Everything Everywhere Daily: History, Science, Geography & More - Planet X

Starting point is 00:00:00 Ever since the discovery of the planet Neptune in 1846, astronomers have noticed that something wasn't right. The orbit of Neptune was being gravitationally influenced by some other unknown body that was dubbed Planet X. In 1930, it was thought that this body had been discovered with the discovery of Pluto, but that couldn't have been the object that was influencing Neptune because it was far too small. The search for this mysterious object has continued to this day, and some astronomers think that we're finally close to finding it. Learn more about the hunt for Planet X, aka Planet 9, on this episode of Everything Everywhere Daily.

Starting point is 00:00:38 What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now. Time travel with us. every week on the ThuLine podcast from NPR. Planet X sounds like something from a 1950s science fiction novel, but it's not.

Starting point is 00:01:23 This episode is not about space aliens from Planet X. Planet X is a very real thing, or to be more accurate, it's a very real hypothesis. Many top astronomers have been hunting for planet X for decades. The story of Planet X begins in the 18th century with the discovery of urine. If you remember back to my episode on it, Uranus was discovered in 1781 by William Herschel. Finding a planet beyond those known since antiquity was a major astronomical discovery. By the time of the discovery of Uranus, the basic of orbits had been firmly established. Once the discovery was announced, other observations were made, and there was a problem.

Starting point is 00:02:07 The orbital path of Uranus wasn't quite what it was supposed to be. It didn't follow the orbit predicted by Newton's laws of motion, which suggested that there was some other planet which was acting on it. In 1846, French mathematician Urbane Laviere calculated the position of this unseen planet using the discrepancies in Uranus's orbit. Independently and almost simultaneously, the British mathematician John Couch Adams made similar calculations. Based on Lavier's predictions, the German astronomer Johann Gottfried Gala observed

Starting point is 00:02:41 Neptune for the first time on September 23, 1846, just one degree from where La Vieer had predicted it to be. The prediction of Neptune before it was discovered was a massive triumph for mathematics. However, there was still a problem. The orbit of Uranus still couldn't be totally explained by Neptune, and there were deviations in the order of Neptune that couldn't be explained. That implied that there was something else that was still out there that had to account for the orbital discrepancies. So, astronomers once again set out to find whatever it was that was influencing the orbit of Neptune. One of the leaders in the hunt was a Boston businessman named Percibel Lovel. He dubbed this mystery planet, Planet X. He established an observatory in Arizona named the Lowell Observatory,

Starting point is 00:03:31 which, among its many projects, focused on the discovery of Planet X. After years of the of searching for something. In 1930, they found something. Astronomer Clyde Tomba, after comparing photographic plates, found something moving. That moving object in the distant solar system was dubbed Pluto. The initial assumption was that they had discovered Planet X. However, as more was learned about Pluto, there was a problem. Pluto was far too small to account for the orbital discrepancies in Neptune. It was so small, it couldn't even be observed as a disc. It was just a point of light. From the moment it was discovered, the estimates of the mass of Pluto were continuously estimated downward as we learned more

Starting point is 00:04:18 about it. It was initially thought to be about the same size as the Earth, and now it's thought to only be about one-fifth of 1% the mass of the Earth. The Planet X theory fell out of favor in the 1970s and 1980s, especially after the Voyager 2 spacecraft was able to make a more accurate measurement of the mass of Neptune. However, the idea of Planet X came back into vogue in the early 2000s with the discovery of Sedna. Sedna doesn't get a lot of attention, but it was a really important discovery. Sedna was a large object beyond the orbit of Pluto.

Starting point is 00:04:55 It wasn't as large as Pluto, but it really brought home the issue of what is a planet that eventually led to the demotion of Pluto as a planet. It also brought back the idea of Planet X because of Sedna's extremely eccentric orbit. Pluto had a very eccentric orbit, but it was nothing like Sedna. At its closest point to the sun, Sedna is 76 astronomical units from the sun. An astronomical unit is the average distance from the Earth to the sun. At its furthest point, Sedna is 937 astronomical units from the sun. Sedna wasn't the only trans-Neptunian body that was discovered that had such an exaggerated orbit.

Starting point is 00:05:36 In 2012, another body was discovered known as 2012 v.P. 113. In 2015, an object known as Liliaku Hanua was discovered that has an even more elongated orbit than Sedna. At its closest point, Laliaku Hanua is 65 astronomical units from the sun, and at its furthest point, it's 2,126 astronomical units from the Sun. The problem is that these orbits make absolutely no sense. They can't be explained by the gravitational pull of the major known planets in the solar system. Likewise, it couldn't be galactic tides. These are the gravitational poles which come from the gravitational fields of a galaxy,

Starting point is 00:06:18 like the Milky Way. If they had been formed in their current location, they would have been circular orbits like the planets. This is because of how accretion works when smaller objects form larger ones. If there were massive differences in velocity or direction, then it never would have been formed. That means that something else must have caused the extreme orbits of these bodies. There have been several theories put forward as to what might have caused this. The first theory is that early in the birth of the solar system, the sun may have been born in what is known as a star nursery.

