'Oumuamua's mystery is finally solved!

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Spoiler alert - part of an exo-planet. I doubt the SOLVED nomenclature is warranted.

👍︎︎ 13 👤︎︎ u/shillyshally 📅︎︎ Apr 01 2021 🗫︎ replies

And by "solved", they mean a hypothesis has been proposed that fits the (meager) observations.

👍︎︎ 3 👤︎︎ u/OvertheRedCedar 📅︎︎ Apr 01 2021 🗫︎ replies

Holy crap, it's not someone being edgy and saying it's aliens

👍︎︎ 2 👤︎︎ u/Planet_Nein_ 📅︎︎ Apr 01 2021 🗫︎ replies

TLDW: Its "weird" behavior can be explained by it being made of nitrogen ice.

👍︎︎ 1 👤︎︎ u/LeMAD 📅︎︎ Apr 01 2021 🗫︎ replies
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This video is sponsored by Magellan TV. Welcome  to Launch Pad, I'm Christian Ready, your friendly   neighborhood astronomer. In 2017, 'Oumuamua  became the first observed interstellar object to   pass through our Solar System. That alone would  have made it one for the books, but it didn't   behave like anything we'd seen before. Several  ideas were put forward to explain its origin,   including as a chunk of hydrogen ice, a giant  fractal snowflake, and even a discarded lightsail. But none of these satisfactorily  explained Omamo's origin. Especially the alien lightsail. Sorry. But  now a team of astronomers may have finally   figured it all out. 'Oumuamua wasn't exotic  at all, it was just a fragment of nitrogen   ice that was shattered from an icy Pluto-like  dwarf planet in a young star system in the   Perseus arm of the Galaxy. and ejected into  interstellar space half a billion years ago. OK, that does sound kind of exotic. But as  we'll see, this new analysis not only explains   'Oumuamua's origin and strange behavior, but  suggests that these kinds of objects may be more   common than previously thought. In other words,  'Oumuamua, maybe the first detection of a sample   of an exoplanet brought to us. So today we're  going to talk about how 'Oumuamua's origin can   be explained as a chip off the old exo-Pluto, but  first I would like to thank Magellan TV, who are   very kindly sponsoring today's video. Magellan  curates award-winning documentaries on history,   art, nature and of course space and science. For  example, "Planet Hunters: the Search for Earth's   Twin" talks about the search for a planet just  like ours, with the right size, the right orbit   around its star, and temperatures that are  neither too hot nor too cold to support life.   New programs are added weekly and can be watched  on Roku, Amazon Fire TV, Apple TV, Google Play,   and iOS. And now Magellan is offering  my viewers 30% off an annual membership.   Even better, this offer is available for  both new and returning members alike! So,   if you've been watching along with me, but let  your subscription lapse, Magellan has you covered.   Simply click on the link in the description to  claim your discounted annual membership today. 'Oumuamua was discovered in October  2017. It had already made its closest   approach to the Sun and was heading  out from the inner Solar System.   Working backward, it was clear  that it was on a hyperbolic orbit. In other words, it came from interstellar space  and buzzed the Sun, never to return. What an   exciting observation that was! I mean, it was our  first recorded interstellar object! But everything   about 'Oumuamua just seem to defy explanation. Its  light curve suggested it was shaped either like   a cigar or a pancake with axis ratios between 5:1  all the way up to 10:1. Even the hamburger-shaped   Ultima Lobe of Arrokoth has an axis ratio of about  2:1, and that was considered surprisingly flat.   'Oumuamua's access ratio, at the very  least, was more than twice as extreme.   When the Spitzer Space Telescope tried to observe  'Oumuamua in the infrared. It didn't see anything,   and that meant 'Oumuamua couldn't have been  more than a couple of 100 meters across,   or else Spitzer would have  picked up its thermal emission. But in order to be that small and  still be visible in optical telescopes,   it had to be very reflective. That  is, it needed to have a high albedo. But the weirdest thing about  'Oumuamua was that it actually   gained acceleration as it  was leaving the Solar System. Now to be clear, 'Oumuamua was slowing  down as it was escaping the Suns gravity,   but it wasn't slowing down enough. And, it  was also moving off of its predicted course   as if something were pushing on it. This extra  push is called "non-gravitational acceleration".   It's fairly common with comets, which emit  jets of gas and dust when warmed by the Sun. These jets, act aslow thrust rockets  and give comets a little extra push.   