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fabula cluster is a big sphere of stars

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that have collected together they're

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orbiting around a Common Center but it's

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very spherical very organized looks like

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a huge basketball contains hundreds of

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thousands of stars these clusters have

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formed early on in the formation of a

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galaxy when the cluster starts farming

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it's a very diffuse and over time things

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get concentrated more and more toward

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the center

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stars are actually moving all around and

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if they're sort of orbiting around the

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center it's not a static cluster even

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though a single picture makes everything

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one of the more famous ones is Messier

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13.

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Omega Centauri is a prototypical one in

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the southern hemisphere

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globular clusters are very old there

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seem to be some of the first stars

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formed in the Galaxy as the material

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that came together in the past one of

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the pockets of condensed material that

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occurred around the center of the Galaxy

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grew together into the selections of

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stars so they're mostly very old SARS 10

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or 12 billion years old although we do

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see a second generation of newer younger

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stars in globular clusters still you

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know relatively old billions of years

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ago but it's not like it had one burst

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of star formation and that was it we did

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have a chance to form a second wave

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later on

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was still in one is what's called an

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open cluster it's a very loose

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collection of stars over a broad area

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it's more sort of a cloud of stars as

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more stars gather in an open cluster

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like that and more material comes

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together it's going to naturally pull

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things in toward its Center something

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like Western over many millions of years

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could evolve into something that looks

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more like a globular and we do think

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that most globulars have one or more

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black holes at the center which is a

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source of immense gravity to help hold

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these clusters together Hubble saw in

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the globular cluster NGC 6397 the first

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clear evidence for multiple black holes

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at the center we had previously assumed

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that most globulars would have a single

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black hole at the center in this case we

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found a number of separate black holes

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they're moving around each other at high

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speeds around a Common Center

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if you have a number of black holes in

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tight orbits around each other at the

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center that works as well as a single