What are Globular Clusters? Relics of the Early Universe

One of the most beautiful and scientifically interesting objects in space are the globular clusters, containing hundreds of thousands of stars. What are they and where did they come from?

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Chloe Cain - Instagram: @chloegwen2001

I know it’s all aliens this and black holes that. Kugelblitzes, Sea Dragons and the dreaded vacuum decay. But sometimes, you just want to talk about something that might seem a little boring, but in fact, is one of the coolest objects in the night sky.

An enormous cluster of stars, many light years across and containing hundreds of thousands of stars. I’m talking about globular star clusters, of course, and they’re one of the best objects you can view in a telescope, and one of the most useful objects for scientists to study.

Now, before we get into the episode, I need to talk about pronunciation. In the past, I used to call them “globe-u-lar” clusters. But I got all kinds of heat from my astronomer friends, so I half retrained my brain to call them “glob-u-lar” clusters. But then I got dug into the proper pronunciation, and it turns out both methods are fine.

Which means that I’ll probably switch back and forth as we go, making you wince in my humiliation. That’s fine.

If you look out into the night sky with a telescope, there are few different kinds of star clusters. There are the open clusters, loose collections of stars nearby one another. Some examples of this might be the famous Pleiades, or Hyades star clusters. They’re what’s left over from a stellar nursery like the Great Nebula in Orion.

But a globular cluster is a much different object. Instead of a few dozen stars, globular clusters can contain hundreds of thousands of stars, bunched together into a region up to 100 light-years across.

On average within the Milky Way, stars are separated by about 5 light years, or about the distance from the Sun to Alpha Centauri. But within globular clusters, stars are only about a light year apart, even closer down in the core of the cluster. Just imagine what it must be like to stand on a planet orbiting one of these stars, and seeing a night sky alive with bright stars. It would be amazing.

Across the entire Milky Way, there are about 150 known globular clusters. There are probably a few dozen more hiding behind the disk of the galaxy from our vantage point. And as we look out into the Universe, we can see that all other galaxies have them too. Andromeda is much larger than the Milky Way and it has hundreds, while smaller dwarf galaxies like the Large and Small Magellanic clouds might only have just a few. Mighty elliptical galaxies could have tens of thousands.

The closest globular cluster is known as NGC 6397, located just 7,200 light years from Earth. It’s one of the smaller clusters with a mere 400,000 stars, measuring about 75 light-years across. But if you’ve got nice dark skies without light pollution, you can just barely see it with the unaided eye.

The largest cluster in the Milky Way is the Omega Cluster, only visible from more southern skies. This monster is 15.8 thousand light-years away and contains 10 million stars. It’s so big and filled with stars that some astronomers think it’s actually the core of a dwarf galaxy that was consumed a long time ago. You can also see the Omega Cluster with the unaided eye, even though it’s farther. It measures 150 light years across, but from our perspective, it appears like faint circle about as large as the full Moon.

Of course, as a Canadian, I’ve never actually seen it. So, enjoy that you lucky lucky Australians. That and all that other cool stuff you can see from the southern hemisphere, like the Large and Small Magellanic Clouds, and Alpha Centauri.

They’re pretty to look at, but globular clusters are very useful for science because you’ve got an enormous number of stars in a tight region. Mayhem can happen.

One exotic object found in some star clusters are known as blue stragglers. These are hot blue stars found within clusters, which stopped forming new stars billions of years ago. All of the large hot stars should have died as supernova, so blue stars shouldn’t be there.

Recently astronomers realized that these blue stars are actually the result of stellar collisions, where two stars came too close and collided. This added mass and mixed up hydrogen from the collision creates a much hotter star than anything else in the cluster.