But as if to demonstrate that  'Oumuamua was not a comet,   a second interstellar visitor - 2I/Boriov was  discovered in August of 2019. This object was   very much a comet. The only thing that gave away  its interstellar origin was its hyperbolic orbit. The fact that these two objects were  discovered within two years of each other   implies they must be part of a population  of perhaps millions of interstellar objects   passing through the Solar System. But  while Borisov was very much a comment,   'Oumuamua was very much not, and it wasn't  an asteroid either. It was a thin, broad,   shiny, reddish, tumbling object that somehow  accelerated on its way out of the Solar System. So, researchers considered alternative  hypotheses to explain its strange behavior.   Shmuel Bialy and Avi Loeb showed that 'Oumuamua's  tumbling, acceleration, and lack of outgassing   could be explained if it wasn't a natural  object at all, but rather a discarded lightsail. Made by aliens. Now I would love it if that was the case. I  mean aliens, right? How cool would that be?   But it's not a very convincing hypothesis for a  number of reasons. Among them is that it seems   pretty unlikely that the very first interstellar  object we discover just happens to be an   alien lightsail. Besides, the door was still wide  open for natural, if unconventional explanations.   For example, Amaya Moro-Martín  showed that sunlight pressure   would accelerate 'Oumuamua if  it were a fractal snowflake. Such flakes are thought to form in the outer  regions of protoplanetary disks where it's cold   enough, but it's not clear if fractal snowflakes  could survive ejection from their parents systems,   or collisions with interstellar dust  grains, or even just spinning up to   'Oumuamua's observed rotation rate. So other  researchers considered a different approach:   perhaps. 'Oumuamua was a large fragment of ice? When ice is exposed to sunlight  in dry conditions, it sublimates,   going straight from a solid to a gas space is  very dry. As ice sublimates off the surface,   it would act as a weak thruster and  'Oumuamua would accelerate in response. Darryl Seligman and Gregory  Laughlin considered hydrogen ice.   Hydrogen sublimates very rapidly, so even  a little bit gives a lot of acceleration. They found that of hydrogen ice covered just  6% of 'Oumuamua's surface, it would provide   the observed acceleration. However, hydrogen  freezes at 14 Kelvin. Such temperatures are   only reached in the cores of dense molecular  clouds where starlight never penetrates. It's   not clear how an object gets ejected from such an  environment, or even how it retains its ice once   exposed to the interstellar medium, but perhaps  other kinds of ices would explain 'Oumuamua. To that end, Alan Jackson and Steven Desch  developed a sophisticated model to calculate the   rates of mass loss and corresponding acceleration  on a pancake-shaped, oblate spiroid. As an aside,   many astronomers think, 'Oumuamua was probably  pancake-shaped because a cigar 'Oumuamua would   have to have had a very specific spin orientation  to reproduce the observed light curve. A pancake   on the other hand, can create the observed  light curve over a wider range of orientations. So chances are that 'Oumuamua is likely  pancake-shaped, with access ratios of about 6:1. Jackson and Desch calculated the acceleration  for different kinds of ices over a range of   size and albedo combinations. In other words,  'Oumuamua could have been small and shiny,   or it could have been larger and darker. Only,  not too large or else Spitzer would have seen it. Then they compared the computed accelerations  to 'Oumuamua's observed acceleration. Water, CO2, ammonia, and oxygen ices  were immediately ruled out because   they couldn't accelerate 'Oumuamua fast enough.  By contrast, hydrogen ice provides so much   acceleration that 'Oumuamua would have had to  have been very small with an albedo close to 1. Neon sublimates at just 9 kelvin,   so 'Oumuamua would have lost its neon ice  long before it arrived in the solar system. Carbon monoxide is ruled out because  its sublimation temperature is high   enough that Spitzer likely would have seen it. Methane ices are a thing and  we've detected them on Pluto   in trace amounts. And the methane we did  find on Pluto was dissolved in nitrogen ice. But nitrogen ice, on the other hand,  exists in large quantities on Pluto.   In fact, the large Sputnik Basin is a seaC of  rolling dunes of nitrogen ice. It's also found   on Neptune's moon, Triton, and in other Kuiper  belt objects. And it can give 'Oumuamua the right   acceleration in two circumstances. The first  is if 'Oumuamua had a slightly larger radius,   but a low albedo of 0.1, the second is a  smaller radius and a higher albedo of 0.64. Remarkably, this higher albedo is very  close to those of Pluto and Triton,   our Solar System's very own nitrogen  ski resorts! But all of this raises   an important question: would nitrogen  ice survive a close flyby of the Sun?   