What is Globular cluster: Definition and 12 Discussions

A globular cluster is a spherical collection of stars. Globular clusters are very tightly bound by gravity, giving them their spherical shapes and high concentrations of stars toward their centers. Their name is derived from Latin globulus—a small sphere. Globular clusters are occasionally known simply as globulars.
Although one globular cluster, Omega Centauri, was observed and thought to be a star in antiquity, recognition of the clusters' true nature came with the advent of telescopes in the 17th century. In early telescopic observations, globular clusters appeared as fuzzy blobs, leading French astronomer Charles Messier to include many of them in his catalog of astronomical objects he mistook for comets. Using larger telescopes, 18th-century astronomers recognized that globular clusters are groups of many individual stars. Early in the 20th century, the distribution of globular clusters in the sky was some of the first evidence that the Sun is far from the center of the Milky Way.
Globular clusters are found in nearly all galaxies. In spiral galaxies like the Milky Way, they are mostly found in the outer, spheroidal part of the galaxy—the galactic halo. They are the largest and most massive type of star cluster, tending to be older, denser, and composed of fewer heavy elements than open clusters, which are generally found in the disks of spiral galaxies. The Milky Way has over 150 known globulars and possibly many more undiscovered.
The origin of globular clusters and their role in galactic evolution remain unclear. Some are among the oldest objects in their galaxies and even the universe, constraining estimates of the universe's age. Star clusters are often assumed to consist of stars that all formed at the same time from one star-forming nebula, but nearly all globular clusters contain stars that formed at different times, or that have differing compositions. Some clusters may have had multiple episodes of star formation, and some may be remnants of smaller galaxies captured by larger galaxies.

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  1. Barbequeman

    Virial Theorem for an expanding globular cluster

    I attached a file which shows my attempt to resolve this problem with the possible two pair interaction which gives us the kinetic energy of the cluster in an expanding system, at least I think so. But to be honest I´m more or less completely stuck with this question and I would be glad if...
  2. ISamson

    B Chemical study of an old, metal-rich globular cluster

    Regarding a recent article from phys.org , Chilean researchers have conducted a study of an old, metal-rich cluster, NGC 5927. Interesting results are the abundance of many metals, which include sodium, aluminium, iron, oxygen and some heavy metals such as yttrium and zirconium. Thank you.
  3. C

    Milky Way stole its farthest star cluster from another galaxy

    by Ken Croswell Call it the case of the purloined star cluster. Observations reveal that our galaxy stole a distant globular star cluster from one of its neighbours. Link: New Scientist
  4. Andy Resnick

    Is Stacking RAW Images the Key to High-Quality Astrophotography?

    Virgo has moved on, Hercules is now in position- from last night: This is a downsized crop. Technical deets: 800/5.6, 10s ISO 2000, 204 frames.
  5. J

    Globular cluster luminosity function

    So I was interested in how astronomers measure the distances to other stars, galaxies, etc and I found this pdf about the subject http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1992PASP..104..599J&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf It seems to be a good...
  6. liometopum

    Black holes in the globular cluster M22 with Dr. Tom Maccarone

    Dr. Tom Maccarone is a coauthor of the paper, “Two stellar-mass black holes in the globular cluster M22”, and is Associate Professor,Department of Physics, at Texas Tech University at Lubbock Texas. The work is discussed in a popular form at "Physicists Find Black Holes In Globular Star...
  7. liometopum

    Globular cluster ejected from M87

    In preparing a post for the globular cluster thread, I found reference to "High Velocity Globular Cluster One, or HVGC-1. This is the first globular cluster discovered to have been ejected by the interaction of two massive black holes. http://hvgc-1/ A Globular Cluster Toward M87 with a Radial...
  8. P

    Calibration cosmic distance scale on age globular clusters

    Hi, Could someone enlighten me in this matter? . how the calibration of cosmic distance scale affects the determination of the age of globular star clusters? thanks a lot :)
  9. vrmuth

    What is the center of a globular clusters made of?

    what's the center of a globular cluster , is it a star or can it be a black hole ? how are they formed and bound to gravitational pull of the milky way
  10. GiantSheeps

    Best way to see Andromeda galaxy

    I just recently got a dobsonian reflector telescope, (Orion SkyQuest XT8 PLUS Dobsonian Reflector Telescope) and I was wondering what the best way to see the andromeda galaxy would be using the telescope? Of these, which would be the best eye piece for that sort of thing?: Orion 2" 28mm...
  11. T

    Determining the mass of globular cluster?

    : Estimate the mass of a globular cluster with the radius of R=20pc and root mean square velocity of stars equal to Vrms=3km/s i can apply the formula like Vrms=(root over) 3RT/M ( where R=gas constant, T= absolute temperature, M=mass of the cluster) but here the variable of the "T" is...
  12. C

    Calculate distance between stars in a globular cluster?

    Would it be possible to calculate the approximate distance between stars in a globular cluster by doing something simple like this: Approximate distance to a cluster: 25,000 Ly Two stars in the cluster just barely resolved in my telescope (resolution about 1 arcsec) Therefore: 2pi...