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Globular clusters are the main focus of this video, a type of deep sky object that I have mentioned in previous videos, but they haven’t had their own focused video just yet. These ball of stars can be light years across, but I am excited for a much smaller number, 100. I have just surpassed the 100 subscriber milestone on YouTube, and so I have a special video to announce! This day next week I will be launching a video dealing with any questions you would like to ask, a 100 subscriber Q&A Special. You can ask the questions right here as a comment or on any of my social medias.

Without further ado, or at least until the next digression, we might as well start with the biggest globular cluster. To see it, we’ll have to take a trip to the Southern Hemisphere. The Omega Centauri globular cluster is the one, a ball of stars just around the outside of our galaxy. It’s so big and bright that it’s even visible to the naked eye, although it looks more like a star without a telescope to help. This is one of the times when the naming scheme for objects in space proves useful. It’s Omega Centauri, so it must be in the constellation of a Centaurus the Centaur, which is definitely a Southern Hemisphere constellation.

While we are in the Southern Hemisphere, we also get to see two other large groups of stars orbiting our galaxy, The Large Magellanic Cloud and the Small Magellanic Cloud. These are Dwarf Galaxies, much bigger and less globular than the globular clusters we’ll be concentrating on. However, some globular cluster, especially the giant Omega Centauri, may have started out this way. Bigger galaxies often swallow up smaller galaxies, and our Milky Way has certainly done that in the past. In this case, it may have pulled most of the stars away, leaving behind the core of the dwarf galaxy, what we see as Omega Centauri.

I take the opportunity in the video to show how clear the Magellanic clouds are when viewed from a dark sky in the southern hemisphere. If you are down South, in an area with little or no light pollution, you can see the Milky Way and its two dwarf companions with just your eyes. The Omega Centauri Cluster looks like a bright star, just on the other side of the path of the Milky Way through the sky. Unfortunately for us up North, these are pretty much Southern Hemisphere only objects, similar to our Plough or Big Dipper.

Which leads me to why they are named after an explorer from the Northern Hemisphere. You may notice that you can now comment on my YouTube videos directly, as they are no longer part of YouTube Kids. This isn’t so that I can start swearing or anything like that, but it does mean I can be a little less cautious when it comes to discussing things like Ancient Greek myths and legends. A little self-censorship is certainly necessary when trying to explain almost any story of Zeus to a younger audience, but I will be less cagey and indirect going forward. This alos means I can discuss things that may be considered contriversial, like. Ferdinand Magellan.

Ferdinand Magellan was a Portuguese explorer and he led the expedition that first circumnavigated the globe. He is who the Large Magellanic Cloud and the Small Magellanic Cloud are named after. The expedition did travel all around the world for the first time ever. It left Spain, went to across the Atlantic Ocean and around bottom of South America. It then completely crossed the Pacific Ocean although it took months, a lot longer than was expected. The explorers and their ships went through the Philippines, out the other side, across the Indian Ocean, around the bottom of Africa and all the way back to the Iberian Peninsula. There is no denying this achievement, the people on those ships, or just ship by the end, they were the first people to completely circumnavigate the globe. Unfortunately, Ferdinand Magellan didn’t actually make it the whole way, he died in a battle in the Philippines, but he was the original leader, it was his expedition, even if it finished with a new captian.

Even more unfortunately, as was the case for a lot of things in the 17th century, the Age of Exploration and Colonisation, Ferdinand Magellan was involved with various things that wouldn’t be allowed today. The most prominent issue, besides the colonialism, would be slavery and slave-ownership, even having a slave translator on the voyage and other enslaved persons. I find it personally unfair that Ferdinand had a private store of preserved fruits which contained vitamin C, which helped him survive the 3-month journey across Pacific Ocean, which not a lot of his crew survived. In the end only 18 or 19 members of the 270 members of the starting crew made it all the way back to Europe.

For these reasons, some people are pushing to rename the Large and Small Magellanic Clouds, and importantly there are many astronomers making this push, the very people that a change in name could inconvenience. It hasn’t been officially done yet so I’m going to call them the name they are still currently officially called, but it is an issue. Furthermore, it is a part of a much larger issue, When it comes to astronomy a lot of things were named back when astronomy was really taking off, around the time of the invention of the telescope, which was a very long time ago, the 1700s. At that time decisions were made and names were given that people wouldn’t necessarily agree with today. Of course, Ferdinand Magellan was a big important explorer and Portugal deserves things named after it or related to it. There is a planetary system, a star and planet, named Lusitania and Viriato, those are things that are up there, visible from Portugal. The Large and Small Magellanic Cloud are not, they’re on the other side of the planet, you can’t see them in the Northern Hemisphere. Personally, I believe that naming them after something related to the Southern Hemisphere would be appropriate, the Southern Hemisphere is where these things are actually visible and they deserve things named in their languages as well.

