- 3 months ago
Searching Aliens and Our Place in the Universe | How the Universe Works
Alien Galaxies, Moons, and Solar Systems! Watch as experts examine alien life amongst the stars, as well as our place in the Universe.
Dwarf Planets - 00:00 - 6:23
Hunt for Alien Life - 6:23 - 14:03
Alien Radiation - 14:03 - 20:32
Hunt for Evidence - 20:32 -28:42
Aliens of the Microcosmos - 28:42 - 35:43
Alien Worlds - 35:43 - 43:05
Alien Galaxies - 43:05 - 49:26
Alien Moons - 49:26 - 57:48
Alien Solar Systems - 57:48 - 1:11:19
Strangest Alien Worlds - 1:11:19 - 1:17:55
A Second Earth - 1:17:55 - 1:25:26
Alien Galaxies, Moons, and Solar Systems! Watch as experts examine alien life amongst the stars, as well as our place in the Universe.
Dwarf Planets - 00:00 - 6:23
Hunt for Alien Life - 6:23 - 14:03
Alien Radiation - 14:03 - 20:32
Hunt for Evidence - 20:32 -28:42
Aliens of the Microcosmos - 28:42 - 35:43
Alien Worlds - 35:43 - 43:05
Alien Galaxies - 43:05 - 49:26
Alien Moons - 49:26 - 57:48
Alien Solar Systems - 57:48 - 1:11:19
Strangest Alien Worlds - 1:11:19 - 1:17:55
A Second Earth - 1:17:55 - 1:25:26
Category
🦄
CreativityTranscript
00:00:00What would life be like on a planet in a binary system?
00:00:08Could it be better?
00:00:11Or is planet Earth really as good as it gets?
00:00:16If you're looking for an abode for life in the galaxy,
00:00:20we tend to, you know, look for a rather cozy existence out there,
00:00:23but, you know, it's possible that stars can take you on a bit of a wild ride sometimes.
00:00:30Over the past decade, we've observed mysterious objects hurtling through the galaxy.
00:00:37Scientists call them hypervelocity stars.
00:00:43When we say hypervelocity stars, we're talking some hypervelocities.
00:00:49They've been observed moving up to 620 miles per second.
00:00:53You're talking about something the size of a star, the sun, an octillion tons of mass,
00:00:58or something like that, getting flung away way faster than a rifle bullet.
00:01:05These hypervelocity stars start off in a binary system.
00:01:11But something tears them apart, something big.
00:01:16In order to create a hypervelocity star, you need a very intense source of gravitational power.
00:01:22Well, the most intense source we know of is the black hole at the center of the galaxy.
00:01:34This black hole is Sagittarius A star.
00:01:37It's supermassive, four million times the mass of our sun.
00:01:49Two stars stray a little too close, and the enormous gravity of the black hole pulls at them.
00:01:56But the star closest feels a much stronger tug, and this binary system gets ripped apart.
00:02:08It's a little bit like the Olympic hammer throw, where the hammer is one star in the binary system,
00:02:13and the Olympian is the other star.
00:02:15With the cord connecting the hammer being the gravitational tie between the binary stars.
00:02:20If you cut that cord, the other star can go flying off at very, very high speed.
00:02:27Once the cord is cut, the binary stars separate forever.
00:02:32One is trapped in the gravitational grip of the black hole.
00:02:39The other is flung out of the galaxy, becoming a literal shooting star.
00:02:45But the star may not be alone.
00:02:51If a planet is gravitationally bound to a star, and that star gets ejected from the system,
00:02:59if conditions are right, that planet can hitch a ride with that star.
00:03:05Where the star goes, the planet goes.
00:03:12If you're on a planet around a hypervelocity star, you would be the envy of poets and scientists everywhere,
00:03:18because you would have the most breathtaking view imaginable.
00:03:21You would start at the very center of the galaxy,
00:03:24and have this beautiful view of the supermassive black hole.
00:03:29Generation after generation, on this hypervelocity planet,
00:03:34would be treated to thrilling new views of the galaxy.
00:03:42By the time you're done, as you're ejected, you would see the entire Milky Way galaxy.
00:03:48Everything.
00:03:49And it would recede away from you as you moved off into space to who knows where.
00:03:55Hypervelocity planets just go to show that the universe is way stranger than fiction.
00:04:08As we learn more about stars and stellar systems, even the most fantastical imaginings of sci-fi writers,
00:04:14it doesn't even come close to what nature can produce.
00:04:21This hypervelocity star and planet go on the journey of a lifetime.
00:04:26But what about the stranded companion star stuck in the center of the galaxy next to a supermassive black hole?
00:04:33It, too, could have a planet orbiting it.
00:04:40But it's a world living on borrowed time.
00:04:46If there's a planet orbiting the star that gets left behind by the hypervelocity star,
00:04:51so the planet is now orbiting the star that's orbiting the black hole,
00:04:55that's not probably going to last very long.
00:04:58Typically, the little guy gets shot away.
00:05:01So it's entirely possible that we have hypervelocity rogue planets,
00:05:09planets without a star that are shooting out of the galaxy at high speed as well.
00:05:14But it's not a trip you'd want to take.
00:05:19Because this world is destined to wander through the emptiness of space forever alone.
00:05:32The problem with a planet is that it's no longer bound to a star,
00:05:35so the outer surface would most likely freeze.
00:05:43Binary stars create weird environments for planets.
00:05:47You could get an exhilarating view of the galaxy.
00:05:51Or you could freeze on an icy wasteland.
00:06:02But astronomers are finding bizarre new systems
00:06:06where stars are not being torn apart, but being driven together.
00:06:11Creating a cosmic event coming soon to our galaxy.
00:06:23For life to conquer the universe, first, it has to get going.
00:06:30When we look at life on Earth, it's possible that it all has a common ancestor.
00:06:34Life started at one spot, branched out, and became all the different kinds of life that we see.
00:06:39But how did it start?
00:06:42The first question to answer is, what is life made of?
00:06:47Top of the list are the most basic building blocks.
00:06:51Chemical elements.
00:06:52Here's what I know about the universe.
00:06:56The laws of physics appear to be the same everywhere.
00:07:00The chemical composition, the elements, are the same everywhere.
00:07:06And the cosmos creates these elements, not from the Big Bang, but from stars.
00:07:12Over the course of a star's life, it creates elements.
00:07:16And when a star dies, these elements are blasted out into space in a supernova,
00:07:22spreading the ingredients for life out into the cosmos.
00:07:27We, the Earth, our solar system, all the ingredients that make us us, were forged in nuclear fires.
00:07:37So the death of stars leads to the birth of life.
00:07:42Those key ingredients include oxygen, nitrogen, sulfur, and phosphorus.
00:07:50But the element most central to life as we know it, is carbon.
00:07:55All life as we know it on Earth, is based on carbon.
00:08:00Carbon forms the structure, the architecture, of our living molecules.
00:08:07Carbon is an incredibly versatile building material.
00:08:13It can bond with other elements to form long-chain molecules, each with different properties.
00:08:21As an element, it seems to be capable of producing a vast and complex chemistry.
00:08:30And that complex chemistry is what we find in life.
00:08:36We call this organic chemistry.
00:08:42But getting from basic organic molecules to complex life forms is a big leap.
00:08:48We don't really have the slightest idea, to be honest, about how life on Earth got started.
00:08:56A really big question is how you go from a mix of relatively simple organic molecules to a living system.
00:09:05We know it all starts with basic elements, created in massive quantities by the death of stars.
00:09:14But how do you start connecting those Lego bricks together to build that first cell?
00:09:20The short answer is we don't know.
00:09:23But we have some ideas of potential steps.
00:09:27Chains of organic molecules become more and more complex.
00:09:32Amino acids form proteins.
00:09:34Fatty acids form phospholipids, which make cell membranes.
00:09:39Nucleic acids form DNA, the molecule that stores genetic information.
00:09:46Eventually, a simple cell emerges.
