2026 March 16 - NGC 1566: The Spanish Dancer Galaxy

0:00Greetings and welcome to the Astronomy Picture of the Day podcast. Today's picture is titled NGC-1566, the Spanish dancer galaxy. So what do we see here? Well, here we see the spiral galaxy known as NGC-1566, also known by its more popular name, the Spanish dancer galaxy. Now this is an example of what is called a grand design spiral, meaning that it has very prominent spiral arms that swirl out from the center and are not significantly distorted by interactions with other galaxies. So currently this galaxy isn't interacting with others, that doesn't mean it never has. In fact we can say with certainty that yes, it has interacted with other galaxies in the past, and we know that because that's how galaxies grow from smaller galaxies into

1:00larger galaxies. And we find that the very early galaxies to form were much smaller than the galaxies we see today, so that all the galaxies we see today, including this one and our own Milky Way, grew through mergers and cannibalization of other galaxies. Now that doesn't mean that it's not having some interesting things going on with it. In fact it is classified as an active galaxy, and an active galaxy, in this case known as a seafird galaxy, which is a spiral galaxy, with an unusually bright core. So at this point, the core is producing more energy, the central black hole is being fed more materials being pushed into that, and as the material spirals into the black hole, it heats up to very high temperatures, emitting extra light, and that's likely what is happening here. We can also see all the telltale signs of star formation in this galaxy, including the

2:03bright red dots around the spiral arms, which are large star forming regions. These are regions of ionized hydrogen gas. A similar thing in our own galaxy would be the Orion Nebula, which is very prominent, and would be something like this on a much smaller scale, the Orion Nebula would hardly be visible at this range and distance of this galaxy to us. We only see it so prominently because it happens to be relatively close to us even within our galaxy. We can also see the bluish color of the spiral arms around there as well. Those are the clusters of stars that form from the gas and dust in the galaxy. The first stars to form, the brightest stars to form, the hottest stars to form are the blue ones. They dominate the light of the spiral arms, and that's because those stars are born, live their entire lives in the spiral arm, and then die before they have a chance to leave

3:03it. They don't live for a very long period of time. In fact, a star can take hundreds of millions of years to make one orbit around the center of its galaxy. For our own sun, it's about 250 million years that it takes to make one orbit. And that means these stars that only live a couple million years barely get a chance to move within their spiral arm before they have completed their lives. So here we get to see an example of a grand design spiral galaxy with great swirling spiraling arms coming out from the center of the Spanish dancer galaxy. So that was our picture of the day, titled NGC 1566, the Spanish dancer galaxy. We'll be back again tomorrow for the next picture. So until then, have a great day everyone, and I will see you in class.