 Greetings and welcome to the Introduction to Astronomy. In this video, we are going to talk about a couple of the objects in the outer part of the Solar System, and that includes the Kuiper Belt, which is a large set of objects outside and beyond the planet Neptune. So we'll look at the Kuiper Belt here, and we will look at the object that has been recently studied, and that is known as Arakoth. And that was recently studied by the New Horizons spacecraft. So we'll take a little bit of a look at that as well. So let's go ahead and get started here, and take a look at the next page. And what we find is that what we mean by the Kuiper Belt, what do we mean when we discuss the Kuiper Belt? Well, the Kuiper Belt includes the trans-Neptunian objects, or sometimes called TNOs. So these are objects that orbit out beyond Neptune. And we can see those in the image here. So we can see our Sun towards the center. And we see the outer planets, Jupiter, Saturn, Uranus, and Neptune. And then out beyond those we see all of these green dots represent the Kuiper Belt out here. So out here and around all these different areas show different objects that have now been detected in the Kuiper Belt. Now we've known of objects in the Kuiper Belt since 1930 when Pluto was discovered. Of course we did not know that it had anything to do with the Kuiper Belt at that time, but it was the first of these objects found. Here we found Chiron in 1977, which isn't quite into the Kuiper Belt. It actually orbits between Saturn and Uranus. And the first actual true Kuiper Belt object was discovered in 1992, and that was Folas. And when that was discovered, that was the first of many thousands of TNOs that are actually now known. So what are some of these objects? Well, let's take a look at some of the largest TNOs that we know, or Kuiper Belt objects. And among those are the dwarf planets. So the dwarf planets, some of the largest of these objects, and in fact there are four of those, are the largest TNOs known. And we see them here, Eris, Pluto, Makemake, and Hamea. As four of the largest of those, but there are also several others that are not quite as large that are visible as well. So there are some relatively large objects, although if you remember for comparison, Pluto is much smaller than our own moon. So even all of these objects together do not make up one Earth's moon. Now the only one of these that has yet been explored is Pluto. Pluto is the only one that has actually been explored by spacecraft at this point. Now these others, these are the ones, these top four are classified as dwarf planets. The ones on the bottom have not yet been classified, but are likely to meet that criteria and could be classified as dwarf planets in the future. So we're finding more large objects out there than we find within, for example, the asteroid belt closer in to the solar system. But at this point Pluto is the only object we have yet explored of these. So we can take a quick look at Pluto, and we've talked about Pluto before, and we see that Pluto is the only one that we've explored, and we can see that here. This is an image from New Horizons, where we see some of the different areas, some of the darker regions over on this side that have more craters on them, and then the very smooth, flat planes that have been flooded by icy materials wiping out any craters. So let's go ahead and look at what went on and how we got to look at some of these other objects out in the Kuiper Belt, or at least one of those, and exploration of the Kuiper Belt was done by the New Horizons spacecraft. Now this was launched in 2006 and began a nine year journey to Pluto arriving in 2015. Now that was the launch, and we can see the launch here, the rocket just taking off, launching New Horizons, and because of the great distance of Pluto it took a very long time for it to get there. Now if we wanted to look at how it did this, we can see here's a little trajectory of this showing how it moved, and we can see it leaving from Earth here, actually passing by Jupiter, and getting a little bit of a boost from Jupiter and speeding up, and then it passed Pluto out towards this area here, when it passed there Pluto was at that location, and then finally its mission was extended, and in order to extend it we had to find an object that would be at the right location. So we couldn't just take New Horizons and turn it around and head it over, way over to look at something on this side, or on this side, we had to look at something that was relatively close to the path. And we would use the gravity of Pluto to kind of give it a little nudge so that it went in the right direction, and the object that was found actually discovered in 2014, known as 2014 MU69, or sometimes now known as officially named as Arakath, and that is a much smaller object than Pluto, but it happened to be in about the right direction, and if you note it was actually discovered only the year before the fly by of Pluto, so it was not something that we knew of long and advanced, in fact it was discovered while New Horizons was on this journey, so it was still not known about when we launched New Horizons, but we found out in time it was actually on a really good path, and minor direction changes were able to get us to fly by this object. Now what did we see, well let's take a look at some of this, and what we saw here when we did it, New Horizons did fly by Arakath in 2019 on January the 1st, and we have a little clip here to see that we can play, and as we watch we will zoom in slowly looking for Arakath, and you'll start to see as we look at it here that we'll get a little bit closer and closer as we zoom in, it's a very faint object, not something that was easy to see, and would have been very difficult to find, that's why it took so long, as we get closer we'll start to see it resolve, and we'll see that it has an interesting structure as two parts to it, a larger part there on the left, and a smaller part, sorry a larger part on the right, and a smaller part on the left, and then we'll see as we continue outward and head back behind a very thin crescent shape of Arakath, as it heads back out in to, as the New Horizons heads out further into space. Now this is an example, let's take an image, take a look at an image of it here, it's an example of what we call a contact binary, it has two lobes, and the larger lobe here, and a smaller lobe here, these are very small compared to things like the dwarf planets, or the larger objects that we've looked at in the solar system, the largest axis of the larger one is only, so the larger axis of this one is only about 21 kilometers across, and if you think about that, it's only a little over 12 miles across, so not a very large distance, and the smaller one is only about 15 kilometers, or maybe about 9 miles across, so they're very small. Now when we say they're a contact binary, they're actually two separate objects that are just barely joined together right here, and they probably formed early on and collided, but not a drastic collision as we talk about with, say, the Earth and the Moon's formation, but a very gentle collision and they just kind of stuck together, so not enough to actually merge them into one solid object, but two objects very close, tied together. Now this might have formed, and we can see in the next slide here, we'll take a look at this, and what we see is this is perhaps how these things formed billions of years ago, we see that we had a lot of objects merging together, and what formed was two relatively large objects, one here and one over here, and they were slowly orbiting around each other, and they got closer and closer together until they collided and merged, thereby joining into one single object, and that's what we see today. Now this probably happened nearly four and a half billion years ago when everything was forming in the solar system, and it has been like that ever since. We also have noted that they have a very flattened shape, so if we look at the drawing here, how flat this is, it's more flattened like a pancake than it is a circular object, and that's quite possible in very small objects that do not have enough gravitational force. Any large object is going to be pulled into a spherical shape by its gravitational force. Smaller objects do not do that, and that's why we see smaller asteroids, and now we know smaller Kuiper Belt objects do not show this, and this is now the second Kuiper Belt object that has been explored, Pluto having been the first by New Horizons in 2015, and then Aracoth in 2019, so they're the only two that we actually have close up detailed images of, and probably the only two we will have for quite a while, because it takes, if we were to send other craft out there, it takes a long time, remember it took New Horizons nearly a decade from launch to Pluto, and that was not counting all of the time and planning and preparation here on Earth before that. So let's finish up and conclude here as we do with our summary, and what we find is we talked about the Kuiper Belt, and that's a collection of many objects out beyond the orbit of Neptune. Some of the larger ones of these have been classified as dwarf planets, and we looked at New Horizons, which visited both Pluto and Aracoth. So that concludes this lecture on the Kuiper Belt and Aracoth. We'll be back again next time for another topic in astronomy. So until then, have a great day, everyone, and I will see you in class. So that concludes our lecture on life beyond Earth. We'll be back again next time for another topic in astronomy. So until then, have a great day, everyone, and I will see you in class.