00:09:50All of the bits you need to plug together to build a cell from scratch seems to exist in outer space.
00:09:58We found organic compounds everywhere.
00:10:02They're all over the place.
00:10:04Planets.
00:10:05Comets.
00:10:06Gas clouds.
00:10:07The very basic ingredients of life available elsewhere in our solar system.
00:10:15So there could be life everywhere.
00:10:19In 2018, NASA announces its found organic molecules on another planet.
00:10:29A planet we've always suspected of harboring alien life.
00:10:34Mars.
00:10:35So whenever NASA has a press conference and they say they have some important results to report on about Mars, everyone goes nuts.
00:10:44The internet goes mad.
00:10:47Maybe we've got photographed evidence of little green men in an UFO.
00:10:51This time, it's the Martians.
00:10:53They're going to tell us they found the Martians.
00:10:56The world listens because everyone wants to know.
00:10:59Everyone asks the question, have we found evidence of life?
00:11:02For six years, the Mars Curiosity rover has been exploring a region called Gale Crater, hunting for signs of ancient life.
00:11:16A bit like fossil hunting on Earth.
00:11:19Gale Crater is not unlike places on Earth that can preserve fossils.
00:11:23So a really good example of this would be the petrified forest in Arizona.
00:11:27This looks like a piece of wood, but in fact, it is stone.
00:11:33It is all stone.
00:11:34But it used to be a tree.
00:11:36This fossil lived 200 million years ago.
00:11:40This patch of desert in Arizona once looked completely different.
00:11:46This landscape looks very dry right now.
00:11:49But 200 million years ago, it was wet swampland with trees and flowing water.
00:11:56Like the petrified forest, Mars has also changed over time.
00:12:01Gale Crater was once a lake bed filled with fresh water.
00:12:06And it was just so exciting because we knew then that we had landed right on top of an environment that once had tons of flowing water and could very well have preserved organic materials.
00:12:19Even though it looks very barren and desolate to our eyes.
00:12:22In 2018, Curiosity drills into this ancient Martian lake and discovers organic molecules.
00:12:35Finding organics on Mars is so exciting just because, I mean, wow, those are the building blocks of life.
00:12:43Not just the elements, but actual molecules.
00:12:45There was a wave of excitement after the announcement of organics found on Mars and complex organics.
00:12:52It's not totally indicative that life is there, but it's a really good telltale sign that there may be possibly life forms on Mars.
00:13:02The results aren't proof of Martians, but the ancient lake bed is evidence that the red planet once had something else crucial for life.
00:13:14Liquid water.
00:13:19It's one thing if you have all these ingredients lying around for life.
00:13:22You could have, you know, carbon over here and hydrogen over here, maybe methane or whatever.
00:13:26You have to mix them together.
00:13:28So you need something for them to be in, a medium of some sort.
00:13:32Life needs a liquid to mix essential chemicals together.
00:13:38We're used to thinking of Earth as the only water world in our solar system.
00:13:44But new evidence says otherwise.
00:13:50As extraterrestrial visitors carrying liquid water from outer space reveal.
00:14:02In 2017, astronomers tried to solve a decades-old cosmic mystery.
00:14:11Unexplained, high-energy radiation streaming through our galaxy.
00:14:20At first, we didn't know where it was from.
00:14:25But we discovered it was gamma radiation coming from somewhere in the center of the Milky Way.
00:14:34The question is, what's making these gamma rays?
00:14:37That's hard to do.
00:14:38It's not like you can rub your hands together and generate gamma rays.
00:14:43When we took a closer look at the gamma rays, we discovered the signature of the most explosive substance in the universe.
00:14:51Anti-matter.
00:14:56Anti-matter is like normal matter, but with opposite charge.
00:15:00Opposite charge.
00:15:01That's it.
00:15:02It's matter's evil twin.
00:15:06When evil twin meets good twin, it is not a happy reunion.
00:15:14Anti-matter is scary.
00:15:15It's not like you want to have some in your kitchen.
00:15:18This stuff is very, very explosive if you want to think of it that way.
00:15:21If it touches normal matter, it releases a huge amount of energy.
00:15:26When matter and anti-matter combine, they annihilate each other and transform into high-energy radiation, just like the gamma rays seen streaming out of the center of the Milky Way.
00:15:39We see anti-matter throughout the galaxy, but strangely, the galactic center seemed to have 40% more anti-matter than anywhere else.
00:15:50Right now in the heart of our galaxy, we actually observe fountains of anti-matter that are producing 10 trillion tons of anti-matter every second.
00:16:03One of the big questions that we've wondered about for a very long time is, what's the origin of this stuff?
00:16:11Initially, there were several suspects.
00:16:14One possible source of anti-matter is the central supermassive black hole, Sagittarius A-star.
00:16:21Matter can be swirling around this and it can have such high energy that it can create anti-matter.
00:16:29But the anti-matter isn't coming from a single point.
00:16:33It's spread across thousands of light years of space.
00:16:37So Sagittarius A-star can't be the source of the gamma ray stream.
00:16:42Another suspect was dark matter.
00:16:49One of the biggest mysteries in the universe right now is dark matter.
00:16:55We know that the majority of mass in the universe is not in the same form that we are.
00:16:59It's not made of atoms.
00:17:01But whatever sort of particle it is or may be, if these things collide, they can produce anti-matter.
00:17:07And that will produce the gamma rays.
00:17:08So it's possible that as we look into the heart of the galaxy and see these extra gamma rays, that's the signal that dark matter is there.
00:17:15But the gamma ray stream we detected is too weak to have been created by dark matter.
00:17:25Then we had a breakthrough.
00:17:30We discovered that a special metal called titanium-44 could be responsible for the gamma ray stream.
00:17:39Titanium-44 is a highly radioactive element.
00:17:47That means that it wants to decay into other types of nuclei.
00:17:51When titanium-44 decays, it gives off anti-matter.
00:17:58But to produce the anti-matter seen in the galaxy's core, you would need a lot of titanium-44.
00:18:03It could be created in rare energetic events in the collision of two dead stars, white dwarves.
00:18:16A white dwarf star is a star that didn't have enough mass when it died to actually become a supernova.
00:18:23It just sort of cools off as a dead little cinder.
00:18:24But what if you have two white dwarves that are orbiting around each other?
00:18:29And as they come closer and closer and collide, all of a sudden now you have enough mass to actually kick a supernova explosion off.
00:18:41These particular kinds of supernovae are very good at producing titanium-44.
00:18:45So these kinds of supernovas are very, very good at making anti-matter.
00:18:54These supernovas erupt in the core of the galaxy once every 2,000 years.
00:19:02But outside of the core, in the disk of the galaxy where our solar system orbits,
00:19:07these supernovas happen three times as often.
00:19:15So the gamma-ray observations were wrong.
00:19:19There isn't more anti-matter in the heart of the galaxy.
00:19:23It's our region of the galaxy that contains the most anti-matter.
00:19:30The question is, are we in danger?
00:19:32If you take an ounce of matter and an ounce of anti-matter and collide them,
00:19:38you're generating a megaton of energy.
00:19:41The equivalent of a million tons of TNT exploding.
00:19:45So you don't need much anti-matter to generate a vast amount of energy.
00:19:50But the thing you have to remember is we live in this wonderful, dramatic environment of a larger universe.
00:19:57It's not dangerous. It's very far away from us.
00:20:00And it's fascinating.
00:20:03That all of this anti-matter is being produced in our galaxy.
00:20:07So just sit back and enjoy the fireworks.
00:20:12The center of the Milky Way is violent and extreme.
00:20:16But things could get a whole lot worse.
00:20:21Rogue, supermassive black holes could be lurking near our galaxy.
00:20:26And they have the power to end life as we know it.
00:20:30Earth has orbited the sun for over 4.5 billion years.
00:20:40Time enough for humankind to evolve into an intelligent and technologically advanced species.
00:20:48But compared to the age of the universe, planet Earth is just a kid.
00:20:54The Earth is over 4.5 billion years old and we think it's taken this long to create the first technological civilization, us.