[jerbilourimi]

"Stars are only about a light year apart", to those of you don't have clue how much a light year is, it is 5878668575518.969 miles

[wsmith]

In answer to your question: I saw at least a dozen globulars as a kid, when I converted my paper route money into a 6" f/8 Newtonian reflector. My fave was Lucky M13, in Hercules, perhaps the brightest (in apparent magnitude) of all the globulars and high up in northern latitude skies. M4 was cool, too, and easy to find, being practically in the same field as Antares, Heart of the Scorpion. I don't think, however, I ever saw NGC 6397, the closest globular to us, probably due to its excessively low declination (-53 degrees), putting it down in the smog from my +38 degrees latitude of the day. Thanks for bringing up these fond memories! Especially of M13, in my senile opinion the fairest of them all. Please keep up the good work, your videos are FANTASTIC!

[bonniebarton]

Thanks Fraser. Marvelous presentation. My dad belonged to San Jose Astronomical Association for many many years. He kept loaner telescopes for the club and loaned them out. He ground his own telescope lenses. He went to public viewing night every month for many years, educating countless members of the public about astronomy . He had a 10" reflector telescope. Very heavy to lift and to set up at star parties in Henry Coe state park and Grant Ranch, both south east of San Jose. I've looked through his telescopes many times. Magical!

[connielouisekendall]

One correction milky way is bigger than anything in local group including adromada. 120, 000 light years across twice previous size previously thought. Not smaller th adromada

[UpcycleElectronics]

Rain rain go away
Fraser's background isn't so green today

[airplanegirl]

Fraser, Nice presentation on Globular Clusters. Yes, for those interested, definitely determine where your local amateur astronomy organisation, or local observatory is, that organise "Star Parties". and then go.

We have one here in 29 Palms, California, at the "Sky's the Limit" Observatory every Saturday night that does not have a full Moon. We have several volunteers who set up telescopes to share views of the Planets, open and globular star clusters, Nebula, Galaxies, and occasionally the stray comet. Times are just after it becomes dark, and depending on who shows up, could last all night if someone decides to stay that long. Most events last three to four hours.

From 10-12 November 2017, we participate with the Joshua Tree National Park (JTNP) to put on the "Night Sky Festival". We had nearly 1000 people participate last year, and expect this year to be even bigger. Joshua Tree National Park is designated a "Dark Sky" site, so if you have a telescope, and are in the local area, come up and have some fun, any night, as our Campus is open to the public 365 days a year. We are on the border of JTNP, but are not affiliated with the Park.

[derivious]

my favorite thing to view from my scope is jupiter. the 4 main moons are like diamonds, always in a new position so im never bored. When showing friends saturn always gives a wow factor i remember resolving the image for the first time to this day. seeing the oval shape and the holes between the rings appear before my eyes did make me sweat with amazement. when mars was last at its closest that was amazing too. seeing dark brown patches and the ice caps made me humbled.

[MM-cccd]

Boring? You keep doing what you want to do. That was a great video. All new to me. Thanks

[luft]

As a young boy, I was told by my father that a Globular Cluster was a senior citizen community where old stars went to retire. Many years late, I still like to think of them that way.

[bryandraughn]

My dad bought a telescope for me when I was 7 years old because I was inseparable from our Time Life illustrated encyclopedia book, "Our Universe". This was in 1977, so I had to figure out everything by myself.
On my first attempt that very night, I caught 2 planets in the same field of view. Not sure which ones because I hadn't quite figured out how to focus using the various eyepieces that came with the previously owned, Jason Empire, 4" refractor. I got real good, real quick, and eventually spotted a fuzzy looking thing almost directly south in the fall sky. I almost lost my mind when it resolved into a ball of stars! I found 1 or 2 others that weren't as impressive but I didn't know what any of them were called. I had no reference material to identify things back then and the telescope gradually fell into disrepair. Recently, I bought a 6"(!!!) reflector and I've been building a case for it so I can take it up into the nearby mountains without knocking out the collimation. Lol! I have a nice selection of lenses for it and can't wait to check it out!
Love your channel, thanks for doing such a good thing for the curious minds around the world!
Peace.

