Habitable Exoplanets | In Search of Earth 2.0

the Earth similarity index or ESI is a Formula designed to boil down various planetary characteristics into a single understandable number that we can then use to compare another planet to the Earth after all this is the only place that were 100 confident that life exists so if our goal in searching the cosmos is to discover alien life or even a second home for Humanity our best bet will be finding a planet akin to our own and let's be honest only a few hundred years into industrialization and we're already altering the planet in some dramatic and dangerous ways it's not entirely bizarre to think that one day whether it's decades centuries or Millennia away one day we will need to leave and find a new planet preferably one similar to this one to call home the only problem with using ESI as a metric is that Earth-like doesn't necessarily equate to habitability as it's possible for plants to be even more habitable than Earth which would simultaneously almost paradoxically make it less Earth-like to mitigate this disparity between Earth likeness and habitability I've taken the Earth similarity index and cross-referenced it with the conservative list of potentially habitable exoplanets the result is a list of only the most habitable and most earth-like planets discovered to date or in other words 16 candidates for Earth 2.0 foreign foreign up is Kepler 186f with a radius measuring only 11 percent larger than the Earth's when it was first discovered all the way back in 2014 this was the first earth-sized exoplanet to ever be discovered orbiting within its star's habitable zone however because the planet belongs to a much smaller and colder Red Dwarf star the habitable zone occupies a much tighter area between 0.23 and 0.46 astronomical units orbiting at 0.4 a u this puts Kepler-186f on the cold side of its star despite this being roughly the same distance Mercury orbits around the Sun 186 F still only receives 30 percent of the illumination compared to the earth making this a dim world as well if water is in fact present on the planet in large quantities most of it would likely be tied up in tremendous polar ice caps relegating the habitable portion of the planet to the equatorial regions where large lakes may be able to form here life would be more than possible but being a world bathed in the red light of a red dwarf a plant life would need to adapt on Earth nearly all photosynthetic life takes on a green color to reflect roughly where the Sun's light peaks in order to avoid receiving damagingly high levels of light plants on Kepler-186f however would want to filter out the more reddish light supplied by its star replacing green chlorophyll with a red or even purple pigment such as anthocyanin as we'll see over the course of this video red dwarfs serve as some of the most frequent host stars for potentially habitable exoplanets meaning it may in fact be more common to find red and purple plant life than the familiar green overall despite its perceived High habitability Kepler-186f earns an ESI score of only 0.64 compared to Earth's 1.00 that's a 64 match which is good but we can definitely do better while it might be easy to wish this planet was any closer to its star that might not be the best idea as it's thought that 186f orbits close enough to potentially be become tidally locked or in English one side of the planet always faces directly towards its star and the other side faces permanently away while this isn't necessarily a death sentence it makes inhabiting a planet far more complicated than normal this brings us to captine B orbiting at only 0.17 Au this gives the planet an exceedingly high probability of tidal locking the biggest effect this has on the planet is how heat is distributed across its surface on Earth our rotation exposes all sides of the planet equally to the sun leading the equator to receive the greatest amount of heat energy and the polar regions to receive the least on a tidally locked Planet like Captain B however one side sits in Eternal nighttime usually resulting in a frozen Wasteland where nothing besides ice crystals is capable of growing on the other side instead of an equator the sun's energy comes to a focus where continual daytime sense surface temperatures to scorching levels while typically this makes the focus as uninhabitable as the other side somewhere between the freezing cold and scorching hot ambient heat and partial exposure to sunlight can induce moderate temperatures and to generate a narrow region of habitability living here the sun would be an eternal sunset with the skies split between a light side and a dark side mountain ranges in this Twilight Zone would be ideal for habitation as their faces would receive light and heat up their adjacent valleys while shielding any life from the constant onslaught of radiation one easy way to tell if a planet is tidally locked is to look at its clouds because heat is focused at a single point here you'd get a constant stream of warm air Rising drawing in more dense cold air from the darker side as this warm air rises it will cool with any moisture condensing out into clouds resulting in a radial pattern emanating outwards from the focus this one directional air circuit would help in the distribution of heat around the planet bringing warm air to the cold side