Speaker 1: Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,
Speaker 1: Lauren bog ol Bomb. Here there's something big lurking in
Speaker 1: the frozen hinterlands of our Solar System that appears to
Speaker 1: be tugging at the tiny worlds beyond the orbit of Neptune.
Speaker 1: The object is assumed to be a hypothetical world called
Speaker 1: Planet nine, which has an extremely far flung orbit around
Speaker 1: the Sun and causes all kinds of gravitational chaos out
Speaker 1: there in the dark. But as the search for Planet
Speaker 1: nine wears on and astronomers have yet to so much
Speaker 1: as get a glimpse of it, some researchers are pondering
Speaker 1: what else the object could be. Might it not be
Speaker 1: a planet at all? Could it be a primordial black hole?
Speaker 1: The Solar System is a big place, and while our
Speaker 1: astronomical techniques are rapidly advancing, many tiny bodies in the
Speaker 1: outer Solar System have yet to be found. Planet nine
Speaker 1: is thought to be a rather more substantial object, however,
Speaker 1: with a massive around five to ten Earth masses scooting
Speaker 1: around the Sun at an average distance of four to
Speaker 1: eight hundred astronomical units or a US, since one AU
Speaker 1: is the average distance at which Earth orbits the Sun.
Speaker 1: That's ten to twenty times the orbital distance at which
Speaker 1: Pluto orbits the Sun, So if it exists, planet nine
Speaker 1: takes between ten thousand and twenty thousand years to complete
Speaker 1: just one orbit. The possibility of a large world orbiting
Speaker 1: the Sun at such a huge distance is captivating. Studies
Speaker 1: of other star systems reveal that exoplanets between the masses
Speaker 1: of Earth and Neptune are relatively common. Why our Solar
Speaker 1: System doesn't contain a world with this mass range is
Speaker 1: a puzzle. But if Planet nine really is out there,
Speaker 1: it would be a profound historic discovery that would reshape
Speaker 1: our understanding of the system of planets that orbit our Sun.
Speaker 1: Suffice to say, any planet with an orbit this extreme
Speaker 1: would be very difficult to spot, but astronomers are scouring
Speaker 1: infrared surveys with hopes of seeing a distant object slowly
Speaker 1: crawl across the sky. If it's out there, planet nine
Speaker 1: should be emitting infrared radiation entered leaking from the planet
Speaker 1: since its formation, but so far, apart from the gravitational
Speaker 1: effects of something in the outer Solar System, there's precious
Speaker 1: little direct evidence for Planet nine existence. Enter the black
Speaker 1: hole hypothesis. In September of twenty nineteen, astronomer's Jacob Schultz
Speaker 1: of Durham University and James Unwin of the University of
Speaker 1: Illinois Chicago published a new study describing their alternative hypothesis
Speaker 1: that the gravitational weirdness in the outermost reaches of the
Speaker 1: Solar System isn't being caused by a planet at all. Instead,
Speaker 1: they pointed to the potential presence of a primordial black hole,
Speaker 1: a theory that's caused a bit of a stir No.
Speaker 1: This kind of black hole does not pose a danger
Speaker 1: to the rest of the Solar System, it would be
Speaker 1: too small for that, but in the distant regions of
Speaker 1: our Solar System its impact would be significant. The only
Speaker 1: evidence we have for Planet nine existence are the gravitational
Speaker 1: effects it's having on trans neptune objects, and black holes
Speaker 1: are the most gravitationally endowed objects in the universe. After all,
Speaker 1: Primal real black holes are the most ancient kind of
Speaker 1: black hole. They're hypothesized to have formed right after the
Speaker 1: Big Bang. Density fluctuations in the early universe would have
Speaker 1: rapidly formed black holes of all masses. These ancient objects
Speaker 1: would have been flung throughout the cosmos, and over time
Speaker 1: they would have slowly evaporated via Hawking radiation, smaller ones
Speaker 1: popping out of existence first. But let's back up a step.
Speaker 1: Why designed to think that some extreme object is out there?