00:21:04There are star systems out there much older than we are. The universe is 13.8 billion years old.
00:21:09We tend to think we're hot stuff, right? We're technologically capable. We can build rockets and we can listen to radio waves.
00:21:17But a typical other intelligent advanced civilization would be literally millions of years ahead of us in technology.
00:21:25So if an alien society has been around longer than us, how much more technologically advanced could they be?
00:21:38One method of measuring just how much is provided by the Kardashev scale.
00:21:42The Kardashev scale classifies potential alien civilizations into three types based on the amount of energy that they're able to harness from their local environment.
00:21:52A type 1 civilization can harness the energy of only its home planet.
00:21:56A type 2 could hypothetically harness the energy of its own solar system.
00:21:59And a type 3 could harness the energy potentially of an entire galaxy.
00:22:02If you're wondering where we fit on that scale, prepare for some bad news.
00:22:10We're somewhere between a 0 and a 1. We can't use all of Earth's resources. So we're at about a 0.7.
00:22:18An advanced species reaching Kardashev level 2 or even 3 could create highly advanced structures that can harness the power of a star.
00:22:29If you get to be an advanced enough civilization, eventually if your energy demands are so huge, you might build solar panels that you have enveloped your star.
00:22:40This was first thought of by Freeman Dyson and so we call these Dyson spheres.
00:22:45If such epic engineering occurs in other star systems or even other galaxies, could we pick up some evidence and then make first contact?
00:22:59The thing about a Dyson sphere is that you've completely blocked all the light coming out from a star except for the infrared because these panels are absorbing that sunlight and warming up.
00:23:12When you warm up an object, it gives off what's called thermal infrared light.
00:23:16You can scan the skies looking for that signature to see if there are any Dyson spheres out there.
00:23:212015, NASA's Wide Field Infrared Survey Explorer scanned 100,000 nearby galaxies to locate advanced Kardashev civilizations by observing infrared light leaking away from Dyson spheres.
00:23:41They detected nothing.
00:23:46No such galaxy was found, so they didn't find any infrared smoking gun.
00:23:51Given our universe is so old, surely other civilizations should have had time to evolve.
00:23:58If so, maybe we've simply missed them.
00:24:00It's entirely possible that civilizations arose, tried to communicate with the galaxy around them, and the problem was they were asking too early for us.
00:24:11They're trying to knock on our door, but our house wasn't built yet.
00:24:13Earth has been around for under one third of the universe's 13.8 billion year lifespan.
00:24:22The human race, just 300,000 years.
00:24:26A relatively tiny window of opportunity to make first contact.
00:24:32We've been looking at the sky for tens of years, something like that.
00:24:36What is the likelihood that at that exact moment someone is going to be beaming a signal toward us?
00:24:40Perhaps the universe prevents intelligent civilizations from surviving for very long, making our chances for first contact even more unlikely.
00:24:54Maybe there is something out there that is filtering us from seeing them.
00:24:59We actually call this the great filter.
00:25:01Maybe there is something that says, yeah, you're not getting past here.
00:25:04Rocky planets like ours are ideal for hosting life, but they're fragile.
00:25:11And this fragility means the universe could filter out intelligent life quickly.
00:25:22We've discovered very violent star explosions like gamma-rebursts.
00:25:27These are powerful enough, they may sterilize planets even across an entire galaxy.
00:25:31And even if intelligent species survive natural phenomenon, they may still be filtered out by hitting the self-destruct button.
00:25:44As we can tell from our own experience, the moment that we started developing technology, we also developed the means for our own destruction by changing the climate on our planet, by developing weapons of mass destruction.
00:25:59And so it's quite possible that civilizations that are advanced enough are short-lived.
00:26:05And if they are short-lived, that would explain why at this point in time there are very few of them that might be around to communicate with us.
00:26:16Finding the relics of an extinct alien civilization could be the ultimate cosmic warning for the human race.
00:26:23If we were to find a civilization out there that may have destroyed themselves by pollution or conflict, it would be almost like staring into a mirror.
00:26:33And it would be a very grim foreshadowing and maybe a lessons learned for us humans here on Earth.
00:26:38We can only hope that some advanced alien species escaped the universe's deadly filter.
00:26:49But even if E.T. still exists out there, the odds are still stacked against first contact.
00:26:56One other way that we've got this alien contact story a bit wrong is just down to the laws of physics.
00:27:10Every day, the physics of the cosmos makes our chances of contact worse because our universe is expanding.
00:27:20And it's expanding fast.
00:27:27February 2018.
00:27:30Astrophysicists at the University of Oklahoma find a potential series of rogue planets 3.8 billion light-years away.
00:27:41Ranging between the size of our Moon and Jupiter, these would be the first alien worlds ever discovered outside our galaxy.
00:27:50And maybe the first of many.
00:27:56Our galaxy alone has trillions of planets.
00:28:00The observable universe has trillions of galaxies.
00:28:03It's estimated about two trillion.
00:28:05So trillions of trillions?
00:28:07Come on.
00:28:09But finding exoplanets is no guarantee of finding alien life.
00:28:13And when it comes to contacting extraterrestrials, our efforts have met with silence.
00:28:21Our search for life has come up empty.
00:28:24Do we need to change our tactics?
00:28:26Are we doing something wrong?
00:28:27I think it's going to be very, very hard to find extraterrestrial intelligence the way that we're looking for it.
00:28:35We would have to get really, really lucky.
00:28:38But I don't think we're going to get lucky.
00:28:40I think that if we want to know whether there's life out there in the cosmos, we have to go visit it.
00:28:43We find the microcosmos in every feature of Earth.
00:28:49But where did this strange kingdom of the very small come from?
00:28:54Some of its members are so weird, they look like aliens.
00:28:58Could they have come from space?
00:29:00There's this idea that microbes could have hitched a ride on a chunk of an asteroid that would fall to Earth.
00:29:06They could form on a different planet, something hits that planet, the rock that they're sitting on gets lifted and then hits the Earth as a meteorite.
00:29:16The idea of hitchhiking bugs sounds a bit wild.
00:29:20But we have found chunks of Mars on Earth.
00:29:24Perhaps these space rocks brought life.
00:29:27It's not completely ridiculous.
00:29:30We know that rocks, for example, could come from Mars and land on Earth.
00:29:33A giant asteroid impact on Mars could blow shrapnel into space that could land on Earth.
00:29:39To learn how, we must return to the early solar system, 4.5 billion years ago.
00:29:46Many infant planets orbit a new star, our Sun.
00:29:50This infant solar system is chaotic.
00:29:54Collisions between planets are inevitable.
00:29:57The early solar system was like a pinball machine.
00:30:00Stuff was hitting, knocking stuff off, that would land somewhere, knock stuff off.
00:30:05The young Mars is in the line of fire.
00:30:08It already has primitive oceans and perhaps primitive life.
00:30:13A huge space rock smashes into the surface.
00:30:18We call the event the Borealis impact.
00:30:22It blows quadrillion tons of rock into space.
00:30:25It's not crazy to think that one of these chunks of rock traveling through our solar system has some hitchhikers on board.
00:30:35If there's some microbe riding on an asteroid that got blasted off of Mars, kind of feel sorry for it, right?
00:30:41It's just living there on Mars, doing whatever little Martian microbes do, and then a giant impact ejects this thing into space.
00:30:48In order to get from one planet to another, a cell would have to run a gauntlet.
00:30:58It's almost like winning a survival game show.
00:31:02You've got to survive being blasted off your homeworld.
00:31:05You've then got to survive the interplanetary journey inside a small lump of rock, being exposed to the vacuum of outer space, to cosmic rays, to UV radiation, being dried out and frozen.
00:31:20So the idea of moving life around the solar system or around the galaxy on asteroids poses a lot of different challenges.
00:31:28Events like the Borealis impact ejected so much rock from Mars, there were lots of opportunities for hitchhiking bugs to run the gauntlet of space.
00:31:39But could they survive the journey?
