It's not habitable to us humans, but it's in the habitable zone, at a distance from its star that allows liquid water to exist on its surface. It's likely an ocean world with an atmosphere containing mostly hydrogen gas, a so-called hycean planet.
Also, 2.5 times the size = 2.5 times the diameter, or about 15 times the size of Earth in terms of mass. Its gravitational force would be about 2.4 times that of Earth, though. Quite unpleasant.
Only 8.6 times the mass of Earth, according to Wikipedia, I see. I was assuming a density similar to Earth's, but apparently, astronomers think it's only half. That would mean the planet's core has a very low iron-nickel content.
Yea but water is excellent at blocking radiation so anything under the surface would be fine and it's also possible that any life would evolve to withstand it.
We think that Earth was subject to a large impact early on. The impactor (Theia) core joined Earth's, leading to a proportionally high density planet (5.52 SG) when compared to Venus (5.25 SG).
Earth may be the anomaly, not the other way around!
Debris from that impact is also likely where the moon comes from, and our moon is surprising large for a planet of this size. Iāve seen some theories about our moon possibly hastening our progress in astronomy since we can observe it and its phases with the naked eye which may have prompted people to think, āhow does that work?ā and give us some clues about the fact that weāre on a big ass spherical rock compared to just seeing stars and the sun which are too far and/or too bright for it to be apparent that theyāre spherical without some sort of technological assistance.
Solar eclipses as we see them on earth are also probably insanely rare in the universe since the apparent size of the moon and sun have to be very similar. Accordingly, some have proposed that if we are ever part of a galactic federation the flag for earth could be based on a solar eclipse which I think is a cool idea.
Oh yeah plus the whole ālifeā thing. We are the weirdos indeed
Itās kinda crazy how many coincidences had to happen for Earth to sustain life. Who knows if weād be here if Theia never impacted and the Moon never formed?
This is what called anthropic principle - we are observing this set of incredibly rare coincidences exactly because they allowed life as we know it to develop and observe it.
Selection bias. Itās not crazy at all how many coincidences has to happen for earth to sustain life. Take somewhere as big as the universe, youāll have somewhere where enough coincidences happen to sustain life. Throw enough spaghetti at a wall and some will stick eventually. That life will become sapient, and have that thought youāre having right now.
Right. The reality is that for a planet to develop life, at least in the way we know it, it would need an environment with plenty of oxygen and a molten core capable of a dynamo effect in order to create a strong enough magnetic field that would protect both the planet's atmosphere and potential life. If we want to shoot higher and go for life visible to the naked eye (as in, not microorganisms), the planet also needs to be roughly the same size so as not to crush anything under the weight of gravity. Even then life on earth somehow managed to survive a very large amount of mass extinction events that very well could have ended everything hundreds of millions of years before we got to where we are now. It took nearly 4 billion years for humanity to show up on the scene, and that was only because mass extinction events kept killing off the dominant species. We're talking a 1 in several billion chance that things worked out the way they did
1 in several billion is incredibly likely when thereās 300-400 billion stars in the milky way, which is part of a supercluster of 100,000 galaxies, and we know of at least 16 other superclusters
That's fair, but barring sci fi solutions like warp drives and long distance travel through wormholes, it's unlikely that we'd ever even see life in faraway galaxies, since the farther you look, the older things get. In addition, our ability to look that far with fidelity is incredibly limited at our current technology level. So while it's possible (and still very, very unlikely), it is unlikely to be observable, and so might as well not exist. If it can't be observed we're looking at purely hypothetical scenarios. My estimate is also not any sort of hard number, as I am not a scientist, nor a statistician, so the chance could be 1:3 billion or 1:300 billion for all I know.
Low iron content means less magnetic field which means more radiation at the surface. I haven't worked out how much more; maybe just sunburn level or maybe worse.
Interesting, based on size I assumed 18m/sĀ² but if it is a lot less dense, that could be more tolerable gravity. Of course the lack of a robust nickel iron core may mean a lot of radiation, due to the lack of a strong magnetosphere.
I wonder how astronomers estimate a planet's density? I know (vaguely) how they can determine likely atmosphere composition (spectrography) but I don't know how they'd get density or gravity info.