and cold air into the warm side helping to widen the zone of habitability on the surface overall keptine B earns an ESI of 0.67 which admittedly still isn't very high making up for this is the fact that captime is only 12.8 light years away making a visit here slightly more possible than for instance Kepler 62f which orbits a star some 1200 light years away if you've been wondering how the names of these planets work Kepler 62 refers to the central star with each planet in the star's system being assigned to letters based on their position so a planet ending with f means that there's a coupler 62b 62c 62d and 62e before getting to 62 f with so many planets packed in it's no surprise that 62f is relegated to The Far Side of the star's habitable zone making it another cold world this might not be such a bad thing however given how big the planet is at over 1.4 Earth radii at this size the planet would be much more likely to have a molten metal core the benefits of which not only being the capacity to propagate a strong magnetosphere capable of protecting the surface from potentially damaging radiation but also powering robust geologic activity helping the planet to build an atmosphere through volcanic outgassing and generate a greenhouse effect to hold on to what slight amount of heat energy comes the planet's way ultimately kepler-62f's habitability all boils down to how thick of an atmosphere it has with calculations showing that at least five Earth atmospheres of carbon dioxide would be needed to sufficiently trap enough heat to melt ice on its surface all of this considered kepler-62f earns an ESI of 0.69 and it's at this point that we've reached an important distinction in our rankings as Mars has an ESI of 0.70 this gives us not one but two points of reference and places all the upcoming planets somewhere between these given that we believe Mars could have supported biologic activity earlier in its life this means the planets that fall within this range all have a very good chance of being able to do the same this brings us to Kepler-22b with an ESI of 0.71 here we'll find a planet that is only marginally more Earth-like than Mars at over 2.4 times the size of the Earth this starts getting into territory of what we'd call a super earth based on computer models if Kepler-22b features an atmosphere of similar composition to the Earth's average surface temperatures here would reach around to 22 degrees Celsius only slightly warmer than the Earth's average of 15 degrees Celsius and very nearly equal to the average 20 degrees Celsius experienced by Earth during its early Carboniferous period not only does this place 22b comfortably within the habitable zone but also means liquid water on the planet's surface is not just possible but rather probable however warm temperatures are only one of two conditions necessary for liquid water to exist on the planet the other being willed the presence of water which isn't always a given you see the amount of water a planet has is often determined early in its creation if a planet is lucky it could end up like Earth and receive an intermediate amount of water leading to the creation of both marine and terrestrial environments but if far less water was available in the early days of planetary formation an entirely terrestrial environment could result without enough water to form stable liquid bodies the greatest concentrations of moisture on the planet would be found within this soil a proper map of a world like this would replace oceans with vast pools of mud swapping out continents for extensive areas of routinely dry ground and in the place of large ice caps would be lands of thorough permafrost while these conditions might be less than ideal for the development of life if you know your soil science then you'll be aware that moist dirt is one of the best environments for a microbial life to thrive in and here on Earth it is within the soil that life becomes more abundant and diverse than any other ecosystem on the planet much the same would be expected of an arid world where any potential life could Prosper within the mud regions while avoiding the dry desert areas and Frozen poles here in the living mud pits microbial life could even flourish to the point of altering the color of the surface revealing where Blooms of biological activity are taking place within plant life isn't necessarily out of the question here either though it's unlikely something as dense and water consuming as forests would be able to grow and surface vegetation would more likely consist of moss layers and maybe some sporadic standing plants overall it's likely that desert planets and by extension living mud planets are far more common than planets like our own Earth and future space exploration might look less like meeting a bunch of cool smart aliens and be more about logging all the millions of different forms of microbial alien life and choosing the best ones to farm but as our exploration of exoplanets continues we'll likely find that a wide spectrum of planetary moisture contents exists ranging from a planet with only a few meager and seasonal mud collections to more established wet spots eventually to the point where small pools are able to form than Lakes all the way to Oceans however with hydrogen and oxygen being the most abundant and third most abundant elements in the