1 00:00:01,920 --> 00:00:07,320 Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff, 2 00:00:07,360 --> 00:00:11,360 Speaker 1: Lauren bog ol Bomb. Here there's something big lurking in 3 00:00:11,400 --> 00:00:14,200 Speaker 1: the frozen hinterlands of our Solar System that appears to 4 00:00:14,240 --> 00:00:17,239 Speaker 1: be tugging at the tiny worlds beyond the orbit of Neptune. 5 00:00:17,720 --> 00:00:20,279 Speaker 1: The object is assumed to be a hypothetical world called 6 00:00:20,360 --> 00:00:23,599 Speaker 1: Planet nine, which has an extremely far flung orbit around 7 00:00:23,600 --> 00:00:26,360 Speaker 1: the Sun and causes all kinds of gravitational chaos out 8 00:00:26,400 --> 00:00:29,440 Speaker 1: there in the dark. But as the search for Planet 9 00:00:29,480 --> 00:00:31,880 Speaker 1: nine wears on and astronomers have yet to so much 10 00:00:31,880 --> 00:00:34,519 Speaker 1: as get a glimpse of it, some researchers are pondering 11 00:00:34,640 --> 00:00:37,360 Speaker 1: what else the object could be. Might it not be 12 00:00:37,400 --> 00:00:40,920 Speaker 1: a planet at all? Could it be a primordial black hole? 13 00:00:42,400 --> 00:00:44,879 Speaker 1: The Solar System is a big place, and while our 14 00:00:44,920 --> 00:00:48,640 Speaker 1: astronomical techniques are rapidly advancing, many tiny bodies in the 15 00:00:48,640 --> 00:00:51,920 Speaker 1: outer Solar System have yet to be found. Planet nine 16 00:00:51,960 --> 00:00:54,480 Speaker 1: is thought to be a rather more substantial object, however, 17 00:00:54,720 --> 00:00:57,880 Speaker 1: with a massive around five to ten Earth masses scooting 18 00:00:57,920 --> 00:01:00,320 Speaker 1: around the Sun at an average distance of four to 19 00:01:00,480 --> 00:01:04,559 Speaker 1: eight hundred astronomical units or a US, since one AU 20 00:01:04,720 --> 00:01:07,040 Speaker 1: is the average distance at which Earth orbits the Sun. 21 00:01:07,400 --> 00:01:09,839 Speaker 1: That's ten to twenty times the orbital distance at which 22 00:01:09,840 --> 00:01:13,600 Speaker 1: Pluto orbits the Sun, So if it exists, planet nine 23 00:01:13,640 --> 00:01:16,560 Speaker 1: takes between ten thousand and twenty thousand years to complete 24 00:01:16,640 --> 00:01:21,000 Speaker 1: just one orbit. The possibility of a large world orbiting 25 00:01:21,000 --> 00:01:24,320 Speaker 1: the Sun at such a huge distance is captivating. Studies 26 00:01:24,360 --> 00:01:27,360 Speaker 1: of other star systems reveal that exoplanets between the masses 27 00:01:27,360 --> 00:01:31,360 Speaker 1: of Earth and Neptune are relatively common. Why our Solar 28 00:01:31,400 --> 00:01:33,960 Speaker 1: System doesn't contain a world with this mass range is 29 00:01:34,000 --> 00:01:36,760 Speaker 1: a puzzle. But if Planet nine really is out there, 30 00:01:37,000 --> 00:01:39,840 Speaker 1: it would be a profound historic discovery that would reshape 31 00:01:39,840 --> 00:01:42,559 Speaker 1: our understanding of the system of planets that orbit our Sun. 32 00:01:44,040 --> 00:01:46,920 Speaker 1: Suffice to say, any planet with an orbit this extreme 33 00:01:47,000 --> 00:01:50,440 Speaker 1: would be very difficult to spot, but astronomers are scouring 34 00:01:50,520 --> 00:01:53,760 Speaker 1: infrared surveys with hopes of seeing a distant object slowly 35 00:01:53,800 --> 00:01:57,360 Speaker 1: crawl across the sky. If it's out there, planet nine 36 00:01:57,400 --> 00:02:01,080 Speaker 1: should be emitting infrared radiation entered leaking from the planet 37 00:02:01,160 --> 00:02:04,680 Speaker 1: since its formation, but so far, apart from the gravitational 38 00:02:04,720 --> 00:02:07,840 Speaker 1: effects of something in the outer Solar System, there's precious 39 00:02:07,880 --> 00:02:12,239 Speaker 1: little direct evidence for Planet nine existence. Enter the black 40 00:02:12,280 --> 00:02:17,000 Speaker 1: hole hypothesis. In September of twenty nineteen, astronomer's Jacob Schultz 41 00:02:17,000 --> 00:02:19,519 Speaker 1: of Durham University and James Unwin of the University of 42 00:02:19,560 --> 00:02:24,040 Speaker 1: Illinois Chicago published a new study describing their alternative hypothesis 43 00:02:24,240 --> 00:02:26,720 Speaker 1: that the gravitational weirdness