Moving back to globular clusters, they are ball of stars, and although some of them can be very dense in the middle, like Omega Centauri. While it is practically a solid ball of light in the center, you can see that it gets more diffuse around the outside and different globular clusters will get more or less diffuse than others. We can luckily also see many of them from the northern hemisphere, so we will move onto some of the ones that we can see from Ireland and other more Northern locations. A lot of them are going to be in the Messier Catalogue, a name that I’ve mentioned several times. I am going to make a video about the Messier Catalogue and all of the things that we see in the sky that start with M, even the Pleiades have an entry, they’re M45. Globular clusters bright things with a bit of fuzziness around the outside, which makes them easy to mistake for the comets that Charles Messier was really searching for.

One famous cluster visible here in the North is the Great Cluster in Hercules. Looking at it through a telescope you’ll see that it’s not quite as solid in the middle as the Omega Centauri cluster, it’s more diffuse. Most globular clusters have a morphological description, this one is “Intermediate concentrations of stars”, but others can be diffuse or concentrated, there is considerable variety. Globular clusters never look as spread out and loose as open star clusters like the Pleiades and the Hyades, of course the hint is in the name, while they are open clusters, globular clusters almost always look like a round and rather dense group of stars, without the open space visible between its members.

As I mentioned, we find these balls of stars around other galaxies, from spiral galaxies like our Milky way and the Andromeda galaxy to big elliptical galaxies like M87. Many globular clusters are very early entries in the Messier Catalogue, for example M2, M3 and M4, are all globular clusters. Many of them are really beautiful looking, almost like the inside of a geode, full of sparkles, but you really do need a telescope to enjoy them. Even the ones that are visible to the naked eye like the Omega Centauri cluster, if your telescope isn’t good enough, then it won’t resolve them as multiple little stars. Instead, it would look like a star, maybe a little bit of out of focus, it would just look like one bright dot. Only with magnification will you see the diffuse collection of stars which is what it really is.

There’s loads of globular clusters, for example the Andromeda galaxy is thought to have about 500 globular clusters, and bigger galaxies like M87 can have thousands of globular clusters around them. These tend to be arranged in a certain way, we see more globular clusters towards the center of a galaxy we do towards its edge. By looking at the distribution of globular clusters around our galaxy, an astronomer named Harlow Shapely was able to roughly figure out where we were in our galaxy, about three-quarters of the way out from the central bulge and a little bit in from the edge. It wasn’t exactly accurate because of the data that Harlow Shapely was working with, but it was pretty close.

The stars in globular clusters tend to be old. I mentioned that the Omega Centauri cluster may be a cluster that originated as a Dwarf Galaxy orbiting the Milky Way, that was then sucked in by our galaxy, or lost a lot of its stars to our galaxy, but some globular clusters may have formed from the galaxy itself. We know that an open cluster like the Pleiades formed out of dense regions of hydrogen gas, there’s a chance that globular clusters began as dense regions of hydrogen as well, that then formed a lot of stars which coalesced together into the huge balls we see today. However, it does look like a globular clusters contain stars of different ages and that’s a sign that they probably didn’t come from the same cloud of gas. This means that the globular clusters may pick up stars from the galaxy proper. I often compare this to fibers of wool making their way out of a woolen jumper. Short fibers start to poke out of the weave and can slowly wrap together, forming little balls or pilling. The little balls that old jumpers get on them, the pilling on your jumper as it gets older, it might be similar to the formation of a globular cluster around a galaxy.

At this time of the year in Ireland, morning time is when a lot of globular clusters come up because at this time of the year as we approach morning time, that’s when we’re starting to see the center of our galaxy, where globular clusters tend to cluster themselves. If we were to look out towards the edge of the galaxy, we’d see far fewer.

I hope you enjoyed that look at globular clusters and I want to thank all of you once again helping me attain 100 subscribers on YouTube. If you’re not one of my subscribers, you could be, if you’d like to subscribe to my YouTube channel you can be part of the next milestone. There will be a Q&A video next week, so you can post your questions here, on the YouTube video itself or send them to me on Instagram, under Caoimhín’s Content as well. Again I hope that you enjoyed this content and I hope that you’ll stick around for the next subscriber milestone in a few thousand more subscribers.