00:31:42To find out, astronauts on the International Space Station grew simple bacteria outside in space.
00:31:50After a year of being in open space, miraculously, some of these microbes survived.
00:32:00It's incredible.
00:32:01These microbes just could not be killed, even though they were in the worst possible environment for life.
00:32:08The mission, therefore, shows us that life can survive the environment and outer space.
00:32:15Life can be transferred between planets.
00:32:18Maybe life did get started on Mars and our next-door-neighbor planet and then was transferred here inside a meteorite.
00:32:28Maybe we are immigrants from Mars.
00:32:32Hitchhiking bugs may have arrived on Earth and kick-started the microcosmos.
00:32:38But now, recent studies of meteorites suggest that even if living microbes didn't make the journey, the building blocks that made them did.
00:32:49In November 2019, an international research team found an organic molecule called ribose in meteorites that had crashed on Earth.
00:32:58Ribose is a sugar.
00:32:59Ribose is a sugar.
00:33:01Ribose is a sugar.
00:33:02It's a simple sugar, but it is a sugar that is absolutely crucial to all life on Earth.
00:33:11Ribose is the sugar that makes up RNA.
00:33:15And RNA sits right in the linchpin of every cell.
00:33:20RNA is a simple form of genetic material that controls cellular function.
00:33:27It's found in most primitive creatures.
00:33:30Finding ribose on a meteorite is so important for us to understand the origins of the microcosmos because these are the building blocks.
00:33:40These are the things that it needs to get started.
00:33:43So understanding where these building blocks come from allows us to understand how the microcosmos might have evolved and started.
00:33:54The Rosetta mission found another building block for life out in space, a form of phosphorus on the comet 67P.
00:34:03This was astounding.
00:34:05Comet 67P was formed at the birth of the solar system, 4.67 billion years ago.
00:34:12And it hasn't changed since then.
00:34:14It's a time capsule from the birth of the sun and the planets.
00:34:18And it's been in the deep freeze ever since.
00:34:22So these forms of phosphorus that we found on comet 67P tell us what was available at the time the Earth was forming and then when life was getting started on primordial Earth.
00:34:35The early solar system contained many chemicals needed for life.
00:34:40It's an important discovery because it means that these compounds were around when the solar system was forming.
00:34:46So they would have been readily available for life to tap into and use to start forming cellular structure.
00:34:54These discoveries not only show that essential chemicals came to Earth, but that they exist throughout the solar system.
00:35:02We tend to think of the microcosmos as only existing on Earth in the sense that only Earth has these building blocks.
00:35:08But now these new observations suggest that the microcosmos, at least the building blocks for one, could exist beyond Earth and throughout the solar system.
00:35:18Comets and asteroids may have brought chemicals to kickstart the microcosmos.
00:35:24Now, explosive new research suggests that space rocks hitting Earth did even more.
00:35:32Could the violent impacts themselves have helped life get started?
00:35:38We've discovered some extraordinary exoplanets.
00:35:52Super hot worlds with molten iron rain.
00:35:55Super puff planets, so fragile they might blow away.
00:35:59Exoplanets that defy physics.
00:36:02But stranger still is the case of the disappearing planet.
00:36:09Over a decade ago, the Hubble telescope spotted a planet orbiting Fomalhaut, one of the brightest stars in the night sky.
00:36:20Fomalhaut is a very nearby, very young star.
00:36:23And the images of this system are incredible, because what you see is this central star surrounded by a bright ring.
00:36:29It looks just like the eye of Sauron.
00:36:32We observed the new planet, called Fomalhaut b, for six years.
00:36:38Then, something surprising happened.
00:36:42All of a sudden, it just wasn't there anymore.
00:36:45Where did this planet go?
00:36:47For it to suddenly be gone, it was amazing.
00:36:50It was astounding.
00:36:52It was terrifying.
00:36:55If Fomalhaut b can suddenly vanish, what could that mean for other planets, and us?
00:37:02We live on a planet, so we have a vested interest in understanding how planets could disappear if that's a phenomenon that exists.
00:37:11October, 2019.
00:37:14Astronomers investigate the idea of a vanishing planet by looking at BD-plus-20307, a star system straight out of the movies.
00:37:25Just like that iconic image from Star Wars, from Tatooine, where you look up and there's two stars in the sky, it's actually not that crazy.
00:37:33Out there in the wild, wild west of the universe, you have lots of different kinds of star systems.
00:37:38In fact, it's more common to have pairs of stars orbiting each other than have stars by themselves.
00:37:43If two star systems are the norm, what makes BD-plus-20307 different?
00:37:50The two stars lie within a bright disk of gas and dust, like Fomalhaut.
00:37:57But Fomalhaut is a young system, less than 500 million years old.
00:38:02BD-plus-20307 is a billion years old.
00:38:07And that's weird, because the material in the disk is so old, it should have formed new planets long ago.
00:38:15So what's going on?
00:38:17Rings of dust are a characteristic of young planetary systems.
00:38:22What does it mean when we see a disk of material surrounding an older star, a star over a billion years old?
00:38:28Well, one thing could be the collisions of planets.
00:38:34We think that in this system, planets collided, and that formed the disks that we see.
00:38:39When planets collide, they don't just spew out masses of material.
00:38:45The violence of the event shakes up the whole planetary neighborhood.
00:38:50Planetary objects come in with such energy and such speed that essentially they are vaporizing each other.
00:38:57Observing a planet essentially being destroyed tells us something about what might happen in our own solar system.
00:39:05Our planets feel very stable in their orbits, but we don't realize that in the future, those orbits might be very different than they are today.
00:39:15Early in its existence, our solar system was a demolition derby.
00:39:22With many, many collisions.
00:39:25It's how rocky planets like ours formed.
00:39:29Back then, there were more than eight or nine planets in our solar system.
00:39:34There were hundreds, and planets were running into each other and interacting with each other all the time.
00:39:39Eventually, the planets we see today formed, and our solar system settled into a nice, regular arrangement.
00:39:47Finding strange systems like BD plus 20 307 makes us question that narrative.
00:39:55One of the really valuable lessons that astronomers have learned from studying planets around other stars is that it appears very clear now that planets don't necessarily stay where they are in a solar system.
00:40:08Over time, the orbits of planets in our solar system slowly shift.
00:40:14The repercussions of these orbital fluctuations could shatter our cosmic neighborhood.
00:40:20The odds are slim, but billions of years from now, Mercury could be pulled out of its orbit by gravitational interactions with Jupiter.
00:40:30This action would set Mercury on a fateful course.
00:40:34One potential future that our solar system may have is actually that Mercury could collide with Earth, which sounds crazy, but would also be a real bummer.
00:40:47So what we see in BD plus 20 307 is theoretically possible in our own solar system.
00:40:54It's actually been a bit of a wake-up call.
00:40:58It's a transformation in our understanding of how our solar system works.
00:41:03Studying other systems shows us just how vulnerable planets can be.
00:41:08Things can change at any time in a planetary system.
00:41:13That we could be watching a planet on its orbit one day and poof, it could suffer that really big collision the next.
00:41:21But could this all explain the case of the formal halt B system?
00:41:26Could it have collided with another planet, wiping it out completely?
00:41:29Well, maybe.
00:41:34April, 2020.
00:41:37Astronomers at the University of Arizona come up with a new theory about Fomalhaut.
00:41:43Every good mystery needs a shocking twist at the end.
00:41:46And the twist in this tale could be that the planet disappeared before Hubble's eyes.
00:41:53Because it never was there to begin with.
00:41:58Instead of a planet that we thought we captured inside the ring, it was actually a collision between two smaller objects called planetismals.
00:42:08Planetesimals are infant planets.
00:42:12Bodies that measure from a few miles to hundreds of miles across.
00:42:18They smashed together and created a huge dust cloud, which we caught with Hubble.
00:42:23All we saw was a bright blob of light that looked like a planet.
00:42:27They didn't spot a planet.
00:42:29But they did learn a very important lesson.