universe water is by no means a rare substance cosmically speaking this means that as likely as it is for a planet to receive far less water than the earth it's also possible for a planet to receive far more water too in fact in all likelihood both fully desert planets and fully ocean planets are more common than Earth-like mixes which require a precise balance between the two wear Kepler-22b falls on this spectrum is unknown though based on its size and mass some suspect the Planet could actually fall further onto the ocean side of things for a true example of an ocean world we can move over to our next planet wolf 1061c which has been modeled here as such though I should make it clear that without further study we can't say for sure what the atmospheric surface or Oceanic conditions of any of these planets truly are orbiting extremely close to its parent star at 0.084 astronomical units this is almost certainly another tidally locked Planet though with a Luminosity of less than one percent of that of the sun this puts 1061c just within the inner edge of habitability now even though we've looked at a tidally locked Planet already the addition of a super ocean reaching many miles deep at its shallowest gives us more to talk about for starters water is a much better regulator of temperature than air and so warmth would likely be far more evenly diffused across the planet compared to a solely terrestrial body while temperatures at the focus may still prove far too hot for life and even create a zone of spontaneously boiling Waters like other tidally locked planets there would assuredly be a ring somewhere between the hot and cold extremes where life could potentially inhabit if Earth's oceans are any indication so long as the water isn't Frozen it can support life meaning marine life could likely even survive on the night side of the planet so long as the water hasn't turned to ice besides this however there'd likely be another line of potential habitability not one at any specific longitude but rather one at a specific depth you see on a super Oceanic world like this no matter how Direct to the sunlight is with Ocean's miles deep eventually the water would obscure it and cool down this would lead to another temperature gradient deepest directly below the focus and Trend closer and closer to the surface the further away it gets until finally it joins the surface level habitable ring what this means is contrary to tidally locked terrestrial worlds a far larger portion of ocean worlds would be conducive for life and we could expect to find a tremendous diversity of biology in a place like this a major challenge for life on a super Oceanic world is that with oceans miles deep everywhere there'd be no surfaces for plants to cling to while still receiving light the name of the game here would therefore be buoyancy where nearly all life would be responsible for keeping itself afloat indefinitely photosynthetic life could come to rely on a pneumaticist type structures to keep a float like kelp does here on Earth animals would either need to employ swim bladders or carefully balance their body structures to remain neutrally buoyant but honestly there are so many tactics organisms could employ to survive in a place like this that it's almost impossible to pinpoint what exact evolutionary paths might be taken here overall the potential for life to exist on a planet like this supports wolf 1061c scoring an ESI of 0.76 next up we have kepler-452b at 1.5 Earth radii this would be another Super Earth and gets bonus points for orbiting a g2v type star which is a really technical way of saying the same exact type of star as our sun this means any plants we brought over would be perfectly suited to make use of the light coming in and any native plant life here has a good chance of being similarly pigmented to ours though there is one big difference between kepler-452 and our sun and that's the star's age being approximately 6.5 billion years old 2 billion years older than our sun the star has already begun to expand in what is the beginning of its death cycle while the size of the planet means 452 B would likely be more than able to protect itself against its Sun's increasing radiation load for the next couple hundred million years as the star continues to expand eventually 452 B will be pushed out of its habitable zone and suffer a runaway green House Effect similar to what Venus is experiencing now making the surface far too hot to live on so while in the short term kepler-452b may be a promising Prospect if we wait until our own sun is dying 452b will already be long gone the opposite can be said about kepler-442b here we'll find a world only 3 billion years old a full 1.6 billion years younger than the earth if biology here on 442b started and progressed at a similar rate that it did on Earth that would mean life would just be making its first steps from single cellular to multicellular it wouldn't be for another 250 million years that sexual reproduction would come about 700 million years until plants developed 800 million years until animals developed and 1.6 billion years before the first potential intelligent life emerged which on the one hand means we shouldn't expect to find any complex forms of life but on the other hand means the planet is up for the taking however we may have reason to believe