Speaker 1: In planet Hunter's Constantine, Batiguon and Mike Brown of Caltech
Speaker 1: announced their discovery of a group of very distant trans
Speaker 1: Neptunian objects that were all strangely clustered and moving with
Speaker 1: similar orbital alignments. Their orbital alignment was also weirdly tilted,
Speaker 1: so it appeared they were all being corralled by gravitational
Speaker 1: interactions with a larger planetary body. But no other large
Speaker 1: planetary body exists in that region, So Batigan and Brown
Speaker 1: hypothesized than an as get to be discovered planet was
Speaker 1: out there, and so the hunt began. While many theories
Speaker 1: of cosmic evolutions suggest that primordial black holes should exist,
Speaker 1: we have yet to directly observe one, though there is
Speaker 1: some compelling indirect evidence. Take, for example, micro lensing events,
Speaker 1: the transient brightening of stars caused by a massive object
Speaker 1: passing in front of them, causing a brief brightening via
Speaker 1: the curvature of space time, creating a sort of magnifying lens.
Speaker 1: Analysis of these micro lensing events suggests that there's a
Speaker 1: population of small black holes out there with no other
Speaker 1: visible clues except for their gravitational impact on space time.
Speaker 1: Schultzon Unwin took a fresh look at the trans Neptune
Speaker 1: object peculiarities and simulated what would happen if a black
Speaker 1: hole with a mass of between five and ten Earth
Speaker 1: masses had an extreme orbit around the Sun. Sure Enough,
Speaker 1: their models suggest that a primordial black hole with a
Speaker 1: mass within this range would cause orbital perturbances like the
Speaker 1: ones already observed in the population of trans Neptune objects.
Speaker 1: This could also explain why little optical or infrared observational
Speaker 1: evidence for planet nine exists. A primordial black hole would
Speaker 1: generate neither signal. In fact, if a black hole is nearby,
Speaker 1: it may also be dragging around a cloud of dark
Speaker 1: matter that could be generating different types of radiation. The
Speaker 1: researchers therefore suggest, based on their findings, that the experimental
Speaker 1: program needs to be expanded, including searches for high energy
Speaker 1: cosmic rays like X rays and gamma rays coming from
Speaker 1: moving sources. While this is an interesting avenue of study,
Speaker 1: replacing a hypothetical planet with a hypothetical type of black hole,
Speaker 1: maybe over complicating the mystery of planet nine. We spoke
Speaker 1: with Mike Brown. He said, could a black hole explain
Speaker 1: the gravitational effects we are seeing in the outer Solar System? Absolutely?
Speaker 1: All we know is that there is a six earth
Speaker 1: mass something out there, and we don't know what the
Speaker 1: something is. Brown points out that a planet would be
Speaker 1: the most obvious something, but as long as it has
Speaker 1: a mass of a few earths, it could be anything.
Speaker 1: But the plausibility of it being an anything other than
Speaker 1: a planet is extremely low, to say the least. With
Speaker 1: tongue in cheek, Brown added, it might be a six
Speaker 1: earth mass hamburger or a burrito, but yes, it might
Speaker 1: also be a six earth mass black hole. The physics,
Speaker 1: of course, don't care one bit what the six earth
Speaker 1: masses are made of. You could equally well hypothesize that
Speaker 1: every exoplanet that we only detect via the radial velocity
Speaker 1: method is a black hole. Is it possible? Yes? Does
Speaker 1: it make any sense in the universe? No. While investigating
Speaker 1: other gravitational sources of what may be messing with transniptune
Speaker 1: objects is good science, it's more likely the planet nine
Speaker 1: is a planet and not a primordial black hole. Astronomers
Speaker 1: just have to keep searching, and there's a growing consensus
Speaker 1: that it will be discovered in the not so distant future.
Speaker 1: We'll keep you updated. Today's episode was written by Dr
Speaker 1: Ian O'Neill and produced by Tyler Klang. Brain Stuff is
Speaker 1: production of I Heart Radio's How Stuff Works. For more
Speaker 1: on this and lots of other topics that are surprisingly
Speaker 1: dense for their size, visit our home planet, how stuff
Speaker 1: Works dot com. And for more podcasts from my heart Radio,
Speaker 1: visit the heart Radio app, Apple Podcasts, or wherever you
Speaker 1: listen to your favorite shows.