00:42:32We're actually observing a process, part of the way that solar systems grow and are born.
00:42:37And in many ways, that's, I think, more important and more useful to us than having spotted yet another planet.
00:42:44Exoplanets are opening our eyes to the way the universe works.
00:42:49We must question some long-held assumptions.
00:42:53One standard text predicts the Sun will eventually engulf the Earth.
00:42:59But could there be a way out?
00:43:02Do some planets cheat death?
00:43:07We must say that the Sun will begin with a cloud of light.
00:43:10It's the Sun will.
00:43:15Galaxies are vast kingdoms of stars.
00:43:18Some are giant balls.
00:43:20And others, complex spirals.
00:43:23Thing is, they never stop changing.
00:43:27While it may seem, when we look out at our galaxy, that our galaxy is static and been here forever, it's not.
00:43:33Our galaxy is a dynamic place.
00:43:36It's very nature has been changing over cosmic time.
00:43:42Galaxies not only change, they move as well.
00:43:49And sometimes they run into each other.
00:43:51And when they do, it's eat or be eaten.
00:43:59There's a zoo of galaxies that you can find out there.
00:44:04And this entire zoo can interact or collide
00:44:08with any of the other members of the zoo.
00:44:12This is NGC 2207.
00:44:17It looks like an enormous double spiral galaxy.
00:44:22But it's actually two galaxies colliding.
00:44:27The collision will last millions of years,
00:44:30and eventually the two galaxies will become one.
00:44:35Collisions like this happen all over the universe.
00:44:42Our own Milky Way is no exception.
00:44:47The Milky Way is in fact a cannibal.
00:44:50And it exists in its present form
00:44:53by having cannibalized small galaxies that it literally ate up.
00:44:57And today we can see small streams of stars that are left over
00:45:01from the most recent mergers that have formed the Milky Way galaxy.
00:45:08But that's nothing compared to what's coming up.
00:45:10We are on a collision course with the galaxy Andromeda.
00:45:16And for the Milky Way, that's bad news.
00:45:21Our Milky Way galaxy is approaching Andromeda at the rate of about a quarter of a million miles per hour.
00:45:27Which means that in five to six billion years, it's all over for the Milky Way galaxy.
00:45:37You would see the entire Andromeda galaxy speeding towards us, really barreling straight into us.
00:45:47As the two galaxies interact, they both become more and more disturbed and closer and closer together.
00:45:54And the whole process starts to snowball.
00:45:58The two galaxies will enter a death dance.
00:46:01This is a simulation of the future collision, sped up millions of times.
00:46:11As the galaxies crash together, clouds of gas and dust are thrown out in all directions.
00:46:16Gravity from the merging galaxies rips stars from their orbits and shoots them deep into space.
00:46:35As we approach doomsday for the Milky Way galaxy, it would be spectacular.
00:46:40We would have a front row seat on the destruction of our own galaxy.
00:46:47Eventually, the two galaxies will go right through each other and then come back and then coalesce.
00:46:56It's strange, but the stars themselves won't collide.
00:47:01They're still too far apart.
00:47:03All of the stars are basically just going to pass right by each other.
00:47:08The probability of one individual star hitting another individual star are basically zero.
00:47:17However, the gas and dust between the stars will start to heat up.
00:47:23Eventually, it ignites and the clashing galaxies will glow white hot.
00:47:28So, at a certain point, the sky could be on fire.
00:47:39The Milky Way and Andromeda, as we know it, will cease to exist.
00:47:43And Milcomeda will be born and it will look like a whole new galaxy.
00:47:50This new galaxy, Milcomeda, will become a huge elliptical galaxy without any arms or spiral shape.
00:48:08There's no escaping what's going to happen.
00:48:15The question is, what's it mean for planet Earth?
00:48:18We may either be thrown out into outer space when the arms of the Milky Way galaxy are ripped apart,
00:48:26or we could wind up in the stomach of this new galaxy.
00:48:33Stars and planets will be pushed all over the place.
00:48:38So, this may well be the end of planet Earth.
00:48:41Galaxies all over the universe will continue to collide.
00:48:58But this age of galactic cannibalism will eventually pass.
00:49:02Because there is an even more destructive force in the universe, a force that nothing can stop.
00:49:15It will ultimately push galaxies away from each other, stretching everything until the universe rips itself apart.
00:49:26Our moon, like a lot of moons, is rocky, barren, and pockmarked with craters.
00:49:37But in one way, our moon is unique in the solar system.
00:49:41For a long time, astronomers thought the moon formed from debris left over from the birth of the Earth.
00:49:54But researchers in the 1960s came up with a radically different idea.
00:49:59They suggested it came from a giant impact.
00:50:02When we first had the idea of forming the moon from a giant impact, that was not a terribly popular idea.
00:50:25And I actually did have good science friends, colleagues coming to me saying, you know, we really have to exhaust all the slow evolutionary theories before we start talking about cataclysms.
00:50:38The evidence Bill Hartman needed was on the moon itself.
00:50:46And the proof had to wait until Apollo astronauts finally went there in 1969.
00:50:55They brought back hundreds of pounds of moon rocks.
00:51:01Scientists analyzed the rocks and were amazed.
00:51:05They were identical to rocks in the Earth's crust.
00:51:09And they'd been superheated.
00:51:13So how did pieces of the Earth's crust become super hot and wind up on the moon?
00:51:19Hartman was pretty sure he knew.
00:51:21This whole idea was that the Earth forms, now you hit it with something, you blow all this light, rocky material off the top, that material goes into orbit and makes the moon.
00:51:32The moon's just made out of rocky debris.
00:51:39Imagine our chaotic solar system four and a half billion years ago.
00:51:43The young Earth is just one of a hundred or so new planets orbiting the Sun.
00:51:56One of them is a Mars-sized planet called Thea, and it's on a collision course with Earth.
00:52:07They smash into each other at many thousands of miles an hour.
00:52:18Thea is destroyed, and Earth barely survives.
00:52:21The impact blasts billions of tons of debris into space.
00:52:37The Earth's gravity pulls it into orbit around the planet.
00:52:40Now, these hunks of leftover Earth clump together and form our moon.
00:52:50That's the theory, anyway.
00:53:09But how do you test it for real?
00:53:10Here at NASA's Vertical Gun Range, they're recreating that ancient collision in a lab.
00:53:21This 30-foot-long gun fires a tiny projectile at 18,000 miles an hour.
00:53:30The projectile is Thea.
00:53:33This ball represents the Earth.
00:53:35By changing the angle of Thea's impact, the team can figure out how precise the ancient collision had to be in order to make the moon.
00:53:45In the first shot, Thea hits the top of the Earth with a glancing blow.
00:53:51So here's the Earth, if you will, suspended in space, and now it's gotten hit.
00:53:55So now we see the planet, the ejecta, is being ripped out of the Earth and is forming this giant impact basin.
00:54:06And if this really were the Earth, this basin would be thousands of kilometers, thousands of miles across.
00:54:14In this simulation, Thea only skims off the surface of the planet, and very little debris is thrown out into space.
00:54:22Not nearly enough to build our moon.
00:54:33The second shot is a head-on collision.
00:54:40Kapow! That's the end of planet Earth. It's gone.
00:54:43Some of the debris is going to go out of the solar system. Some of the debris will re-accrete to form small planetesimals within the solar system.
00:54:52There's no Earth left, so there's no gravity to gather the debris and form the moon.
00:55:09Now, the gun is set to just the right angle, halfway between a glancing blow and a direct hit.
00:55:16So we'll see what happens if the Earth barely survives.
00:55:28Oh, oh, gorgeous! Oh my gosh! Kapow!
00:55:33Now we have the entire part of the Earth being ripped apart.
00:55:37But the vapor plume is, oh my gosh!
00:55:39Ha, jeez! That is gorgeous!
00:55:51But this was the beginning. The beginning of our moon.
00:55:58The experiment shows that Thea could have smashed into the Earth and formed the moon.
00:56:03But the collision had to be just right.
