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One day future humans must leave earth for a new home among the stars finding another habitable world is not just a science fiction dream it has to do with the survival of humanity today astronomers are laying the groundwork for our move to a new earth but the more alien worlds they discover the more they learn how deadly the cosmos really is the universe has this one rule when it comes to life kill it all to pinpoint our new home astronomers must unlock why space is so savage what unleashed one of the most powerful blasts of energy ever seen to fry a promising alien world you would be dead so fast you wouldn’t even know it how did our cruel sun destroy earth’s sister planet it just didn’t make it and became this inhospitable hellscape we dive through waves of deadly radiation and plunge into suffocating atmospheres to reveal the raw destructive power of the cosmos humanity’s days on earth are numbered the sun’s brightness will increase by 10 percent over the next 1 billion years this extra heat will boil away earth’s oceans and incinerate all life on our planet.

Our fate is written in the stars we must leave and find a new home in another part of the galaxy to ancient people the earth seemed absolutely eternal it must have always been here and it always will be here we know planets change they live and then they die our galaxy stretches 100 thousand light years across where and this huge expanse is somewhere that can support complex life planets are formed from the leftover debris from star formation we have over 400 billion stars in ourgalaxy that means we can have trillions of planets astronomers call these alien worlds exoplanets in 2016 exoplanet hunters make an exciting discovery they find a rocky planet that is roughly the same size as earth the planet orbits proxima centauri the closest star to our sun they name the planet proxima b it is just 4. 2 light years from earth and it is in just the right spot to potentially support complex life like humans finding proxima b was a game changer because not only is it a planet in the habitable zone of its star it’s the closest star to us so this means that we could potentially go there this changes the future directions of science on earth the habitable zone is the sweet spot around a star where temperatures are right for liquid water to exist on the surface of a planet if you’re too close to the star that water’s going to boil away
if you’re too far it’s going to freeze and if you’re in that zone you can have liquid water on your surface the signs look good that proxima b might have what it takes to be a home for humans in the future but what astronomers see next puts the celebrations on hold 2018 violent waves of radiation slam into proxima b the blast wipes out hopes that the planet can support life this is one of the biggest high energy events involving an exoplanet that we’ve ever been able to witness what could have caused such a huge release of energy astronomers attempt to unlock the mystery they examined the prime suspect the star that proxima b orbits proxima centauri astronomers measure the light output from thousands of stars in our galaxy a sudden increase in starlight is evidence that the star is releasing a stellar flare a stellar flare is an explosion of intense radiation that erupts from a star’s outer layers proxima centauri is a red dwarf star astronomers discover that this type of star emits around 80 000 times more flares than a star like our sun observations also reveal that each flare is around a thousand times more powerful than the average type of flare that our sun emits small red stars have gigantic flares they’re so huge they actually double the brightness of the star that means the flare is as bright as the star is so imagine if the sun did that imagine if the sun doubled its brightness right now that wouldn’t be good the evidence is clear a super powerful flare from proxima centauri fried proxima b splitting open the star reveals why it is so volatile proxima centauri is so small that its core touches the churning layer of hydrogen that surrounds it the extreme heat in the core drive streams of superheated plasma to the surface like a furiously boiling pot of water huge eruptions of plasma spew from the star with the force of a billion hydrogen bombs the flares fan out through space they slam into proxima b and extinguish any chance that the planet can support life proxima centauri discharges mega flares like this three times a year these extreme flares will wipe out the ozone layer of every planet in the habitable zone of the star the earth has a layer of protective ozone in its atmosphere that absorbs ultraviolet light from the sun which is great because that kind of light is harmful to life on earth the problem with proxima centauri is that it is a flare star and if proxima centauri b has an ozone layer it’ll get destroyed by this constant barrage of high energy radiation the destruction of this layer ruins any chance that humans could one day live on proxima b the kind of light that these flares emit is the kind of light that we use to sterilize surfaces a dna molecule would just be completely destroyed a new earth must orbit a stable star to support complex life the hunt for our next home continues can three newly discovered planets in the same system sustain humans on a thin boundary between fire and ice and can a jupiter-sized alien planet unlock the mystery of why habitable worlds are so hard to find [Music] humans must leave earth before our sun incinerates our world and forge a future on a planet and another part of the galaxy today astronomers lay the groundwork for our eventual move to a new planet in 2017 they discover an extraordinary system 40 light years away from earth a dwarf star called trappist-1 sits at the center of the system around it orbits seven rocky planets and all of them are a similar size to earth the planets are so close to