The find out Jackson and Desch modeled  'Oumuamua's close encounter. At perihelion,   'Oumuamua closed to within 0.255 AU. That's a  quarter of the distance from the Earth to the Sun. At that distance, 'Oumuamua would have  lossed nitrogen ice at a very high rate.   However, evaporating ice carries away heat  and actually cools the ice left behind.   This is a phenomenon called "evaporative cooling.  Despite being closer to the Sun than Mercury.   'Oumuamua's surface temperature remained closer  to Pluto's. but keeping cool came at a very high   cost. By the time 'Oumuamua was discovered,  it was down to just 8% of its original mass. However, this dramatic loss of ice is  what gave, 'Oumuamua its extreme shape.   Prior to the encounter, 'Oumuamua  would have been larger and thicker,   with an axis ratio of around 2:1. As it lost mass  it shrank and its axis ratio became more extreme,   going all the way up to 6:1. In  other words, it became smaller   and thinner, much like the way a bar of soap  turns into a thin sliver as it's used over time. Even after it past the Sun,  it continued to lose mass,   albeit at a slower rate, just enough to  give 'Oumuamua its observed acceleration. Jackson and Ash even wondered if 'Oumuamua might  have lost some of its ice before the encounter   while it was still in interstellar space.  They found that Galactic Cosmic Rays   would erodes the ice by a significant amount.  Cosmic Rays are charged particles like hydrogen   and helium nuclei that are accelerated  to the 10 to 100 mega electronvolt range.   That's enough to erode nitrogen ice at an  average rate of 6 1/2 meters per billion years. However, that's just the rate of Cosmic Ray  erosion in the Sun's neighborhood today.   Currently the Sun lives between two spiral arms  of the Galaxy. Spiral arms are where stars form   and star forming regions can generate  about four times as many Cosmic Rays.   Over a billion years, 'Oumuamua likely  would have passed through at least one,   perhaps two spiral arms. During those periods,  'Oumuamua would have lost ice twice as rapidly.   On top of that, star formation was much  higher in the past than it is today. The Galaxy experienced multiple surges of  star formation over the last 8 billion years,   probably due to repeated collisions  with the Sagittarius dwarf Galaxy.   Each wave of star formation would  have increased the flux of Cosmic Rays   throughout the Galaxy before settling  down to the present day rate. Our Solar System formed four and a half billion  years ago. If 'Oumuamua were the same age,   it would have lost about 260 meters  of nitrogen ice along the large axes.   That's a lot of ice! But how long was  'Oumuamua really wandering through space? Well,   nobody knows for sure, but its velocity  suggests it probably wasn't that long. Given 'Oumuamua's exit velocity from our Solar  System, astronomers were able to backtrack its   path and work out that while it was traveling  through interstellar space, it couldn't have been   moving at more than about 9 kilometers per second.  That's comparable to the velocities of young stars   within the Galaxy. So, 'Oumuamua was likely  ejected out of a young planetary system, which   means it couldn't have been traveling through the  Galaxy for more than 2 billion years at the most. Two billion years is long enough  for 'Oumuamua to have made several   spiral arm crossings and lose  a lot of mass in the process.   So much that it would have had to have lost  90% of its mass just to reach the Solar System. And that's not impossible, but it seems kind  of unlikely. On the other hand, Jackson and   Desch found that if 'Oumuamua were ejected  half a billion years ago, it only would have   needed to have lost roughly half its mass. That's  still a lot, but it's a little more plausable. So a fragment of nitrogen ice that shrank down to  45 by 44 by 7 1/2 meters at the time of discovery   would explain 'Oumuamua's albedo,  its non-gravitational acceleration,   and its lack of carbon monoxide, CO2, or dust. And nitrogen ice is not particularly  rare. We have plenty of it right here   in the Solar System. 'Oumuamua might  be uncommon, but it's hardly exotic.   It's probably just a fragment of an exo-Pluto.   But how does a fragment of an exo-Pluto get  chucked into interstellar space in the 1st place?   Well, Jackson and Desch published a second paper  that investigates this in considerable detail. Overachievers. They started by considering the history of our  Solar System. Models show that billions of years   ago, the primordial Kuiper belt was much more  massive, totaling about 35 Earth masses. But   interactions with giant planets - I'm  looking at you, Jupiter - ejected most   of this mass into the Oort cloud, and even into  interstellar space. Today's Kuiper Belt is around   1/10th of 1% of its original mass. That means  the primordial Kuiper belt would have had about   3000 Pluto sized objects and millions more  regular Kuiper belt objects, or "KBOs". The migration of the giant planets turned  the Kuiper Belt into a demolition Derby,   with Plutos and KBOs hurtling into each other,  shattering into small fragments of ice. We have   evidence of these kinds of collisions. Pluto's  Sputnik plains - you know, the one filled with   nitrogen ice - is likely an impact basin that  formed in a collision with another small body.   