00:56:09And lucky for us, it was.
00:56:18Today, the moon orbits 250,000 miles from Earth.
00:56:23But when it first formed, the moon orbited just 15,000 miles above the Earth's surface.
00:56:30500 million years after the moon formed, if we looked up in the sky, the moon would have comprised a tremendous portion of the sky.
00:56:43It would have been enormous, because the moon would have been much closer.
00:56:48Back then, the Earth was rotating so fast, a day lasted just six hours.
00:56:53But the moon was so close, its gravity acted like a break.
00:57:05It slowed our planet down, until a day now lasts 24 hours.
00:57:10The moon's gravity also created giant tides that surged across the planet, churning up the seas, mixing minerals and nutrients.
00:57:23This created the primordial soup from which the first forms of life arose.
00:57:29Without our moon, life on Earth may never have happened.
00:57:32And there may be other moons with a link to life as well.
00:57:41Moons may be the great biology experiments of the universe.
00:57:46The true laboratories of life itself.
00:57:49The planets of the solar system grew from a giant disk of dust and gas.
00:58:03The four inner rocky planets close to the sun, and the giant gas planets further out.
00:58:12But Uranus and Neptune seem out of place.
00:58:19There wasn't enough material this far from the sun to make such big planets.
00:58:24So why are they out here?
00:58:29That led us to a theory where Uranus and Neptune formed very close to the sun, and were actually violently pushed outward.
00:58:40But what could move two massive planets clear across the solar system?
00:58:44We believe that Jupiter and Saturn got into this funny configuration, where Jupiter went around the sun exactly twice, every time Saturn went around once.
00:58:57And that configuration allows the planets to kick each other more as they pass one another.
00:59:03And that caused the whole system to go nuts.
00:59:05The combined gravity of Jupiter and Saturn pulled hard on Uranus and Neptune, and dragged them away from the sun.
00:59:16As they moved outward, the two planets crashed through asteroids and other debris left over from the formation of the other planets.
00:59:23This sent billions of chunks of rock flying in all directions.
00:59:45Some rocks formed the asteroid belt, but most were thrown out to create the vast Kuiper belt.
00:59:59The analogy I like to use is, think of a bowling match, and the bowling balls go down and the pins just go kaplooey.
01:00:12That's what happened in the outer part of the solar system.
01:00:14But the gravitational push from Jupiter and Saturn was so strong, it may have reversed the position of the two planets.
01:00:24It looks like it's possible that Uranus and Neptune actually formed in the opposite order.
01:00:30Neptune was closer to the sun than Uranus, but these gravitational interactions actually swapped their positions.
01:00:36The blizzard of rocks that Uranus and Neptune ran into acted like a brake, and slowed them into the orbits they keep today.
01:00:53While Uranus and Neptune stabilized in their new orbits, a swarm of comets and asteroids rained down on the inner planets,
01:01:00bringing with them a precious cargo.
01:01:13The asteroids carried water from the solar system's outer reaches.
01:01:19Without the movement of Uranus and Neptune, and the shower of asteroids, water might never have reached Earth.
01:01:26Then there would have been no oceans, and no life.
01:01:33Evidence of this bombardment can still be seen today.
01:01:37But not on Earth.
01:01:40When astronauts examined craters on the Moon, they found that most formed at the same time.
01:01:463.9 billion years ago.
01:01:49The time of the great bombardment.
01:01:51The idea of planets changing orbits may sound far-fetched.
01:01:59But scientists have seen it happen in other solar systems.
01:02:03And they now think it's just the way all solar systems work.
01:02:07When we look out into the galaxy, and look at planets around other stars,
01:02:13we see lots of evidence of those kind of events happening elsewhere.
01:02:17In one far-off system, scientists have seen something quite extraordinary.
01:02:25A planet as big as Jupiter.
01:02:28But it's not acting like the Jupiter we know.
01:02:31Some of these giant planets are found orbiting very close to their host star,
01:02:35taking only days, a few days, to go around the host star.
01:02:46Obviously, such close-in Jupiters are blow-torched by the star,
01:02:51raising the temperature of the planet up to 1,000 or 2,000 degrees Celsius.
01:02:55A gas giant could not have formed this close to the Sun.
01:03:02It's way too hot.
01:03:04The only explanation is that it must have formed out there,
01:03:08and then moved in here.
01:03:09An identical thing could have happened in our own solar system.
01:03:23Scientists have found large amounts of the element lithium on the surface of the Sun.
01:03:27Lithium doesn't normally exist in stars, but it is found in gas planets.
01:03:42Perhaps there was another gas giant in our own solar system that crashed into the Sun.
01:03:47This would explain how the lithium got there.
01:03:49Ours is not the only solar system in the Milky Way galaxy,
01:04:08and most of the others seem strange in comparison.
01:04:12As we've seen, some planets follow unusual orbits,
01:04:16while some smash into each other.
01:04:27Others dive into their stars.
01:04:34So, why are the orbits of our own planets so regular and stable?
01:04:39Well, that's because all the planets have motion left over from the formation of the solar system.
01:04:44When the nebula collapsed around the Sun as the Sun was forming,
01:04:49there was an intrinsic motion, and that gave our planet a velocity.
01:04:54Literally, we are falling freely toward the Sun at all times,
01:04:59but we're going so fast we keep missing it.
01:05:01That's what an orbit is.
01:05:02It's similar to a merry-go-round.
01:05:09The faster it spins, the further and further you're thrown from the center.
01:05:16And when it slows down, you lose momentum and fall back inwards.
01:05:20It's similar to this with planets.
01:05:25The disk that gave birth to the planets was spinning,
01:05:29and the momentum left over from that keeps everything going around to this day.
01:05:36Moving at 107,000 kilometers an hour, the Earth takes one year to orbit the Sun.
01:05:41Planets further from the Sun have bigger orbits, move slower, and take longer.
01:05:51Saturn orbits the Sun once every 29 years.
01:05:55Neptune takes 164 years.
01:05:59Each planet stays on a precise path around the Sun, which is good for us.
01:06:04Our solar system has a somewhat fortunate spacing of the planets with nearly circular orbits,
01:06:18which keeps the whole house of cards from falling apart, crumbling, scattering to the wind.
01:06:24If our solar system did not have nice, neat, stable, nearly circular orbits,
01:06:36the Earth wouldn't be here, and we wouldn't be here talking about it.
01:06:45The planets are on safe, stable orbits.
01:06:48But billions of comets and asteroids are not.
01:06:59Many come streaking into the inner solar system,
01:07:03and when they do, Earth's in jeopardy.
01:07:06The meteor crater which we see here today formed as a result of a 150-foot rocky iron object
01:07:23coming in and slamming into the Earth roughly 50,000 years ago.
01:07:29Some of the objects on a collision course can be much bigger.
01:07:33Look at the Moon.
01:07:35It's covered with large impact craters.
01:07:38Earth has been hit too, a lot.
01:07:47But these craters have eroded.
01:07:53We know that a huge asteroid smashed into the Earth off the coast of Mexico 65 million years ago.
01:08:00It was travelling at 72,000 kilometers an hour, and when it hit,
01:08:05it released more energy than 5 billion atomic bombs.
01:08:08Are through the sky the Radios.
01:08:11And where?
01:08:18Where?
01:08:20responding to the urban latey roof!
01:08:22But there's too much closer.
01:08:24I can see how rich could he have the熱 Bandit finally!
01:08:25What does he have learned?
01:08:27They are half-happed.
01:08:29He is Wer Moore!
01:08:31The only thing is the perfect time.
01:08:33He isaurabide.
01:08:34This appears in size as a river.
01:08:35Of course, he knows.
01:08:36It wiped out 70% of life on Earth.
01:08:52A few more impacts similar to that could destroy all life on Earth.
01:08:57But, believe it or not, Earth has a giant protector.
01:09:01Jupiter is more than just another pretty face through the telescope.
01:09:07It's actually really important for life on Earth.
