipper"
have similar motions about the galaxy
as our sun.

Seems like I can remember reading long ago that Sirius seemed to be
moving along with this group too.
Marty


I believe I've read that too. There is some doubt that
any of the stars mentioned in the this thread are the remnants of
the original cluster... mostly because the spectral types imply
big age differences.

"Jeremiah J. Burton" wrote in message
s.com...
I read somewhere that the sun is part of an open cluster. If thats true,
wouldn;t it have to be awefully OLD for an open cluster?

What other stars are in the cluster? How many? How large is it? Any
nebula still left?


I am amazed no one has mentioned Alpha C - A B and C for starters. At 4.36-
4.5 LYs away, they
sure do qualify. Alpha C A is some 7 Billion years old that again
qualifies. The sun is 5-6 Byrs.

http://www.alphacentauri.org/centauri.html

On Fri, 21 May 2004 01:42:24 GMT, "Thomas" wrote:

I am amazed no one has mentioned Alpha C - A B and C for starters. At 4.36-
4.5 LYs away, they
sure do qualify. Alpha C A is some 7 Billion years old that again
qualifies. The sun is 5-6 Byrs.

Based only on the system's nearness? It has a very high proper motion which
might argue against formation in the same cluster as the Sun (hint: plot the
proper motion backwards 5 billion years; is the system still close?) Also, if
the stars are a billion years or more older than the Sun, that argues against a
common origin, since star forming regions typically have lifetimes measured in
millions of years, not billions.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
Based only on the system's nearness? It has a very high proper motion
which might argue against formation in the same cluster as the Sun
(hint: plot the proper motion backwards 5 billion years; is the system
still close?)

Anyone have a list of nearby stars with U/V/W velocities?

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

On Fri, 21 May 2004 03:19:39 +0000 (UTC), (Brian Tung) wrote:

Anyone have a list of nearby stars with U/V/W velocities?

That's an interesting question. I don't think I've ever seen one. But there are
catalogs with very accurate proper motion and distance data (such as Hipparchos)
and also catalogs giving radial velocity from spectroscopic measurements, so it
would be pretty easy to construct such a list if one doesn't already exist.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Brian Tung wrote:

Anyone have a list of nearby stars with U/V/W velocities?

You may already know this, but the Yale Bright Star Catalog lists both
proper motion and radial velocity, along with position (of course) and
parallax. It should be straightforward to get a cartesian vector from
that.

The initial position in spherical coordinates is

P0 = (ra, dec, s)

where s, the distance in parsecs, is 1 / parallax. The position after
time t is

P1 = (ra + pra, dec + pdec, s + v)

where (pra, pdec) is the displacement due to proper motion and v is the
displacement due to radial velocity. Convert P0 and P1 to rectangular
coordinates and subtract to get the velocity vector (the displacement in
rectangular coordinates over time t).

- Ernie http://mywebpages.comcast.net/erniew

Ernie Wright wrote:
You may already know this, but the Yale Bright Star Catalog lists both
proper motion and radial velocity, along with position (of course) and
parallax. It should be straightforward to get a cartesian vector from
that.

Yes, but I was hoping not to have to do all that pesky work.

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