Several questions about globular clusters.

I have been reading some bits about globular clusters, and became
interested and intrigued about them.

Therefore I decided that I would ask the great astronomers of the web
several questions about them.

Now globular clusters can contain from tens of thousands on up to
hundreds of thousands of stars, and can span distances of tens, up to
a hundred or two hundred light years across.

In some of the denser regions of a globular star cluster, you can have
an average stellar separation of as little as .3 light years. This is
pretty amazing, when you consider that the distance between proxima
Centauri, and alpha Centauri A and B, is about .1 light year.

I have read that distinct stellar binaries are still possible in
Globular star clusters. All of the stars in a globular star cluster
are bound to each other by the mutual force of gravitational
attraction, and many stars have elliptical orbits that will go down
into the interior of the cluster and then back out again.

Many stars in globular clusters have very old stars in them that may
have formed when the universe was very young, and do not have many
heavy elements associated with them. They revolve around the galaxy
in circular orbits sometimes outside the galactic plane. They are
often used to calculate the distance to other galaxies.

I have several questions about them.

Do the lack of heavy elements in some of the older globular star
cluster systems automatically preclude the existance of very many
terrestrial planets within them? Should solar systems with rocky
terrestrial planets only exist in the more younger globular star
clusters?

How stable, and how long, could solar systems exist in globular star
clusters? Are close flybys of one star to another very frequent in
globular star clusters?
Should solar systems be able to remain present long enough for life
toform and evolve in globular star clusters, or would the
gravitational dynamics of passing stars gradually have a high
probabilty of pulling them apart on the time frames of billions of
years?

How frequent are stellar collisions in globular star clusters? Are
they still nearly impossible or do they occasionally occur?

Would an interstellar civilization be able to more easily develop in a
globular star cluster because of the closer distance between stars?

Any comments, suggestions, or explanations would be appreciated.

"A" == Anonymous writes:

A I have been reading some bits about globular clusters, and became
A interested and intrigued about them.
[...]
A Many stars in globular clusters have very old stars in them that
A may have formed when the universe was very young, and do not have
A many heavy elements associated with them.

It is certainly the case that the globular clusters that orbit the
Milky Way contain only old stars, with ages only slightly less than
the age of the Universe. I believe that some other galaxies contain
what appear to be young globular clusters, that is, globular clusters
containing only young stars.


A I have several questions about them.

A Do the lack of heavy elements in some of the older globular star
A cluster systems automatically preclude the existance of very many
A terrestrial planets within them? Should solar systems with rocky
A terrestrial planets only exist in the more younger globular star
A clusters?

Good question.

The conventional wisdom is certainly that globular clusters should not
contain terrestrial planets for exactly the reason you mention, the
lack of metals. However, there is no way to subject this hypothesis
to any observational test at the current time.

[...]
A How frequent are stellar collisions in globular star clusters? Are
A they still nearly impossible or do they occasionally occur?

They are frequent enough. A recent Astronomical Picture of the Day
(APOD) had a picture of a globular cluster, in which several blue
stragglers could be seen. Blue stragglers are a kind of star that
appears too young to be in a globular cluster. The idea is that they
originate from collisions between two or more stars. The collision
would mix the two stars, and the resulting star could return to
burning hydrogen and appear younger than it actually was.

A Would an interstellar civilization be able to more easily develop
A in a globular star cluster because of the closer distance between
A stars?

Who knows. We don't know that civilizations can move between stars,
and we don't know if civilizations can develop within globular
clusters.

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