that life wouldn't necessarily follow the same trajectory here as it did on Earth you see at 1.3 times Earth's radius this not only designates 442b as a super Earth but to some it also qualifies as super habitable now there are a number of parameters that go into classifying a planet as super habitable one of the most important of which I've already mentioned is the planet's size 442b's 1.3 times Earth's radius is thought of as ideal as this ensures the planet supports a strong magnetosphere geologic activity a dense atmosphere and even some form of plate tectonics as you'd probably expect the planet's orbit also matters and it just so happens that 442 Beast Falls smack dab in the middle of its star's habitable zone ensuring the presence of liquid water on its surface while also keeping far enough away to avoid a tidal locking what a planet orbits also matters with the ideal type of star not being a g-type star like our own but rather an m-type or k-type red dwarf like kepler-442 as their dimmer and colder burn translates into a longer burn giving them life spans between 18 to 34 billion years far greater than the 10 billion year lifespan of our own Sun this greater lifespan gives planets like kepler-442b much more time to develop and evolve their biology meaning that if we're patient life here will eventually catch up and even surpass the Earth assuming you know that it does in fact have life all of this together lands 442b at an ESI of 0.84 though at over 1200 light years away it's a good thing it has such a long lifespan as it might take us a while to get here for something a little closer to home we can move over to our next planet Proxima Centauri B if you couldn't tell by the name Proxima Centauri is very much within our proximity and is actually the closest known star to our solar system and by extension this makes the two planets orbiting it the closest known exoplanets to us traveling at light speed a trip from the Earth to this system would only take a little over four years making journeying here more of a possibility than just about anywhere else in the Galaxy miraculously if we did Venture here we'd find a Planet roughly the same size as Earth that orbits well within the habitable zone however if this all sounds too good to be true well it might be you see the parent star Proxima Centauri is what's called a flare star capable of randomly emitting huge amounts of radiation occasionally exposing Proxima B to solar winds over 2 000 times stronger than what we experience here on Earth at levels like this even a strong magnetosphere may not be enough to protect the planet's atmosphere from vaporizing away potentially leaving the surface exposed to the harsh environment of space while life is still theoretically possible here it would be relegated to the planet's subsurface which could offer just enough protection from the sporadic solar flares to Harbor simple life forms whether or not life could first emerge in an environment like this is another story overall despite these challenges these surface level similarities Proxima B shares with Earth earns the planet an ESI of 0.87 though this has a high likelihood of changing in the near future as being so close to Earth we may be able to observe the planet through the next generation of advanced telescopes and get answers to some of the most pressing questions we have if we want a planet with a bit more quiet of a host star but still pretty close to us we can look no further than gliese 273b otherwise known as light and B at a distance of only 12 years away 273b remains in our general neighborhood while managing to orbit what appears to be a very quiet star with a Luminosity of only 0.88 to that of the Sun in order to occupy the habitable zone light and B must orbit extremely close at only 0.09 Au likely tidally locking the planet though with such a peaceful star lightning B is likely able to have a substantial atmosphere greatly improving the planet's potential habitability to everywhere not directly under the focus or directly opposite all of this combined results in a planet with an ESI of 0.91 an exceptionally high score with only three other confirmed exoplanets ranking higher next we're traveling to Tea Gardens star very similar to Leighton here we'll find a small red dwarf only 12 light years away with a low level of activity what makes Tea Garden so special is that it hosts not one but two rocky planets within its habitable zone Tea Garden B and Tea Garden C in order for both planets to occupy tea Garden's narrow habitable zone they need to be relatively far apart from one another putting B far on the warmer side of the zone and see further on the colder side but here we'll find a good example of why a planet's earthlikeness doesn't always equate to habitability being on the cold side Tea Garden sees larger than Earth's size would likely help the planet trap more heat and support bodies of water making it overall more habitable while simultaneously less Earth-like in total earning the planet an ESI of only 0.68 despite its good chances for maintaining bodies of water on its surface meanwhile Tea Garden B Strays critically close to the inner ring of its habitable zone running the risk of excessive Greenhouse Heating and diminishing its chances of hosting a habitable environment despite this with a more Earth-like mass of 1.05 