If you want to explore more about exoplanets their properties, what we know about them, how many there are, where they are, anything else that we know that you might imagine. The go-to place is exoplanets.org, and you can see almost everything that's known. Let's take a look. Here, you can see the up-to-date list of how many of everything there is. You can look at the list. Total confirmed planets. Let's look at all total confirmed planets, and you'll end up with a list of every single one of em. Where they came from, how much they weigh anything else there that you would like to know. I actually like, rather than just going to the list, going to these plots. You go to the plots, you can put in your own parameters, on this side, of what you want to plot and you'll get a plot, scatter plot, histogram, there, there are a million things you can do and learn from doing this. Let's just do a very simple one and let's look at by about the year 2000, which is still pretty early in the exo-planet business. By the year 2000, what were the exo-planets known? How big were they? How far away from their star were they? And I'll let you figure out how to input all these parameters over here but you can now see that I have orbital period, which is a proxy for how far away they are, and I have Msin I, M is the mass of the planet. Sin I is the sign of the inclination. Defined in a funny way where an edge on planet has a 90 degree inclination so the sin of I is one, so you're really measuring the mass. Something in 45, has a 45 degree inclination so you're measuring square root of 2 mass, and something that is straight up and down has a 0 degree inclination, so if you measure anything it has an infinite mass, which doesn't make any sense. What is that parameter that we don't know without the transits? Let's see what we have. Masses over here, we have orbital periods. I was talking about three day orbits. One, two, three. These are some of the first Hot Jupiters. In fact, you can hover over this, and click on any of the points. And see what these are all actually called. And if you click on one of 'em, you get detailed parameters like the velocity, and every possible thing that we know about it. All pretty good stuff. But let's look at this now, we have Msin I, Msin I remember is now the minimum they could be more if they are not edge on but they can't be less. And we have things as high as six Jupiter masses and potentially more. We have things that around ones down in through here, these are normal Jupiter-looking sort of things. But we, again, we have these orbital periods of three, the really Hot Jupiters, 10, 50, 10, 20, 30, 40, 50, that would be Mercury. We have things out to the orbit of the Earth. The orbit of the Earth has 365 days. Here's 100, 200, 365 things like this. All of these things are inside the orbit of the Earth. What we don't have is anything outside of about 10,000 days. We even have a few things that are actually mo, out at something like the 12-year orbital period of Jupiter itself. Now we're not going to go into this in details but these are actually not like Jupiter. Jupiter is a nice beautiful circular orbit around the sun. These things are in crazy, eccentric orbits. In fact, many of these are in crazy, eccentric orbits around their star. Except for these, these are sitting so close that they're in nice, beautiful circular orbits for the most part. And these are the ones that we're going to concern ourselves with now because these are the ones for which the probability of having a transit is the highest. Remember that probability of having a transit simply goes down as the reciprocal of distance away. The further away you are, the less likely that you're going to spend any time directly in front of the star. So these are the ones that are most likely to have the transits, and these are the ones that people watch very closely to see if they're going to be any kind of transits to be found. It's interesting to point out, though, without thinking about the transits very much, the, already the diversity of things you see. You see very massive planets. Where do those very massive planets come from? You could imagine, perhaps, that they came from a very massive disk that somehow had the ability to, to accrete more of a core and get more of a gas. Although you'll remember that the more massive a disk is, the closer it comes to disk instability. So maybe these massive ones are formed not in the same way these are. Maybe these are formed in that instability. These are formed from core accretion. One thing that we would like to learn about these, just like we learned about our own planets, is what do the densities tell us about the materials? Do these have cores? Do these have cores? Let's go look and see what we can find out. Here's a view of mass versus radius, essentially, the density. Of Hot Jupiters, at about 2005. I'm, I'm purposely keeping it to not the most recent results, because the most recent results get overwhelming and we'll talk about those at a separate point. Here's that one where we talked about HD209458B, the very first one detected. And here's that pure hydrogen and helium line. And [COUGH] if you add more material, more heavy material, You're down below this line, like Jupiter is down here. Saturn is down here. How the heck do you get above this line? HD209458B, even though it has some fairly large uncertainties in exactly how big it is. It's something like a factor of two bigger in radius than a pure hydrogen helium atmosphere even would be. It was considered quite surprising when it was discovered after the next few ones were consistent with hydrogen helium consistent with hydrogen helium maybe a little bit high, and a few others up here, and by now there are enough objects up here In the bigger than they should be category that it's clear that something is going on. Interestingly also, you don't have anything down in here in the smaller than pure hydrogen and helium. There's nothing the side of Jupiter, the side of Saturn at least in this initial data. So what's happening? Are these things made out of different material then Jupiter? Well, they could be made out of pure hydrogen. We don't put that on there. It would be a little bit smaller but, but it would be sort of impossible to sort the hydrogen from the helium in the universe. So that's a kind of crazy idea. There's nothing lighter than hydrogen. So there's no way to really sensibly get above this line in a standard planetary interior. So something funny is happening, something funny is happening to make these things what are called inflated [SOUND] Hot Jupiters. We will spend the next lecture learning about these inflated Hot Jupiters, how you can inflate them and how you could potentially use that to once again try to figure out what's going on in the inside of these things. Maybe learn a little bit more about Jupiter too.