trappist-1 that a year on these worlds lasts between 2 and 19 earth days three of the planets fall inside the habitable zone of the system could one of these worlds be our future home there are times as a scientist where you discover something out there that honestly if it wasn’t right in front of our eyes i would not believe that it exists and the trappist-1 system absolutely blows me away telescopes analyze the system in more detail they reveal it is likely that these planets have unusual orbits they do not spin around their star in the same way as earth revolves around the sun instead many astronomers think that the same sides of all seven planets face their star they call this tidal locking you can witness an example of tidal locking an action really close to the earth just look up in the night sky and look at the moon you only ever see one side of it one face is always pointed toward the earth this is because the moon is tidally locked to the earth and what that means is that the time it takes for the moon to spin once on its own rotational axis is exactly equal to the time that it takes to orbit the earth once the close proximity of these planets to their star unlocks why this happens in the trappist-1 system

the star trappist-1 is 20 000 times more massive than its orbiting planets and its immense gravity grips them as they huddle in close the star’s gravity warps each planet out a huge bulge of rock on the side facing the star the star tugs on the bulge like a handle gently slowing the rotation of the planet after millions of years the planet slows down so much that one side remains locked always facing the star living on a tidally locked world in the trappist-1 system poses a big challenge for future humans the rotation of earth ensures that no part of the planet gets too hot or too cold to support life it’s the spin of our home planet that allows it to actually harbor life it’s this spin that evenly distributes thermal energy across our planet’s surface and creates conditions hospitable for life itself but tidal locking turns the trappist-1 planets into super extreme worlds of two halves it’s likely that every planet in the trappist-1 system is tidally locked eternal darkness shrouds one face the other is bathed forever in starlight the star’s powerful radiation roasts the surface of the dayside and water evaporates away the night side experiences an endless cosmic winter water freezes solid as temperatures plummet in between these two hellish half worlds is a thin strip where it is always dawn temperatures here could be just right to support complex life any brave humans who do settle this thin strip will find themselves living on a knife edge huge mega storms will engulf the areas where the scorching winds from one half of the planet meet the frozen gases of the other  people here will live in a never-ending super hurricane these mega storms raging inside this potentially habitable band make a trappist-1 planet too volatile for humans to live on long-term i don’t want to say that life can’t exist on a tidally locked planet but if our species were to have its pick of a next planet to move to we probably wouldn’t pick a tidally locked planet as our new home human space travelers in the future must search elsewhere for a place to live but the odds of finding it are stacked against them just two percent of the over four thousand exoplanets found so far are in the sweet spot of their star’s habitable zones why are rocky planets within habitable zones so hard to find astronomers believe that a clue may lie and where they find another type of exoplanet telescope observations show that many exoplanets are gas giants made from hydrogen like our jupiter when you look at our own solar system there’s one planet that absolutely dominates and that’s jupiter jupiter is actually large enough that you could fit a thousand earths inside it and if you added up all of the mass of the planets jupiter would be about 70 of that so when you think about what’s really going on in a solar system these giant planets are the story you need to tell [Music] the jupiter in our solar system is almost 480 million miles from the sun but most jupiter-like exoplanets discovered so far orbit less than 10 million miles from their stars the super close proximity to their stars heats up the surface of these gas giants to over 7 700 degrees fahrenheit why are these hot jupiters so near to their stars and does this closeness point to why future space travelers could find it hard to discover habitable rocky planets one day humans must leave earth to find a new home among the stars astronomers today find few rocky planets with the potential to support human life in the future what they do find are many gas giant worlds that orbit close to their stars do they unlock the mystery of why astronomers find so few earth-like planets a clue comes from special telescopes that unlock what gas giant exoplanets are made of even though most exoplanets can’t be seen directly we can figure out what’s in their atmosphere because as they orbit the star and pass directly in front of it from our point of view that starlight passes through their atmosphere different constituents in that atmosphere absorb specific colors of light so by examining the colors of light we can figure out what’s in its atmosphere the telescopes discover something strange about the atmosphere of a hot jupiter called wasp 39b the data reveals that this planet contains water how can a planet that’s hotter than the surface of many stars contain a liquid that should vaporize and extreme heat finding a planet with a lot of water in its atmosphere close to a star there’s no way that planet formed there astronomers think the answer lies in the way that many gas giant planets evolved systems start life as flat discs of gas and rock a star ignites at the center its heat blows away lighter elements like water and hydrogen but millions of miles further out from the star.