01:09:10Jupiter's gravity is so huge, and it's just in the right place in the solar system,
01:09:14that it protects the Earth from comets that come from deep in the solar system
01:09:18and swing by the sun and could possibly hit the Earth.
01:09:24Jupiter plays the role of the biggest baseball bat in the solar system.
01:09:27As these comets come by, most of them get knocked out of the solar system by Jupiter.
01:09:37In 1994, comet Shoemaker-Levy 9 raced towards the inner solar system.
01:09:43But it never got past Jupiter.
01:09:45Astronomers watched as Jupiter tore it to pieces
01:09:55and dragged its remains down to the planet's surface.
01:10:00We have seen comets smash into Jupiter,
01:10:03creating fireballs that were bigger than the Earth.
01:10:10They were the biggest explosions ever seen in our solar system.
01:10:15Had that comet hit us, it would have resurfaced the planet.
01:10:23It would have been the end of life as we know it.
01:10:25If Jupiter wasn't there, we believe that the impact rate on the Earth
01:10:28would be something like a thousand times more than we see today.
01:10:32We're extremely fortunate, as Earth has the perfect orbit.
01:10:45Jupiter protects us from asteroids and comets.
01:10:51We're close enough to the sun for liquid water,
01:10:54but not too close that it boils away.
01:10:57It's just the right combination for life.
01:10:59The question is,
01:11:05if our solar system could create the perfect conditions,
01:11:08could it occur in other solar systems too?
01:11:12Planet hunters have spotted a solar system 20 light years away,
01:11:16and there is a planet just the right size
01:11:19and in just the right place.
01:11:22Take a look at the night sky.
01:11:32We now know that planets probably surround
01:11:35almost every point of light you see.
01:11:41But there's more.
01:11:43For every star we can see,
01:11:45there are countless others too dim for our eyes to pick out.
01:11:49These are the red dwarfs,
01:11:54far smaller than the sun,
01:11:56but home to planets by the truckload.
01:11:59And many of these worlds are made from rock,
01:12:02like the Earth.
01:12:05There are more red dwarfs than any other kind of star in the galaxy,
01:12:09and these stars have planets too.
01:12:11So the most common type of planet in our galaxy
01:12:13is one that lives around a red dwarf.
01:12:15Of the billions of red dwarfs in the Milky Way,
01:12:22more than 1 in 20 have planets
01:12:24that orbit at just the right distance
01:12:26for liquid water to collect on the surface.
01:12:32Any closer,
01:12:33the temperature would be too hot
01:12:35and the surface water would boil.
01:12:39Any farther away,
01:12:40and the water would freeze.
01:12:44It's often called the Goldilocks Zone
01:12:47because it's just right for oceans to form,
01:12:51just as they did on the Earth.
01:12:53Could one of these warm, wet worlds
01:12:56provide a habitat for life like us?
01:13:01That's kind of the holy grail of this whole thing,
01:13:03to find something that looks like home.
01:13:06For one thing,
01:13:07that means that it could have life on it.
01:13:10It could be habitable.
01:13:11And that's something
01:13:12that we've always wanted to know the answer to.
01:13:14Are we alone?
01:13:18These rocky, wet planets
01:13:20may seem like dead ringers for the Earth,
01:13:24but there's a catch.
01:13:28Many red dwarf worlds
01:13:30orbit so closely to their dimmost stars
01:13:32that the same side of the planet
01:13:35would always face inwards,
01:13:38held in place forever
01:13:40by the star's immense gravity.
01:13:43Scientists called this phenomenon
01:13:45tidal locking.
01:13:49We're all familiar with the fact
01:13:50that the Earth spins on its axis
01:13:51and gives us night and day.
01:13:53But if you move in closer to a star,
01:13:56eventually the gravitational interaction
01:13:57will stop that rotation.
01:13:59One side of the planet
01:14:03will always face the star,
01:14:04one side will always face away,
01:14:06and you're tidally locked.
01:14:10If you land on this planet
01:14:11and look around,
01:14:12you're going to see stuff
01:14:13that's very different
01:14:14depending on where you are.
01:14:17If you're on the point on the planet
01:14:20that is underneath the star
01:14:21so that when you look up,
01:14:22that star is straight up,
01:14:24that's where it's always going to be.
01:14:25It never rises,
01:14:26it never sets,
01:14:27it never moves.
01:14:29That's where the star is.
01:14:33Now if you're on the other side of the planet,
01:14:35it's always nighttime.
01:14:36You look up,
01:14:37you never see your host star
01:14:39in the sky.
01:14:42In 2016,
01:14:45astronomers discovered
01:14:46a potentially Earth-like planet
01:14:48orbiting the Sun's
01:14:49closest neighboring star,
01:14:52Proxima Centauri.
01:14:53The planet,
01:14:56dubbed Proxima b,
01:14:58sits close enough to its host
01:15:00to have oceans like the Earth,
01:15:03but scientists suspect
01:15:04it's tidally locked.
01:15:07The result,
01:15:08Proxima b may be staring
01:15:10at its parent star
01:15:11like a giant eyeball.
01:15:14The night side
01:15:15is a dark, frozen wilderness.
01:15:18The day side,
01:15:19a sun-blasted desert.
01:15:21But between the two
01:15:23lies hope for life.
01:15:26A long, thin strip of land
01:15:27in permanent dusk
01:15:29wraps around the planet
01:15:31like a ribbon.
01:15:32J.D. Radebaugh pictures
01:15:38an eerie twilight zone
01:15:41where dark glaciers melt
01:15:43to fill vast lagoons,
01:15:46just as Earth's glaciers
01:15:47do during the summer.
01:15:49The boundary
01:15:51between these two
01:15:52completely different landscapes
01:15:54is something like
01:15:55what we're sitting on right now.
01:15:57Basically, we would have
01:15:58liquid water
01:16:00flowing off of these glaciers,
01:16:01pouring off the glaciers,
01:16:02and heading out
01:16:03into the wasteland.
01:16:06And icebergs calving off
01:16:08into this beautiful bay.
01:16:11We've got liquid water,
01:16:13we've got energy
01:16:14from this burning sun,
01:16:15and so this is exactly
01:16:16the kind of place
01:16:16where we would look for life.
01:16:19A ring of hope for life
01:16:21on a planet orbiting
01:16:23the sun's nearest neighbor.
01:16:26Could Proxima B
01:16:27really be home
01:16:28to alien civilizations?
01:16:31Until we go there,
01:16:33the jury's out.
01:16:37But red dwarfs burn
01:16:39for trillions of years,
01:16:40and they outnumber
01:16:41the other stars in the sky
01:16:43three to one.
01:16:45If advanced alien civilizations
01:16:48really are out there,
01:16:50the planets of red dwarf stars
01:16:52could be ideal places
01:16:54to find them.
01:16:56Let's say that we were sitting
01:16:57on a planet around
01:16:59one of these red dwarfs
01:17:00maybe a trillion years from now.
01:17:02We could still be sitting here.
01:17:03We've never seen a red dwarf die.
01:17:06And so if that's true,
01:17:07then there's plenty of time
01:17:08for life to have gotten started.
01:17:09So not only do we have
01:17:10microbial life,
01:17:12but maybe even more complex life,
01:17:14and then take it a step further,
01:17:15we might even have
01:17:16intelligent life
01:17:17in these locations.
01:17:21It's amazing
01:17:22that even tiny stars
01:17:24can have potentially
01:17:25habitable rocky planets,
01:17:27no matter how weird
01:17:29these worlds may turn out to be.
01:17:31But when astronomers
01:17:35turn their telescopes
01:17:37to bigger stars,
01:17:39the surprises keep coming.
01:17:42These sun-sized stars
01:17:44have planets too,
01:17:45and some of them
01:17:46could be the weirdest yet.
01:17:50Imagine a gas planet
01:17:52so black
01:17:53it appears to be eating light.
01:17:56If an alien astronomer
01:18:08were to file a report
01:18:09on our home solar system,
01:18:11they might make
01:18:12a surprising observation.