That impact would have liberated  large chunks of nitrogen ice. Many of the fragments would have collided  with other bodies and shattered into even   smaller pieces that would just evaporate  in the sunlight as they swung past Jupiter.   But most of the survivors would be ice  fragments around 50 meters in diameter,   half of which were made of nitrogen and the other  half water ice. The rest would be larger comets   and they would settle into the ORT cloud or be  ejected into interstellar space, never to return. Now that's just the early  history of our Solar System,   but we've seen evidence of planetary migration  and scattering in other systems. For example,   a "Planet Nine" was discovered in the  outskirts of a protoplanetary disk,   presumably after a close encounter with  the binary star system at its center. Such migrations and the resulting scattering are  likely very common in young planetary systems.   Jackson and Desch estimate that our Solar System  likely ejected around 100 trillion ice fragments   alone. That would mean interstellar space  is teeming with ice fragments and comets   thrown out of their planetary systems. Nitrogen  ice fragments would be the most vulnerable to   Cosmic Rays; most of them might only  survive for about a billion years, whereas   water ice fragments fare a little better,  surviving for around 3 billion years. Now given their lower survival rate,   nitrogen fragments might make up just 10% of  the fragments reaching our Solar System. But   nitrogen ice has a much higher albedo  than water, so it's easier to detect. Comets are even more rare because they  are more massive, an harder to toss out   of their home systems. But they're also  larger and brighter and are therefore   easier to detect. So perhaps then,  it's not surprising that the first   two interstellar objects we discovered  was a nitrogen ice fragment and a comet. If 'Oumuamua were ejected half billion years ago  and was traveling at a rate of nine kilometers   per second, then it would've traversed over 3.6  kiloparsecs of the Galaxy. Given that distance and   its direction of approach, it likley originated  somewhere in the Perseus arm of the Galaxy,   which just happens to host a  number of young star systems. Granted, all of this is based on the model.  But it's a detailed model that so far appears   to be a very plausable explanation  for 'Oumuamua's strange behavior. Unfortunately, 'Oumuamua is gone. We'll probably  never know just what it was, but this analysis   predicts that there should be many more such  fragments of both nitrogen and water ice   passing through our Solar System. The Vera C.  Rubin Survey Telescope will be able to test   this prediction by scanning the entire night sky,   night after night. It will catch anything  moving all the way down to 27th magnitude. That should be fine enough to detect  both nitrogen and water ice fragments.   If Jackson and Desch right, then we'll soon be  studying bits of exoplanets as they float on by. Or alien hardware. Whatever. My thanks as always to my Patreon supporters  for helping to keep Launchp Pad Astronomy going.   And I'd like to welcome my newest  patrons, Tom Bock, Caley Heekin,  Craig Montgomery, and Vijayanand Sodadasi,  along with special thanks to Anna, Ricky,   and Travis for their intergalactic level  support and Michael Dowling, Steven J,   Morgan, Ann Morrison Waud for the Cosmo Logical  level, support. If you'd like to help support   Launch Pad for the price of a cup of coffee every  month, will please check out my Patreon page. And if you'd like to join me on this journey  through this incredible universe of ours,   well, please make sure you subscribe and ring  that notification bell so that you don't miss out   on any new videos. Until next time, stay home,  stay healthy, and stay curious, my friends.
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Channel: Launch Pad Astronomy
Views: 36,762
Rating: 4.7422433 out of 5
Keywords: 'Oumuamua's mystery is finally solved!, oumuamua, mystery solved, 'oumuamua explained, interstellar object, interstellar comet, what is oumuamua, interstellar visitor, interstellar object in solar system, oumuamua update, alien comet, oumuamua origin, comet borisov, avi loeb oumuamua, alan jackson, steve desch, christian ready, Launch pad astronomy
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Length: 19min 53sec (1193 seconds)
Published: Wed Mar 31 2021
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