it is cold enough to bind these materials into gas giant planets like wasp 39b the huge gravity of the newly forming star pulls the gas giant closer and closer over millions of years eventually the gas giant ends up so close that it becomes a hot jupiter astronomers believe that many of the hot jupiters they find in orbit around alien stars made the same journey this death spiral could be one reason why future space travelers might find few rocky planets that could be our next home a jupiter-sized gas giant begins its journey towards its star it steamrolls everything in his path it’s possible that it swallows smaller planets whole a jupiter-like planet’s huge gravity smashes other planets together and sometimes kicks them out of the system entirely the planet eventually settles into a close orbit as a hot jupiter but it leaves a trail of destruction in its wake runaway gas giants could be responsible for the annihilation of smaller rocky planets and systems across the galaxy it might be one reason why earth-like exoplanets
prove hard to find a hot jupiter migrating towards its host star could wreak absolute havoc on the inner regions of an early solar system honestly this ultimately comes down to the universe being a fairly unforgiving place it’s found many creative ways to make a solar system completely uninhabitable hot jupiters smash potential future earths before they have the chance to flourish but those planets that do escape the destruction can fall victim to other world killing phenomena our own solar system shows future space
travelers what disasters can ruin promising rocky planets [Music] venus is earth’s twin both planets are roughly the same size and they contain almost identical elements in the same proportions on paper these characteristics make venus a good candidate to support life the reality is very different venus is the hottest planet in the solar system the surface temperature tops a scorching 860 degrees fahrenheit that’s hot enough to melt lead and corrosive clouds of sulfuric acid blow through its atmosphere have you ever had one of those days
where it was just so hot and humid that you go outside and it feels like it’s stinging your skin well venus is a lot worse than that imagine that only you’re in a fire and people are pouring acid on you humans searching for a new home in the future could detect that a venus-like exoplanet has many of the right ingredients to be a habitable world just like earth it might have the correct elements to support liquid water an oxygen-rich atmosphere and potential life forms venus is in many ways much like the earth it’s about the same
size it’s a rocky planet billions of years ago it probably looked a lot like the earth that had an atmosphere like we did it may have even had liquid water on its surface why did venus transform from a potentially habitable planet into a scorching hell [Music] a clue lies in the data that the venera missions beam back to earth the venera landers captured the only photographs ever taken of the surface of venus these images show the hellish baked planet up close the instruments on board the landers record that the atmosphere of venus
is 95 carbon dioxide it is the quantity of this gas that explains why the planet is so hot carbon dioxide is a greenhouse gas light from the sun can warm the surface but the carbon dioxide absorbs that warmth and won’t let it escape back into space so it’s insulating the planet and the planet just gets hotter and hotter and hotter carbon dioxide makes up just 0.4 percent of earth’s atmosphere this small amount of carbon dioxide in the air allows our planet to radiate excess heat into space and stay cool if venus and earth are twin planets born with almost identical elements in roughly the same proportions then how did venus end up with so much carbon in its atmosphere  and what turned the once vast oceans of mars into frozen deserts  our days on planet earth are numbered a billion years from now humans must find a new home in another part of the galaxy but how will future space travelers make the right choice when selecting the next planet to move to today astronomers learn a valuable lesson from earth’s twin venus venus and earth were born with the same elements and roughly the same proportions but unlike earth venus is now a burning hell with a suffocating carbon dioxide rich atmosphere how did two planets that started out so similar end up so different a clue lies in where earth stores its carbon four billion years ago mega volcanic eruptions release huge amounts of carbon dioxide into earth’s atmosphere water droplets inside clouds dissolve this carbon dioxide and carry it back to the surface as rain rivers flow to the oceans and some of the dissolved carbon dioxide reacts with other elements to make calcium carbonate solid calcium carbonate rains down on the ocean floor and helps to form limestone rocks that lock away the carbon dioxide this cycle over many millions of years packs almost all earth’s carbon into the planet’s crust but venus turns this process on its head what triggers a planet like this to release so much of its carbon from its rocks into the atmosphere astronomers believe that a clue lies in the light from groups of thousands of stars called open clusters telescopes measure the brightness of the different stars in these clusters these observations reveal what could bake an earth-like planet to death the light from middle-aged stars is much brighter than the light from young stars of the same size and type scientists think that the reason why these stars get brighter as they age lies deep inside their super