 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 September 25th of 2023, well it is titled ARP 142, the Hummingbird Galaxy. So what do we see here? Well this is the galaxy known by its catalogue designation of ARP 142, which is a catalogue of peculiar galaxies, or galaxies that don't look like ordinary spiral and elliptical galaxies. And certainly just a quick glance at this one shows it has some very strange features associated with it, including the fact that it may resemble a hummingbird, so you may be able to see the hummingbird's nose out there in the blue stretching out toward the left hand side of the image and the red eye of the hummingbird actually being the central portion of this galaxy. Now what causes a galaxy to be distorted like this? Well generally when we see galaxies that are unusually shaped we find that they are interacting galaxies, that there is another galaxy there that is causing this one to change its structure and shape. And that is what we are seeing here is the larger elliptical galaxy down toward the bottom has likely had a close encounter with this galaxy, with a spiral galaxy and has caused it to become distorted. Not only does it become distorted, but it also undergoes bursts of star formation giving us those high concentrations of blue stars that we see in the hummingbird's nose and around and up the top of its head and then down below into the body. All of those large blue clusters of stars that star formation would be enhanced by the fact that the galaxies are interacting and gas clouds are colliding together at a higher rate than normal giving us excess star formation. Now what will continue to happen here in time? Well the interactions will go on, the stars will continue to go through their lives and eventually fade out, new stars will begin to form again and we will see that the two galaxies will change. So what we see as a hummingbird galaxy today will not remain a hummingbird galaxy, it will slowly change and eventually no longer be have this shape. And in fact in the long run these galaxies will likely merge together into a much larger galaxy and we can expect that in another billion years or so that there would be just one galaxy here, the hummingbird having been consumed by the large elliptical galaxy that is nearby. So that's what happens to galaxies over time. They do slowly merge together and eventually become larger galaxies. So earlier on the history of the universe galaxies were much smaller. Now we see galaxies get much, much bigger over time and have continually grown from those small galaxies to the larger galaxies that we're used to seeing today. So that was our picture of the day for September 25th of 2023. It was titled ARP 142, the hummingbird galaxy. We'll be back again tomorrow for the next picture, previewed to be Big Blue Horse. So we'll see what that is about tomorrow. And until then, have a great day everyone and I will see you in class.