in the outermost reaches of the 44 00:02:26,760 --> 00:02:30,720 Speaker 1: Solar System isn't being caused by a planet at all. Instead, 45 00:02:31,000 --> 00:02:34,040 Speaker 1: they pointed to the potential presence of a primordial black hole, 46 00:02:34,400 --> 00:02:37,720 Speaker 1: a theory that's caused a bit of a stir No. 47 00:02:37,960 --> 00:02:40,120 Speaker 1: This kind of black hole does not pose a danger 48 00:02:40,160 --> 00:02:42,040 Speaker 1: to the rest of the Solar System, it would be 49 00:02:42,080 --> 00:02:44,919 Speaker 1: too small for that, but in the distant regions of 50 00:02:44,919 --> 00:02:48,440 Speaker 1: our Solar System its impact would be significant. The only 51 00:02:48,480 --> 00:02:51,359 Speaker 1: evidence we have for Planet nine existence are the gravitational 52 00:02:51,360 --> 00:02:55,120 Speaker 1: effects it's having on trans neptune objects, and black holes 53 00:02:55,120 --> 00:02:58,160 Speaker 1: are the most gravitationally endowed objects in the universe. After all, 54 00:02:59,639 --> 00:03:02,200 Speaker 1: Primal real black holes are the most ancient kind of 55 00:03:02,240 --> 00:03:05,200 Speaker 1: black hole. They're hypothesized to have formed right after the 56 00:03:05,240 --> 00:03:08,920 Speaker 1: Big Bang. Density fluctuations in the early universe would have 57 00:03:09,000 --> 00:03:12,880 Speaker 1: rapidly formed black holes of all masses. These ancient objects 58 00:03:12,880 --> 00:03:15,800 Speaker 1: would have been flung throughout the cosmos, and over time 59 00:03:16,040 --> 00:03:19,839 Speaker 1: they would have slowly evaporated via Hawking radiation, smaller ones 60 00:03:19,880 --> 00:03:24,040 Speaker 1: popping out of existence first. But let's back up a step. 61 00:03:24,520 --> 00:03:27,520 Speaker 1: Why designed to think that some extreme object is out there? 62 00:03:28,240 --> 00:03:33,000 Speaker 1: In planet Hunter's Constantine, Batiguon and Mike Brown of Caltech 63 00:03:33,280 --> 00:03:36,400 Speaker 1: announced their discovery of a group of very distant trans 64 00:03:36,400 --> 00:03:40,320 Speaker 1: Neptunian objects that were all strangely clustered and moving with 65 00:03:40,400 --> 00:03:44,760 Speaker 1: similar orbital alignments. Their orbital alignment was also weirdly tilted, 66 00:03:44,960 --> 00:03:48,200 Speaker 1: so it appeared they were all being corralled by gravitational 67 00:03:48,200 --> 00:03:52,200 Speaker 1: interactions with a larger planetary body. But no other large 68 00:03:52,240 --> 00:03:56,000 Speaker 1: planetary body exists in that region, So Batigan and Brown 69 00:03:56,080 --> 00:03:58,880 Speaker 1: hypothesized than an as get to be discovered planet was 70 00:03:58,920 --> 00:04:03,840 Speaker 1: out there, and so the hunt began. While many theories 71 00:04:03,840 --> 00:04:07,360 Speaker 1: of cosmic evolutions suggest that primordial black holes should exist, 72 00:04:07,760 --> 00:04:10,720 Speaker 1: we have yet to directly observe one, though there is 73 00:04:10,800 --> 00:04:15,160 Speaker 1: some compelling indirect evidence. Take, for example, micro lensing events, 74 00:04:15,480 --> 00:04:18,560 Speaker 1: the transient brightening of stars caused by a massive object 75 00:04:18,680 --> 00:04:21,920 Speaker 1: passing in front of them, causing a brief brightening via 76 00:04:21,960 --> 00:04:24,880 Speaker 1: the curvature of space time, creating a sort of magnifying lens. 77 00:04:25,480 --> 00:04:28,719 Speaker 1: Analysis of these micro lensing events suggests that there's a 78 00:04:28,720 --> 00:04:31,240 Speaker 1: population of small black holes out there with no other 79 00:04:31,320 --> 00:04:35,000 Speaker 1: visible clues except for their gravitational impact on space time. 80 00:04:35,880 --> 00:04:38,480 Speaker 1: Schultzon Unwin took a fresh look at the trans Neptune 81 00:04:38,520 --> 00:04:41,760 Speaker 1: object peculiarities and simulated what would happen if a black 82 00:04:41,800 --> 00:04:44,000 Speaker 1: hole with a mass of between five and ten Earth 83 00:04:44,040 --> 00:04:47,599 Speaker 1: masses had an extreme orbit around the Sun. Sure Enough, 84 00:04:47,800 --> 00:04:50,240 Speaker 1: their models suggest that a primordial black hole with a 85 00:04:50,279 --> 00:04:53,720 Speaker 1: mass within this range would cause orbital perturbances like the 86 00:04:53,720 --> 00:04:57,320 Speaker 1: ones already observed in the population of trans Neptune objects. 