[derivious]

I had a customer come into my work today. we was looking at mini arduino cameras to attach to a cubesat thats being sent to the ISS as part of a combined school project. Kind of made me sort of love my meager job for that moment. We then had a good conversation on how the definition of moon is clearly broken.

[f-s-r]

Omega Centaury in a dark sky is just incredible. I watched it in a star party, with my 150/750 telescope and a 18mm 60 degree eyepiece. The object was at the zenit, also. The cluster occupies almost the entire field of view, the stars look perfectly defined, colorful, and very bright. A spectacular object.

[MusiCaninesTheMusicalDogs]

Australians are not the only lucky southerns, you know?! Greetings from Brazil! ;)

[akashdakoor]

Extremely useful video and follow up playlist. Thank you!

[wanderingquestions]

Great topic! Well done. I agree GCs are often my favorite targets.

[DylanODonnell]

Hey thanks Fraser, I remember asking you about globs on your personal livestream not so long ago. Thanks for diving into this topic! The collision stuff makes a lot of sense to explain the blue stars. I'm not sold on black holes being found in them, I think their morphology suggests they lack a black hole, otherwise they might have a stronger rotational and elliptical plane like galaxies. Perhaps they are proto-galaxies of their own, lacking a black hole but fuelled by collisions near the center so they form this globular symmetry. As more stars are sucked and collided, they slowly grow their internal density and gravitational pull. In theory if they hoover up enough stars to continue the collision process they could become dense enough to create a central black hole and become a small galaxy. I don't know anything about anything but that's my guess. What do you think?

[VRShow]

Seeing your first globular star cluster with a telescope for the first time and really I mean ALL scopes...SCT, Newtonian, Dobsonian or refractor you WILL be impressed. Due to how the light gathering works its usually CCD and long exposures that coax out the colours and details of amazing deep space objects but after planets for your eyes only, my recommendation would be star clusters...you will be awed by their majesty!

[kurtreber]

I have soo much Fraser Cain to catch up on. I hope the Friday sessions start up soon.

[EdWalzak]

I was in Malawi this week, went out to take pictures of the stars but it was too hazy. Malawi runs on firewood and charcoal, and millions of cooking fires make stargazing difficult.

[earthexpanded]

If we reconsider the whole solar system atom model and suppose a galaxy is an atom too, then this globular clusters make a lotttt of sense as following similar patterns to Earth's history. If we imagine that around these stars are smaller objects like planets, and around those smaller still, and smaller still, filling the space between the stars, then these globular clusters coalesce into a single object in space.

I truly believe this is like taking an x-ray image of a planet. Seeing all its chakra energy points that are of the highest energies, and then seeing through the space between them to give a sort of skeletal view of a planet. And of a star and every other particle in the universe because all systems function identically, just seen from different angles.

Earth also formed in waves. It has undergone multiple major resurfacings of the crust as the Earth erupted. The first time, it was physically much more like Mercury and it literally underwent a planetary supernova to become as Venus is today. And then when Venus of today, which was like Mercury before, also underwent its own planetary supernova, it caused our Earth--like Venus is now--to be like Earth of today. Except, it was a single landmass. The system was knocked out of balance by the supernova of Venus and it began to rotate and this caused its electromagnetic field to be sort of "turned on", as a physical flow of particles through the planet was caused to flow, which due to high concentration at the center of the planet then produces more macroscopic mass, then trapped within the planet that it was initially able to enter as more subtle particles, until the crust ruptured and the Earth physically expanded. This is where the oceans were created.

Thus, Earth contains written in its crust and layers a history of having ancient shields, surrounding continental shelf, and ocean floors. These each sequentially formed in waves. As, too, the waves of star formation occur in globular clusters.

And we are able to, with our x-ray eyes, penetrate the interior of these globular clusters and observe similar processes occurring across the octaves of the infinite universe.

My two cents. Thanks for the video, I appreciate the information! Please pardon my plausible insanity.