hot cores a star heats up and gets brighter as it burns through its nuclear fuel supply astronomers calculate that our sun was both 30 percent cooler and dimmer four billion years ago our understanding of stars tells us that in the past the sun was not as bright as it is today that means that the planets would have been bathed in less radiation so venus probably would not have been as hot it may have had rivers and oceans and it may have been a place that could harbor life venus shows future humans how an aging star like our sun can wreck a promising planet over the sun’s lifetime nuclear fusion inside its core generates more and more energy which builds up in the surrounding hydrogen shell the star heats up this extra heat warms the surface of venus 125 million miles away the oceans on the planet evaporate and the atmosphere fills with water vapor this traps heat that bakes the rocks and forces them to release their carbon this triggers a runaway greenhouse effect that pushes surface temperatures to over 860 degrees fahrenheit venus shows how an aging star can transform the atmosphere of a habitable candidate planet into a thick suffocating nightmare our solar system contains one more example of what a rocky planet in the habitable zone of a distant star might be like and it serves as another warning to future humans looking for their next home mars is around 75 million miles further away from the sun than venus probes and rovers sent to the red planet confirmed that it appears to be a dead frozen world but new evidence reveals that mars was a very different place billions of years ago the mars reconnaissance orbiter takes super detailed images of the martian geology these photographs reveal the telltale signs that water shaped much of the landscape of mars at one time mars had river valleys that were full lakes that were full it was raining it was snowing it was very much like earth over time this wonderful earth-like world that was friendly to life turned into a dead cold desert what happened to mars nasa’s maven spacecraft uncovers a clue in 2017 maven monitors the atmosphere ofmars the probe discovers that each year around 35 000 tons of gas escapes into space from the atmosphere of the red planet every single second that takes by mars is shedding a little bit of its gaseous atmosphere into the void of space and that’s like stealing coins from a cash register every single day each individual theft is pretty small but the amount really adds up over time the thinning atmosphere of mars lowers the planet’s atmospheric pressure and liquid water boils away the atmosphere cannot trap heat to warm

the planet in the past mars has what it takes to be a viable habitable world what is robbing the red planet of its gas and can mysterious mega geysers millions of miles from earth redefine the search for a habitable planet [Music] humans in the future must find a new home and another part of the galaxy astronomers today scour the cosmos for planets that can support complex life but our solar system contains a warning about how the galaxy can wreck habitable worlds what transformed the oceans on mars and to barren deserts
the data from nasa missions to the red planet reveals a clue it shows that the magnetic field of mars is 40 times weaker than that of earth a planet’s magnetic field is its protective armor against the sun the sun blasts the inner solar system with an intense stream of radiation the weak magnetic field of mars cannot withstand this punishment the sun’s radiation rips away the martian atmosphere one molecule at a time astronomers think they know why the magnetic field of mars is failing the super-hot metal ball at the center
of the planet is cooling we think that the magnetic field of a planet is generated by its rotating hot molten core so the bigger the planet the bigger the core and the longer it takes to cool down the mass of mars is around 10 times smaller than that of earth this difference in size unlocks why the magnetic field of the red planet is so weak and it shows future humans looking for our next home what can happen if they settle a rocky planet that is too small one billion years after mars forms the planet is a water-rich world covered
in rivers and oceans around it is a protective magnetic field that emanates from its churning molten metal core but mars is so small that it loses heat quickly and solidifies from the outside in the core hardens and the flow of metal slows disturbing and weakening the magnetic field when this planetary shield fails completely it exposes mars to the scorching solar wind energy from the sun strips away the martian atmosphere and the liquid water on the surface of mars evaporates into space if you would have visited our solar
system billions of years ago both earth and mars would have been these beautiful blue planets but then if you came back today you realize that something really changed mars had gone all wrong and the difference between the two planets one habitable and one probably not is the mass mars warns humans searching for a second earth how the galaxy can wreck viable planets in the habitable zones of stable stars we look around our galaxy and our solar system we see that the ingredients for life are everywhere but you need more than
just the ingredients you also need the right conditions the universe is a violent place so being in a habitable zone does not guarantee your safety liquid water is the key to sustaining complex life long term on another planet  but where outside the habitable zone of an alien star can humans in the future find water in its liquid form when scientists first came up with the term habitable zone they were thinking about how close a planet had to be to its star to be warm enough for liquid water but perhaps we need to look farther out