87 00:04:58,200 --> 00:05:01,800 Speaker 1: This could also explain why little optical or infrared observational 88 00:05:01,839 --> 00:05:05,440 Speaker 1: evidence for planet nine exists. A primordial black hole would 89 00:05:05,440 --> 00:05:09,200 Speaker 1: generate neither signal. In fact, if a black hole is nearby, 90 00:05:09,279 --> 00:05:11,400 Speaker 1: it may also be dragging around a cloud of dark 91 00:05:11,440 --> 00:05:14,760 Speaker 1: matter that could be generating different types of radiation. The 92 00:05:14,800 --> 00:05:18,719 Speaker 1: researchers therefore suggest, based on their findings, that the experimental 93 00:05:18,720 --> 00:05:22,359 Speaker 1: program needs to be expanded, including searches for high energy 94 00:05:22,400 --> 00:05:25,320 Speaker 1: cosmic rays like X rays and gamma rays coming from 95 00:05:25,320 --> 00:05:29,040 Speaker 1: moving sources. While this is an interesting avenue of study, 96 00:05:29,320 --> 00:05:32,440 Speaker 1: replacing a hypothetical planet with a hypothetical type of black hole, 97 00:05:32,960 --> 00:05:36,919 Speaker 1: maybe over complicating the mystery of planet nine. We spoke 98 00:05:36,960 --> 00:05:40,280 Speaker 1: with Mike Brown. He said, could a black hole explain 99 00:05:40,320 --> 00:05:43,720 Speaker 1: the gravitational effects we are seeing in the outer Solar System? Absolutely? 100 00:05:44,200 --> 00:05:46,240 Speaker 1: All we know is that there is a six earth 101 00:05:46,320 --> 00:05:48,960 Speaker 1: mass something out there, and we don't know what the 102 00:05:49,000 --> 00:05:52,640 Speaker 1: something is. Brown points out that a planet would be 103 00:05:52,640 --> 00:05:55,680 Speaker 1: the most obvious something, but as long as it has 104 00:05:55,680 --> 00:05:57,880 Speaker 1: a mass of a few earths, it could be anything. 105 00:05:58,480 --> 00:06:00,720 Speaker 1: But the plausibility of it being an anything other than 106 00:06:00,720 --> 00:06:03,800 Speaker 1: a planet is extremely low, to say the least. With 107 00:06:03,880 --> 00:06:06,160 Speaker 1: tongue in cheek, Brown added, it might be a six 108 00:06:06,160 --> 00:06:09,520 Speaker 1: earth mass hamburger or a burrito, but yes, it might 109 00:06:09,560 --> 00:06:12,520 Speaker 1: also be a six earth mass black hole. The physics, 110 00:06:12,600 --> 00:06:14,680 Speaker 1: of course, don't care one bit what the six earth 111 00:06:14,680 --> 00:06:17,680 Speaker 1: masses are made of. You could equally well hypothesize that 112 00:06:17,720 --> 00:06:20,479 Speaker 1: every exoplanet that we only detect via the radial velocity 113 00:06:20,520 --> 00:06:23,840 Speaker 1: method is a black hole. Is it possible? Yes? Does 114 00:06:23,839 --> 00:06:28,560 Speaker 1: it make any sense in the universe? No. While investigating 115 00:06:28,560 --> 00:06:31,800 Speaker 1: other gravitational sources of what may be messing with transniptune 116 00:06:31,839 --> 00:06:35,080 Speaker 1: objects is good science, it's more likely the planet nine 117 00:06:35,160 --> 00:06:38,960 Speaker 1: is a planet and not a primordial black hole. Astronomers 118 00:06:39,000 --> 00:06:41,720 Speaker 1: just have to keep searching, and there's a growing consensus 119 00:06:41,720 --> 00:06:44,080 Speaker 1: that it will be discovered in the not so distant future. 120 00:06:44,400 --> 00:06:51,920 Speaker 1: We'll keep you updated. Today's episode was written by Dr 121 00:06:51,960 --> 00:06:54,880 Speaker 1: Ian O'Neill and produced by Tyler Klang. Brain Stuff is 122 00:06:54,920 --> 00:06:57,360 Speaker 1: production of I Heart Radio's How Stuff Works. For more 123 00:06:57,400 --> 00:06:59,480 Speaker 1: on this and lots of other topics that are surprisingly 124 00:06:59,520 --> 00:07:02,000 Speaker 1: dense for their size, visit our home planet, how stuff 125 00:07:02,000 --> 00:07:04,880 Speaker 1: Works dot com. And for more podcasts from my heart Radio, 126 00:07:05,160 --> 00:07:07,800 Speaker 1: visit the heart Radio app, Apple Podcasts, or wherever you 127 00:07:07,839 --> 00:07:09,000 Speaker 1: listen to your favorite shows.