01:18:13Because of all the eight planets
01:18:15that orbit the sun,
01:18:16they could easily conclude
01:18:18that two, not one,
01:18:20were suitable for life.
01:18:24It's an easy mistake to make,
01:18:25because the sun has two planets
01:18:27within its Goldilocks zone,
01:18:29the Earth
01:18:30and Mars.
01:18:33Both planets have surfaces
01:18:35warm enough
01:18:35for liquid water to pool on.
01:18:38But while the Earth
01:18:39is blessed with warm,
01:18:40liquid oceans,
01:18:42Mars is dry and dead.
01:18:45The one crucial difference
01:18:47between these two planets
01:18:48could be the key
01:18:50to finding truly
01:18:51habitable exoplanets,
01:18:54a magnetic shield
01:18:55Our sun is constantly
01:19:02hurling deadly radiation
01:19:04out towards us.
01:19:07Only our magnetic shield,
01:19:09the magnetosphere,
01:19:10saves us.
01:19:13Without it,
01:19:14the solar wind
01:19:15would blow our atmosphere away.
01:19:17And without an atmosphere,
01:19:18liquid water
01:19:19could not exist
01:19:20on the surface.
01:19:21In order to have liquid water,
01:19:25not only do you need
01:19:26the right temperature,
01:19:27but you need
01:19:27the right pressure.
01:19:28You know,
01:19:28if there were no atmosphere
01:19:29here right now,
01:19:30even at the same temperature
01:19:32we are today,
01:19:33all of the water
01:19:34would boil off
01:19:34into vapor immediately.
01:19:37So where does the Earth's
01:19:38magnetosphere come from?
01:19:40And why doesn't Mars have one?
01:19:42Actually, in the past,
01:19:46both Earth and Mars
01:19:48had magnetospheres,
01:19:49but Mars lost its
01:19:50around 4 billion years ago,
01:19:52and with it,
01:19:54the potential for life.
01:19:55Both the Earth and Mars
01:20:03were born into a realm
01:20:05of violence.
01:20:07Asteroids smashed
01:20:08into their surfaces,
01:20:10turning rock and metal
01:20:11into a molten mass.
01:20:15As they started to cool,
01:20:16a solid crust formed
01:20:18on the surface,
01:20:19but the molten metal below
01:20:21churned as the planets turned,
01:20:23inducing a magnetic field
01:20:25which rose high up
01:20:27above the surface
01:20:28of both planets.
01:20:30At the same time,
01:20:32active volcanoes
01:20:32pumped gas
01:20:34into the space
01:20:35around each planet.
01:20:36Protected by the newly
01:20:38formed magnetic field,
01:20:39these gases built up
01:20:41into thick atmospheres,
01:20:43creating the air pressure
01:20:44for liquid water
01:20:46to run on the surface.
01:20:48For over 100 million years,
01:20:50both Mars and Earth
01:20:51were warm,
01:20:52wet paradises
01:20:54primed for life
01:20:55to take off.
01:20:56Then, quite suddenly,
01:20:59Mars' magnetic protection
01:21:00disappeared.
01:21:02The solar wind
01:21:03blew its atmosphere
01:21:04into space,
01:21:06and its oceans
01:21:07boiled away,
01:21:08leaving the dry,
01:21:10sterile red rock
01:21:11we see today.
01:21:14Mars' fundamental problem
01:21:16is that it's smaller
01:21:17than Earth.
01:21:17and because it's smaller,
01:21:19the internal core
01:21:21of Mars cooled down
01:21:22and solidified.
01:21:25And once it becomes
01:21:25a solid metal,
01:21:27there's no more
01:21:28magnetic field.
01:21:29The magnetic field
01:21:29shuts off, essentially,
01:21:31and the atmosphere,
01:21:33therefore,
01:21:33is vulnerable
01:21:34to both energy
01:21:35and radiation
01:21:36from the sun
01:21:37and the rest
01:21:38of the galaxy
01:21:39and probably
01:21:40just blew off.
01:21:42Whatever life
01:21:43was on there,
01:21:44at least on the surface,
01:21:45is now completely exposed.
01:21:49All rocky planets
01:21:50will one day
01:21:50lose their magnetospheres
01:21:52as their cores
01:21:53cool and turn solid.
01:21:56So, to know
01:21:57if an exoplanet
01:21:58is alive,
01:21:59you need to work out
01:22:01if its magnetosphere
01:22:02is still active.
01:22:04But magnetospheres
01:22:05are tough to measure
01:22:06because they are
01:22:08unbelievably weak.
01:22:10The Earth has
01:22:11a magnetic field
01:22:12of approximately
01:22:13half a gauss,
01:22:15which,
01:22:15when you think about it,
01:22:16is actually really weak.
01:22:18Our fridge magnets
01:22:19are about 100 gauss,
01:22:20so they're much stronger.
01:22:24Exoplanets
01:22:25are too far away
01:22:26for us to measure
01:22:27such weak magnetic fields
01:22:28directly.
01:22:30But,
01:22:31there is
01:22:31an indirect method.
01:22:34When electrons
01:22:36in the solar wind
01:22:37interact with
01:22:38the planet's
01:22:39magnetosphere,
01:22:40they emit radio waves
01:22:41that beam out
01:22:42into space,
01:22:44turning the planet
01:22:45into a giant
01:22:46radio beacon.
01:22:50Astronomers like
01:22:51Evgenia
01:22:52hope to use
01:22:53these signals
01:22:54to spot
01:22:54habitable exoplanets.
01:22:57Not only that,
01:22:58the frequency
01:22:59of the signal
01:22:59should also tell her
01:23:01how big the planet is.
01:23:03if we're looking for
01:23:08the magnetic signature
01:23:09in the radio waves
01:23:10of a giant planet,
01:23:12say a hot Jupiter,
01:23:13we expect it to have
01:23:14a strong magnetic field
01:23:16and therefore it would
01:23:17have a high frequency,
01:23:19around 100 megahertz,
01:23:21kind of where
01:23:21the limit of this radio is.
01:23:23However,
01:23:24a weaker field
01:23:25like Earth's
01:23:26requires us to go down
01:23:27to lower and lower frequencies.
01:23:29So instead of 100 megahertz,
01:23:31we go down to 10 megahertz.
01:23:36But hunting for exoplanets
01:23:38at 10 megahertz
01:23:39presents a unique challenge.
01:23:44Because the Earth's
01:23:45own magnetosphere
01:23:46creates a deafening
01:23:48radio roar
01:23:50at that frequency.
01:23:50So to find alien Earths
01:23:55using radio
01:23:56requires a dish
01:23:57in space.
01:23:59When we want
01:24:00to look for
01:24:01magnetospheres
01:24:02of extrasolar planets,
01:24:04we really need
01:24:05to get outside
01:24:06of the Earth-Moon system
01:24:08in order to get away
01:24:09from all the radio frequencies
01:24:11that are bouncing
01:24:11around the Earth.
01:24:12with a slew
01:24:17of new technologies
01:24:18and upcoming technologies,
01:24:20scientists are edging
01:24:22ever closer
01:24:22to the ultimate prize,
01:24:24finding a second Earth.
01:24:27I wouldn't be surprised
01:24:29if we have that data
01:24:30about an Earth
01:24:31and about life on it
01:24:32around another star
01:24:33in 10 or 15 years.
01:24:35I'm hoping to see that soon.
01:24:39Using shadows,
01:24:41rainbows,
01:24:42and now radio,
01:24:44we finally have the tools
01:24:45to detect a planet
01:24:47just like our own.
01:24:50But,
01:24:51in the rush
01:24:52to find the Earth's
01:24:53identical twin,
01:24:54are we missing
01:24:55something big?
01:24:59What if Earth
01:25:00is an outlier,
01:25:02a freakishly
01:25:03lucky place
01:25:04on the very fringes
01:25:06of habitability?
01:25:08Could there be
01:25:08another kind of planet
01:25:10out there,
01:25:10even better for life?
01:25:12Even better for life?
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