B earns an ESI of 0.95 the highest of any exoplanet discovered to date normally this would be enough to earn the status of Earth 2.0 but while I'm not convinced this just doesn't feel like the best we can do so finally it's time to talk about the trappist-1 system or what can only be described as the most remarkable Discovery in exoplanets to date with not one not two not even three but four planets orbiting within its habitable zone out of a total of seven comparing the position of the planets of the trappist-1 system to those of our solar system we'll see that while trappist-1b and C orbit Too Close even closer than Venus hits trappist-1d sits just ahead of Earth e comfortable between Earth and Mars and f and g falling slightly behind but still within their star's habitable zone with age lurking too far back starting with trappist-1g will find the coldest of the habitable Trappist planets analysis of the planet found it had a density 76 that of Earth a strong indicator that a large amount of the material constituting the planet comes in the form of water being on the colder side of things it's likely that most of this water comes in the form of colossal ice sheets covering the vast majority of the planet however chances are this and every other Trappist Planet are tidally locked meaning around the focus these ice sheets could thin out and even entirely thaw opening a small muddy area at the center of the planet where melt Waters likely run through to possibly feed into lakes overall this gives the planet the appearance of a hatching egg or an eyeball for an example of what a similar if slightly warmer Planet would look like we can move on over to trappist-1f the next furthest planet in the Trappist lineup here we'll find a similar eyeball Planet only being closer to the parent star the encompassing ice sheets have been pushed much further back opening a wider focused crater for more substantial water bodies to fill with an almost identical radius to Earth but only 68 percent its mass this is expected to be another water-rich world with calculations proposing the composition of the planet to be up to 20 percent water for a comparison water only makes up 0.02 percent of the Earth's mass meaning here on one F this great quantity of water would build ice sheets tens even hundreds of miles deep this makes me think that not only could sizable Lakes occupy the focus but rather a single huge ocean nearly as deep as the ice surrounding it making the planet essentially one big fish bowl for their differing sizes and compositions trappist-1 f and g are in esis of only 0.70 and 0.59 respectively meaning we can still do better so now we're moving on to trappist-1d again with a lower density than Earth D is also expected to Harbor large amounts of water though this may in fact be mostly in the gaseous form rather than liquid encasing the planet in a thick and swampy water vapor atmosphere more akin to Venus this however opens up an interesting possibility where the excessive heat of the planet's focus makes the day side utterly uninhabitable but generates a far more temperate climate across the night side of the planet here lakes or even oceans of water could be sitting in absolute Darkness providing a refuge for life steeped in fog and forever Under the Stars overall simulations of conditions on the planet are split between an Earth-like and a more venus-like world but either way the possibility for life is real and the planet earns a total ESI score of 0.91 finally this leaves trappist-1e with an ESI score of 0.95 together with Tea Garden B this represents the most Earth-like exoplanet discovered and confirmed to date we can see this reflected in where e is located back on our chart being situated slightly on the warm side of the habitability Zone just like us and with a size and density nearly identical to the Earth with a greater density the planet is less likely to contain the copious amounts of water that drowns out all its neighbors opening up the possibility of a surface mixed between terrestrial and Marine environments it's hard to imagine a planet so similar to Earth and composition and characteristics not being a suitable environment for life as well so take it in enjoy what's possibly the closest will come to finding an earth 2.0 [Music] altogether at only 40 light years away the trappist-1 system represents one of if not the best locations to resettle in the event that Earth becomes for whatever reason uninhabitable but if there's one takeaway from all of this it's that while there are a lot of other planets out there very few of them look anything like ours so maybe for now we should focus on taking better care of the only home we have hey everyone I know this was a much longer video than usual but frankly I didn't even get to include Half of the planets that I wanted to so if you enjoyed please let me know in the comments and specifically let me know about any other interesting exoplanets that I might have missed and should mention in a potential follow-up video if you want to make sure that happens you can check out my patreon to help support me and the channel to keep putting out videos and of course make sure to like And subscribe and see you next time thanks

Channel: Astro Pro

Views: 90,434

Keywords:

Id: bh-Qyibl0kU

Length: 27min 55sec (1675 seconds)

Published: Wed Oct 12 2022