Globular cluster (Messier 3 / NGC 5272)

Globular cluster (Messier 3 / NGC 5272)

Globular clusters are quite different than open clusters. Most open clusters form, then live hard and die fast and/or move away from one another. Most open clusters form from a giant cloud like the Orion Nebula, which will one day also be an open cluster.

Globular clusters are shaped like fuzzy globes and orbit the halo of our galaxy, which the total amount in the Milky Way being around 160. They are bound together forever (usually) and most in our galaxy are just about as old as the Milky Way itself.

How they form and what holds them together is up for debate. It could be one of these reasons, or all of them. Messier 3 has about 500,000 stars whereas many open clusters I’ve posted contain anywhere from 100 to 1000 stars. Big difference. One or more black holes have been confirmed to live at the center of many globular clusters. Hence, it could be a high mass star went supernova and collapsed into a black hole, and now holds it’s still “alive” brother and sister stars. Some globular clusters contain evidence that they were once dwarf/satellite galaxies that the Milky Way has consumed.

Most visible globular clusters, such as this one (M3), are very, very far away. They are the most distant objects we can see within our own galaxy. This one is 33,000 light years away. Most stars we can see are within a 1,000 light year bubble of visibility (relative to Earth).

The fact that, like M3, these clusters contains hundreds of thousands, and even millions of stars is what makes these objects visible. Through the naked eye, they will appear as fuzzy balls (similar to most open clusters) and usually contain redder stars.



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