What is Clusters: Definition and 70 Discussions

Star clusters are large groups of stars. Two main types of star clusters can be distinguished: globular clusters are tight groups of hundreds to millions of old stars which are gravitationally bound, while open clusters are more loosely clustered groups of stars, generally containing fewer than a few hundred members, and are often very young. Open clusters become disrupted over time by the gravitational influence of giant molecular clouds as they move through the galaxy, but cluster members will continue to move in broadly the same direction through space even though they are no longer gravitationally bound; they are then known as a stellar association, sometimes also referred to as a moving group.
Star clusters visible to the naked eye include the Pleiades, Hyades, and 47 Tucanae.

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  1. D

    Stars born in clusters, found in single

    So far as I understand, most stars found in the galaxy are single or double stars. However, they are born in nebulae by the hundreds. What happens to spread them out such? I would think that gravity would keep them together in the way that they were formed, by the hundreds. Or am I...
  2. R

    Expansion around gravitational clusters

    Hello everyone! Ok so from what I've read in various textbooks & wiki is that the red-shift of observed galaxies is caused by the expansion of space through which the light travels (naively seen as galaxies moving away from us and causing a doppler shift). This got me thinking that if 'our...
  3. S

    Can galaxy clusters rotate like individual galaxies?

    At scales of galaxies there is obvious rotational motion but I am wondering if there is an example of a rotating galaxy cluster or super cluster? The rotation could be detected by redshifts the same way it's detected for galaxies. Possibly the rotation would lead to squashing the cluster...
  4. nicksauce

    Galaxy Clusters & Superclusters: Definition or Ad-Hoc?

    Is there a rigorous definition for what constitutes a galaxy cluster or a super cluster, or are they just identified in an ad-hoc manner?
  5. F

    Evidence for Dark Matter Beyond Rotation and Clusters

    Besides keeping the whole of galaxies rotating at the same rate, and holding galactic clusters together, what are the other forms of evidence for dark matter?
  6. wolram

    Mysterious Motion of Galaxy Clusters Detected

    http://www.sciencedaily.com/releases/2008/09/080923104410.htm ScienceDaily (Sep. 24, 2008) — Using data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), scientists have identified an unexpected motion in distant galaxy clusters. The cause, they suggest, is the gravitational attraction...
  7. marcus

    Detecting Bulk Motion of 700 Clusters with KSZ Effect: Results & Implications

    some astrophysicists may have detected a slight average drift in a population of 700 clusters. I believe the clusters surveyed are relatively close to us, within distances on the order of a billion LY. (We see matter out to about 45 billion LY, so one billion is not anywhere near the horizon of...
  8. B

    Simulating globular clusters over blackholes with Fortran

    I suspect that the runtime simulation for a star systems containing thousands of stars , many of those stars whose mass is way beyond the solar mass to be very very long. Is it possible and cost-friendly(i.e, not expensive) to simulate a globular star system cluster over a supermassive black...
  9. R

    Estimating relative distances for star clusters

    If star clusters were all about the same physics size, how could one estimate their relative distances?
  10. R

    Clusters of Matter and Antimatter

    Does anyone have opinion on this paper by Dr. Mishustin on theoretical possibility of coexistence of matter and antimatter? : http://www.fias.uni-frankfurt.de/symposium/papers/mishustin.pdf Is such research being conducted elsewhere ?
  11. DaveC426913

    Characteristics of globular clusters

    Quick question(s): If a cluster is not "open", it's what? M62 is a what cluster? (No, not peanuty nougat). What would be the average distance between stars in a cluster like this? What would be the average orbital period? And ultimately, what would the motion patterns of stars in...
  12. S

    Why are Globular Clusters so Metal poor?

    I do not understand why Globular clusters, with ages around 10 Giga years, are so metal poor. Their stars are surely undergoing nucleosynthesis, right? Are all the stars in such cluster only of such low mass that they never explode as supernova and scatter their elements? TIA Sterling
  13. F

    How did globular clusters get their properties?

    As I understand it, the stars in a globular cluster have orbits with a whole range of eccentricities and directions of motion, giving the cluster an overall spherical shape, with a greater density of stars toward the center. How did the overall cloud out of which the globular cluster arose...
  14. E

    Should globular clusters exist?

    they are the oldest things in the galactic halo, having formed near the birth of the milky way. So with all the 10 odd billions of years of existence, i think they all should have gone supernova and destroyed the shape of the cluster. So how do they stay gloubular in their shape?
  15. M

    Nano particles and nano clusters

    what are the differences between nano particles and nano clusters?
  16. R

    Calculate the uncertainty of the distance to the clusters?

    Hi, Im sorry to make my first post a question but I am going mad trying to sort my problem. I've looked in all kinds of places for my answer but it never seem so to be there. Im in my 3rd year of an OU Physics degree, and currently writing up a report on some observations I made of star...
  17. M

    Titanic merger of galaxy clusters revealed

    This is amazing, I haven't heard of any merger of two galaxy clusters until now. http://www.newscientist.com/news/news.jsp?id=ns99996443 "One of the hottest, most energetic mergers of two colossal galaxy clusters has been imaged in exquisite detail by an X-ray observatory in space...
  18. B

    Gravitational field of globular clusters ?

    what does the gravitational field at the center of a globular cluster look like? it doesn't look as though there is any angular momentum - is there a 'center' of gravity inside? a black hole?
  19. wolram

    Exploring Super Clusters: Unanswered Questions

    does anyone have information about super clusters? will all galaxies eventualy end up in a super cluster? if not has there ever been an estimate as to how much of the mass of our universe will escape clustering? will these super clusters be so far appart that gravitational influence will...
  20. D

    Why do galaxy clusters form sheets?

    Greetings ! I just read Saint's post in the "moving galaxy" thread and though I knew the answer to that, I do not believe I have so far read somewhere an explanation for the existence of the galactic cluster sheets. So, is there a known and recognized reason ? (My guesses : 1. The...
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