Starting point is 00:06:52 During this period, another star may have come close to the star. Sun, relatively speaking, and that would have been enough to have influenced the orbits of these distant objects. The second theory is that Sedna and other similar objects didn't even originate around the sun. During the formation of the sun, the objects may have been captured by the sun, having been jettisoned from some other solar system. And the other theory, the one that has gained the most support, is that there is a distant, massive object in the solar system that is responsible for causing their highly elongated orbits. Basically, a return to the Planet X hypothesis that existed back in the late 19th and early 20th centuries. The evidence for Planet X is more than just the fact that

Starting point is 00:07:36 these planetoids have highly elliptical orbits. Their orbits also tend to be clustered. Instead of each object clearing out a space, you see a lot of them clumped together. And finally, most of these objects have highly inclined orbits. The eight planets in the solar system are all basically in what is known as the ecliptic plane. These extreme trans-Neptunian objects, however, go well outside the ecliptic plane at steep angles to the rest of the planets. The Planet X hypothesis has gained traction because it explains all of the things about the orbits of these objects that I've just listed. The quest of find Planet X has been a much more advanced version of the discovery of Neptune. Neptune was discovered with mathematics before it was ever

Starting point is 00:08:20 observed with a telescope. As more trans-Neptunian objects are discovered and their orbits calculated, it's possible to use computers to calculate data about possible orbits for planet X. Computer simulations have been able to recreate similar results to what we see today with a heavy planet in a very distant orbit. As a result, many astronomers believe that they are narrowing down possible locations where planet X might be found. That is, if it exists. So what would planet X look like if it indeed does exist? It would probably be something larger than Earth, but smaller than Neptune. The current best guess is that it would be 6.2 times the mass of the Earth. It would likely have an orbit that would be slightly elliptical, more elliptical than the planets,

Starting point is 00:09:09 but less so than Sedna and other similar objects. Likewise, it would be about 11 to 20 degrees inclined to the ecliptic plane. Again, more than the planets, but much less than other objects at that distance. Moreover, its orbit would take it anywhere from 240 to 500 astronomical units from the sun. So if planet X can explain many of the questions regarding Sedna and other trans-Neptunian objects, and if we can compute its possible orbit and even its mass, then the big question is, where is it? The problem with trying to find a planet that is that far away is that it's almost impossible to see. Planets, unlike stars, do not produce light. They can only reflect light. Planets that are closer to the sun reflect more light. That's why Venus looks

Starting point is 00:10:01 so bright in the sky, almost as if it were a star. However, once you're beyond the orbit of Neptune, it's hard to get enough light. From the distance that planet X would have to be, it would be extremely dim. In fact, the sun would appear as nothing other than the brightest star in the sky from the surface of planet X. With so little light reaching the planet and even much less light being reflected back, planet X would be extremely difficult to observe. It would be difficult to detect amongst all of the background stars in the galaxy. It would require viewing photographic images of the same point in the sky at different times and seeing if anything had moved. Even if we could identify it, it probably would appear as nothing more than a point of light, or maybe a small

Starting point is 00:10:47 disc with no details, even from the most powerful telescopes. The good news is that astronomers think that they're getting close to finding planet X, or at least they're narrowing down where to look for it. However, in all fairness, there are also still astronomers who are skeptical, and they don't think that there is a planet X. So what if we do find Planet X, with the recent controversy surrounding the demotion of Pluto as a planet, would Planet X even be considered an actual planet? Well, it would depend on what we can find out about it. If it's more massive than Earth, then it probably would be considered a planet. The reason why Pluto was demoted is because it wasn't massive enough to clean out its orbit of other debris. The only other reason why it might

Starting point is 00:11:34 not be considered a planet, despite its large landmass, would be because of its very long orbit. The hunt for Planet X has been going on for decades now. While there is optimism in some circles that the planet will soon be found, that optimism is not universal. Nonetheless, one day you might wake up to find that there are once again nine planets in the solar system. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Benji Long and Cameron Kiever.

Starting point is 00:12:06 I want to give a big shout out to everyone who supports the show over on Patreon, including the show's producers. Your support helps me put out a show every single day. And also, Patreon is currently the only place where Everything Everywhere daily merchandise is available to the top tier of supporters. If you'd like to talk to other listeners of the show and members of the Completionist Club, you can join the Everything Everywhere Daily Facebook group or Discord server. Links to everything are in the show notes.

Everything Everywhere Daily: History, Science, Geography & More - Planet X

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