 Fact truly is stranger than fiction. For millennia it was thought that worlds amongst those points of light that occupy our sky were the realms of speculation, pure wild fiction, and even heresy. But as technology got better, turns out, fiction really was fact. This is your space pod for August 14, 2015. It's one of the most exciting subjects in space sciences, exoplanets. They're so hot right now. In fact lots of them are hot, lots of them are cold, some of them are lukewarm as well. Some are big, some are small, but we like exoplanets. They make us excited at the possibility of life off of this planet. And there are also potential places that we may be able to visit when we're capable of reasonably fast interstellar travel. The beginnings of extrasolar planets goes back to 1992, when three planets were discovered to be orbiting a pulsar, a wonderfully named one too, PSR B1257-12. Sounds like my kind of vacation spot. These planets are close enough to the pulsar to be zapped continuously, overall places that life probably won't be. These three planets are a bit of a mystery though, since a pulsar is formed via supernova, the literal rebound of an imploding star. Does this mean these planets survived that immense release of energy? Was there a second round of planet formation? Scientists lean towards the second round hypothesis, but it's still quite an interesting conundrum. In the over two decades since we first confirmed that exoplanets are no longer just a hypothesis that they're an actual thing, we've made a little bit of progress, with most of that coming from the Kepler space telescope. Today, August 14th, 2015, we sit at 1,942 confirmed extrasolar planets. And the data from Kepler has all but confirmed that just about every single star has at least one planet around it during its lifetime. With 400 billion stars in the Milky Way, that means we're pushing a bottom number of 1 trillion planets, and that's just our galaxy. We find these planets primarily through two techniques, radial velocity and transit photometry. The radial velocity method is good for finding out an exact mass of the planet as you're measuring the tug of a planet as it orbits its star. I sometimes like to call it the wiggle method, because we're measuring literally how much distance that planet is moving or wiggling the star that it orbits. Although you can imagine that since we're looking at objects trillion, quadrillion, and even quintillions of kilometers away, this method has its limits. Transit photometry is the method by which a majority of exoplanets are discovered. We measure the amount of light coming from a star, and as a planet moves in front of it, we see the total amount of light coming from that star dipped down, and then come back to normal. This indicates that the planet has transited across the star we see. The Kepler team requires at least three transits of a star before the planet is considered to be confirmed, hence the large numbers of planet candidates yet to be confirmed in Kepler's massive data bank. This technique has yielded the most data, but is limited because the planets must be orbiting on a path that places them directly between their parent star and our view, and you can imagine just how many planets and planetary systems aren't doing that. Thanks for watching this SpacePod. I'm Jared Head. Don't forget to comment, like, and subscribe to us on social media. We also do have a Patreon campaign, so if you've got a little extra and like to see these Space Pods, help us keep them going and contribute a little bit to that. So, until the next SpacePod, keep exploring.