This topic has come up, tangentially, in multiple threads now, and as there's interest but not really a proper place, I figured I would give this a go and see what sort of interest we have in a thread on this, particularly as it's a dynamic field and so there is a lot of opportunity for speculation that doesn't require a strong background on it, as well as discussing the significance of the discoveries being made. Rather than start with a subtopic, I thought I would give an overview of some of the basics first, and then see where the discussion goes from there. Extrasolar Planets (ESP) are, as the name rather indicates, planets outside our solar system. The objects themselves are rather simply objects that are not massive enough to be stars, although there's not presently a lower constraint for objects outside our solar system as to what constitutes a planet. Additionally, all those that have been confirmed are orbiting other stars, although it is possible and likely that there are some that are free floating, although these have not yet been found. Currently, we know of just over 450 ESPs. The primary way that they've been detected (around 350) has been by measuring the radial velocities of host stars. A planet orbiting a star causes the star to wobble back and forth slightly, and so by measuring how fast the star is moving as it heads towards us and away from us, we can get a constraint on the mass of the planet, as well as figure out some values for its orbit. We find that most of the objects we've found this way are around the mass of Jupiter to several times the mass of Jupiter, and with orbits that tend to be only several days long. The second most common detection method is to look for planets that go in front of their star as they orbit, resulting in the star periodically dimming as the planet passes in front of it. This allows us figure out, again, the orbit of the planet, as well as the radius of the planet. When we use this method with the above, it means that we can get both the radius and the mass of the planet, which allows for a much more complete picture. We do find that most of these planets through this method are, again, planets around the mass of Jupiter or higher, and that have orbits that are only a few days long, meaning that these planets are much closer than even Mercury is to our own sun. At least one key factor in why most planets we find have these characteristics, though, is that very massive planets with very short orbits are the easiest to find, and so we do expect the characteristics of the population of known ESP to change over the coming years as we develop better accuracy in our techniques and have more time to observe. That gives a very basic overview of what most of the planets we've found are like and how we're finding them, and I'll leave this at that to then see what areas have the greatest interest to continue onward in.