 Greetings and welcome to the Introduction to Astronomy. One of the things that I like to do in each of my introductory astronomy classes is to begin the class with the astronomy picture of the day. From the NASA website that is apod.nasa.gov slash apod. And today's picture, for October 16th of 2023, well, it is titled Eclipse Rings. So, what do we see here? Well, here we see a ring eclipse, also known as an annular eclipse. And is there a proposal going on in the foreground? And that's something, of course, we don't know for sure. But it has to be a very well-planned image to get an image like this. And as is noted here, the people had to travel a distance to be able to view the ring of fire eclipse that occurred on Saturday. Now, this is a type of eclipse that occurs when the moon is at apogee. This is the greatest distance in its elliptical orbit from Earth. Now, when something is more distant, it appears smaller in the sky. And it is a coincidence here on Earth that our sun and our moon appear almost exactly the same size in the sky, giving us things like eclipses, where the moon will completely block out the sun, but just barely do that. If the moon appeared much larger than the sun, then eclipses would be quite common with the moon always blocking out the sun, and it wouldn't be such a big deal. And you could also perhaps imagine a situation where the moon was much, much smaller than the sun, and while it would pass in front of the sun, it wouldn't be able to completely block out its light. So, what makes eclipses so unusual here on Earth is that the two objects are almost the same apparent size as seen from Earth. The moon much smaller, but many times closer. The sun much larger, but many times farther away. So, sometimes when the sun is at a closer position and the moon at a more distant position, the moon will line up with the sun, but not quite be able to block out its light completely. And there we see the ring of solar surface around the edge of the moon that was passing in front of it. Now, an annular eclipse is not super rare. They do occur relatively often, and in fact we get solar eclipses of some kind every year here on Earth. What makes them rare is that you have to be in the right location to be able to see it. And in fact, in this case, you had to be in parts of the western United States and then down through some of central and southern South America. But if you weren't in the right place within those regions, you still would not have been able to see this as an annular eclipse. You would have seen a partial solar eclipse. Still an amazing sight, but not quite the same as if you happen to be on that direct path of totality. And that's when you get to see an eclipse like this, when it occurs as an annular eclipse, or as a total solar eclipse, as we will have coming up next year on April the 8th. So that was our picture of the day for October 16th of 2023. It was titled Eclipse Rings. We'll be back again tomorrow for the next picture, previewed to be Dust Rings. So we'll see what that is about tomorrow. And until then, have a great day, everyone, and I will see you in class.