Caoimhín's Content

I hope that some of you got to see the Blue Moon the evening before last. On the sunset of the 31st of May, we had our second Full Moon of the month, the Blue Moon. We are looking just a little bit ahead into June today and so the Moon is going to be just a little bit past full.

The sky that we’re seeing at the moment is the summer sky, we’re certainly in summer now. We have our bright star Arcturus pretty much dead in the south as darkness kicks in. This will be at almost 11:30 and darkness still won’t have fully kicked in. We still have that glow of sunset almost over in the northwest, and a little bit of that glow will stick with us all night long. We’ll move forward just a little bit so the sky gets as dark as it’s going to get. Close to midnight the Moon is just about to rise and bring a reasonable amount of light back into the sky, the Moon is just past full. However, as mentioned in a recent piece , the Moon is going to be pretty low in the sky all night long. You can take a look at some of my recent pieces to find out why. We want as dark a sky as we can get because we’re going to be looking at distant objects, deep sky objects outside of our galaxy. We’re going to be looking for another kind of galaxy, a kind of galaxy that our galaxy is not, we’re looking for active galaxies. Often when we talk about active galaxies, we talk about active galactic nuclei, the active black holes in the centre of these galaxies. When we talk about active galaxies, what we’re really talking about is their active black holes. When I say active black holes, I mean black holes that are actively taking something in. Many active galaxies are very distant from us.

We’ll get rid of the ground and the atmosphere so we don’t have to worry about looking at things that wouldn’t be visible from our location, such as Centaurus A or the Hamburger Galaxy. It’s called the Hamburger Galaxy because the dark dust at the edges looks kind of like a burger in the middle with the two buns formed by the core of the galaxy on either side. This is an active galaxy, so that means that there is material falling into black hole in the center of this galaxy. That material is generating jets coming from either end of the black hole. These jets are tough to see clearly in many images. This galaxy is almost 16 million light years away from us, so this is an incredibly distant galaxy from us. These galaxies that we see as very far away, millions of light years, that means we’re looking millions of years into the past, and even on the scale of a galaxy that many millions of years into the past makes quite a big difference.

Another active galaxy is The Eye of Sauron, quite an apt name for a galaxy that does look a little bit like an eye. This is a spiral galaxy that’s not quite a normal spiral, not quite a barred spiral, and it has a little bit of a ring structure around the actual center of the galaxy. With this galaxy in particular, because we’re looking down on the center of it, that means any material getting ejected from around its black hole is pointing roughly in our direction. This is only listed as an active galaxy but active galaxies are often broken down into quasars and blazars, not just active galaxies, based on where the jets are pointing.

The blazars in Stellarum don’t have common names, just different catalog numbers. For example the New General Catalog and the International Catalog are different catalogs that keep track of galaxies. There are so many galaxies out there, of course, not all of them have images that are loaded into Stellarium, and particularly these ones that don’t have common names. Galaxies with common names seem to be more likely to be included in the various Stellarium catalogs and lists. Quasars and blazars are both different types of active galaxy, they both have jets of material streaming away from the black holes in their centers. The difference is where exactly they’re pointed. Galaxies whose jets are pointed in our direction, pointed directly at us, those are blazars. The galaxies whose jets are almost pointed at us, not quite pointed at us, but pointed generally in our direction, those are quasars. In Stellarium it doesn’t look like we have quasar listed as an individual object, we only have bright quasars, and unfortunately, none of them look particularly bright, none of them are coming up as images in Stellarium.

The Bubble Galaxy is another galaxy that is millions of light years away, 53 million light years away from us. When the galaxies were younger, when the universe was younger millions of years ago, there was more instability in the centers of galaxies and galaxies were swallowing up more of their nearby dwarf galaxies. As that material falls in towards the center of a black hole, it gets accelerated. It ends up orbiting very fast as it gets close to the center of a black hole. This generates a lot of energy, it generates radiation including light. Some of the material that falls in towards a black hole doesn’t actually fall all the way into the center. Instead it gets accelerated out from the poles of the black hole. Those jets of accelerated material really are what tell us that the galaxy is active, and as mentioned the jets that come from the galaxies are often quite difficult to see. Back to the Centaurus Galaxy, it does have jets coming away from the poles of its black hole, but they’re not quite visible in this image used in Stellarium. The galactic jets are really what people want to study because they have material moving very fast, close to the speed of light, sometimes at the speed of light. Sometimes it at least seems like the material is moving faster than the speed of light in superluminary motion. When these jets are pointed straight at us, we can get a better idea of how the jets are fluctuating, getting brighter and getting fainter, and how the jets behave as one end of the jet slows down and new material catches up behind it.

It is difficult to see the jets of the galaxy and the galaxy itself, often the jets are a little bit fainter than the actual galaxy, so images that are trying to capture the galaxy itself, they often don’t capture the jets that are stretching away. We’re moving onto another Hamburger Galaxy, another active galaxy. It kind of has a “patty” in the middle and the bun around the sides. That patty is really lanes of dust and gas, dark lanes of dust and gas around the edge of the galaxy. This is similar to the darker parts of the Milky Way, when we look at the Milky Way, parts of it do look a little bit darker and those are those lanes of dust and gas. Looking at the Helix, or Pancake, Galaxy, it’s a little bit fuzzy so we can’t really see jets, but it looks like there might be an indication of jets, but because of the angle at which we’re seeing this galaxy, it’s very tough to tell. The jets that a galaxy produces are incredibly bright, full of energy, but they’re still not always as bright as the trillions of stars forming the galaxy itself.

The Markarian galaxies are best known from the VIrgo cluster, but some of the galaxies called Markarian’s are up by the Plough or the Big Dipper. Markarian’s Chain, of course, is closer to the constellations Leo and Virgo. Some of the galaxies in the Chain are no doubt active galaxies, but because of the way that Stellarium assigns pointers to these images of multiple galaxies, I’m not entirely sure which. The galaxy used to represent the Chain is just described as a galaxy rather than active galaxy, so I’m not entirely sure that the elliptical galaxy is the active one out of this chain. There’s a good chance that it is actually one of the other galaxies that is the active galaxy. Looking to the Meathook Galaxy, it seems to be pretty distorted due to gravitational interaction with a neighbor, giving it a strange S-shape. Regardless, it’s an active galaxy, on of the galaxies whose black hole is actively taking in material and generating jets coming out of it. By studying the material moving through those jets, people have an opportunity to learn about the black hole that created them and study material at really high energies, at really high velocities, conditions that would be, at the moment at least, impossible for us to recreate on Earth.

Those are some active galaxies, with common names. I hope that you enjoyed reading about them and hopefully you have a better idea of what quasars and blazars really are. Of course, they have very interesting names, but what they really are are the jets active galactic nuclei cause quasars and blazars, but quasars and blazars are really just kinds of active galactic nuclei viewed at the right angles. Hopefully you have a better idea of what makes the different kinds different now. If you enjoyed this piece, please do like it. If you like this kind of content then please subscribe to this website and my YouTube channel. Thank you very much for reading, and hopefully I’ll see you back here next time.