perhaps we’ve missed something nasa’s cassini probe uncovers a clue cassini studies the giant planet saturn and its moons in 2015 the probe takes this photograph of a frozen moon called enceladus it shows mysterious plumes blasting out at over 750 miles per hour from icy cracks in the moon’s crust cassini grabs a sample from one of the plumes analysis reveals that it contains tiny grains of water ice and salty water vapor this evidence leads scientists to a startling conclusion it is likely that only liquid water
under pressure inside enceladus could blast out these plumes from the surface of the moon and the huge quantity of water in each plume is evidence that they could come from a giant saltwater ocean locked inside enceladus when you stand on the beach or take a boat out into the ocean it seems like it’s vast it’s just a huge amount of water out there but in fact it’s only a tiny percentage of the total amount of mass of the earth on enceladus liquid water makes up a quarter a quarter of that moon’s total mass enceladus is around 750 million miles outside the habitable zone of our solar system how is it possible for this moon to be warm enough to contain liquid water and how does this heat transform the search for our next home  world humans in the future must search beyond our solar system for a new home world the galaxy snaps the odds against the existence of the second earth in the habitable zone of an alien star today scientists hunt outside the habitable zone for signs of liquid water the key for sustaining complex life long term they find a secret ocean hidden below the icy shell of saturn’s moon enceladus how is it possible for a moon over 900 million miles from the sun to contain liquid water astronomers believe that the answer lies with the huge gravitational power of saturn saturn’s immense gravity squashes and stretches enceladus as the moon orbits on an elliptical path this constant warping of the moon’s rocky core creates friction and a huge amount of heat as this heat radiates outwards it melts the lower layers of the moon’s icy shell
to create a subsurface ocean cracks appear in the sea floor hydrothermal vents form in these gaps and pump minerals from the core into the ocean it’s pretty amazing when you think about it being way out of the habitable zone having a completely frozen surface and yet still having a warm salty ocean that is cool astronomers believe that our galaxy could contain a hundred times more moons than planets it is likely that there are trillions of moons in the milky way a watery moon heated by the gravity of a huge planet
could be a viable new home for humans in the future i remember when the idea came up that there could be under surface oceans on these icy moons and how amazing that was but the thing is there are more icy moons out there than there are rocky planets if we’re looking for liquid water whirls maybe we should be looking for icy moons of gas giants if a giant alien planet is close enough to its star and its water-rich moon has a thick atmosphere to protect against radiation then it is possible for the moon to have
liquid water on its surface this moon could look like earth the moons in our solar system that have liquid water oceans are all in the outer part of our planetary system they’re very very cold but what if we find a system out there that has a massive planet closer into the star now its moons are warmer they actually could be earth-like there could be atmosphere there could be ocean there could even be life on exo moon this isn’t science fiction this is actually entirely possible imagine standing on this lush world and looking up into the sky and seeing not only your sun but this enormous planet that you’re orbiting feeling half the sky nasa’s new james webb space telescope promises to revolutionize the search for alien worlds this next generation observatory will help astronomers study distant planets and their moons in more detail than ever before it is possible that the discovery of a habitable earth-like planet could be just around the corner just a few decades ago we didn’t know of any planets around other stars
and someday in the future people will talk about this time and say they didn’t even realize there were other earths out there things change fast it’s wonderful to be along for the ride [Music] today’s astronomers see a galaxy that is a violent unpredictable place flares from super huge stars fry planets instantly gas giants smash smaller rocky worlds to pieces solar radiation makes planets alive and strips them of their atmospheres what is for sure is that the universe does not make it easy for life to thrive
some of these so-called habitable exoplanets might actually be these totally uninhabitable alien hellscapes but today’s astronomers think that the galaxy contains many viable planets that future human travelers can make their homes even though we know of a lot of exoplanets and very few of them are potentially earth-like that doesn’t mean there aren’t lots of earth-like planets out there there are hundreds of billions of stars in the galaxy and planets with conditions like our own are hard to detect for us right nowso there could still be billions of earths out there our future home could be a rocky planet around a sunlight star it could be an ocean moon orbiting a gas giant there are trillions of candidates in our galaxy our next home is out there just waiting for us to find it.