2026 July 22 - The Corona Australis Molecular Cloud and the Chandelier Cluster

[00:00:02]Greetings and welcome to the Astronomy Picture of the Day podcast.

[00:00:07]Today's picture is titled the Corona Australis Molecular Cloud and the Chandelier Cluster.

[00:00:15]So, what do we see here?

[00:00:18]Well, here we see a very complex star-forming region in the area of the Southern Crown or Corona Australis.

[00:00:27]So, this is to the left we see the Corona Australis Cloud. Now, this is a lot of different regions. It's got reflection nebulae, emission nebulae that are present there. The emission nebulae will be primarily red.

[00:00:42]Reflection nebulae tend to be blue. They are the scattering of light around stars that have formed. Whereas the emission nebulae are glowing hydrogen gas.

[00:00:54]Now, we also see some dark nebulae, dark dusty areas there as well. And those are regions where stars are forming.

[00:01:03]Now, the labels on here label a number of the different objects and there's a lot of them there. Certain ones are known as HH or Herbig-Haro objects. And you'll see a whole bunch of them off there on the left-hand side as we take a look at that section. Those are objects associated with very young stars forming. In fact, they're not the stars themselves. They are actually jets of material that are crashing into the material around the stars. So, as this star forms, it ends up emitting a jet of material. Our sun may have done this when it was forming nearly 5 billion years ago.

[00:01:43]That jet spirals out at a relatively high speed and crashes into the dust and gas around it. That energy release will energize it and that glow is what we see as the Herbig-Haro object. So, we see a number of them labeled here, HH with a number going, it looks like, from about 96 to 101.

[00:02:06]So, there's several different ones in this same region, all associated with star formation. Now, some of the other objects we see here listed are stars, specifically. Some are dark nebulae, dark regions where we're not quite seeing things like those Herbig Haro objects, as we mentioned before. They're still hidden, those stars have not gotten to that stage of formation yet.

[00:02:33]Now, around, if we look up to the upper right-hand side here, we see what is known as the Chandelier Cluster. And that is also known by its catalog designation NGC 6723.

[00:02:48]Now, this is a cluster of stars, and a very unusual one. In that it has stars that have formed over various times. So, it has some younger stars, some slightly younger than the very ancient stars that make up a lot of that cluster. So, those very ancient stars are essentially as old as the universe itself. These are some of the objects that formed very early after the universe did. But this one, instead of undergoing just a single burst of star formation, had several different bursts for some reason, and we can see different populations of stars, including some that are slightly younger.

[00:03:28]So, again, that helps us try to better understand how things formed, how our galaxy formed those billions of years ago after the Big Bang. This is one of those remnants left behind, and one of the very earliest pieces of the galaxy to form, whereas the rest of this is a very young star-forming region. So, while we see these two together in the sky, they're actually not associated with each other in the slightest. The star-forming region, only a few hundred light-years away, the star cluster we're looking at is tens of thousands of light-years away, just happening to be roughly in the same direction in the sky.

[00:04:11]So, that was our picture of the day titled the Corona Australis Molecular Cloud and the Chandelier Cluster.

[00:04:20]We'll be back again tomorrow for the next picture, previewed to be a friendly neighborhood galaxy.

[00:04:27]So, we'll see what that is about tomorrow.

[00:04:30]And until then, have a great day, everyone, and I will see you in class.