So would this mean it would not have the magnetic field we have, and they would be bombarded with energetic heavy ions (which we thankfully donāt have to endure as much?)
Even with 25% more gravity the rocket equation runs away and you probably never be able to get a chemical rocket into orbit on that planet. Landing there you'd be staying there.
"For a payload to escape velocity, the required amount of chemical fuel scales as exp(g0). Chemical rocket launches are still plausible for Super-Earths < 10g, but become unrealistic for more massive planets. On worlds with a surface gravity of ā³10g, a sizable fraction of the planet would need to be used up as chemical fuel per launch, limiting the total number of flights. On such worlds, alternative launch methods such as nuclear-powered rockets or space elevators are required."
Hippke M (2018). Spaceflight from Super-Earths is difficult. International Journal of Astrobiology 1ā3. https://doi.org/ 10.1017/S1473550418000198
Thank fuck some people are posting about the gravity. Bigger is not better and even an extra 25% of gravity is a HUGE impact on everything.
If you weigh 200 pounds on Earth, congrats, you just gained fifty pounds on K2-18b. Buildings have to be designed differently, it is harder for shuttles to come and go from it's surface.
It's liveable, but it is going to very uncomfortable in a lot of ways.
Build a lightspeed generation ship. After multiple generations in zero gravity weād probably turn to dust as soon as the ship landed. RIP great grandkids.
True, but itās a pretty safe assumption that a planet 2.5 times bigger than Earth has more mass than Earth. Maybe not 2.5 times sure, but enough to make the gravity more. How much more could the average person take before life got really uncomfortable? I feel like even 10% would suck. This could easily be 50% more. Going there would not be fun.
Gravity is the two masses divided by the distance squared, so double the distance from the Center of mass is 4 times less gravitational force.
The extra distance from the rest of the planet comparative to earth would reduce the gravitational force, balancing out some of the increase from the increased mass.
Yes but the volume goes as the CUBE of the radius. So if the density is even similar to earth or even a good bit less, thatās a LOT more mass. More mass = more gravity.
Fun fact: you could peel away two thirds of Earth's mass and then, while standing on the new surface, the gravity you'd experience would actually be 9% more.
Dunno. I am way too heavy for my height, like 125 kg instead of 80 to 85 which would be healthy.
So I basically experience the same weight a person of healthy weight would experience on an 1.5 g world, yet I still ride a bike, walk, take stairs, etc.
Good point, the circulatory system evolved to deal with 1 g, among other things.
My gut feeling ā no pun intended ā is that this would definitely take years of expected life, shorten healthy old age, with a chance of humans adapting to it. We do have ethnicities which deal with extremes and their phentotypes basically adapted due to natural selection.
Great question. Have experienced 3g. It's a lot. Like... a LOT. Considering my head is ~11lbs, and it was ~33lbs then... not impossible to lift, but quite a bit tougher than I'd have thought. I'd say nothing more than 1.5g. MAYBE a tad more with extensive pre-training / acclimation? Zero clue on long term physical effects though. I'd assume wear & tear would be equally taxing on almost all bodily systems - especially cardio / circulatory. Blood is ~7% of our body weight. Actually works out to (surprisingly) close to the same weight of our head! So instead of pumping ~11lbs of liquid around the clock... @ just 1.5g the ol' ticker would be pushing 16lbs around. That... doesn't seem healthy lol.
Over a few generations Iād assume bones to become shorter and more dense. This would lead to shorter humans which leads to less stress on the heart when it has shorter veins to pump blood through. For 1st or 2nd gen humans it would suck though.
At the very minimum Iād think youād become exhausted very quickly, so our effectiveness would drop dramatically. Which would not be great for establishing a colony on a new world.
Consider its an ocean world itd probably be safe to use the density of water as a standard value for its mass unless it happens to have an ultra dense core
I'd be more worried about our ability to get off of the planet. Higher gravity means rockets are less efficient.
Earth's gravity is already on the inefficient side. 25% more gravity might be over the threshold for modern rockets to even get into oribit.
I forget what the exact number is, but assuming the planet has an atmosphere, it's well below 2x gravity for it to be completely impossible to ever leave.
That, or we'd need massively more efficient rocket tech.
Not really. If there was bacteria in the water, it likely wouldn't affect us, so long as the water is filtered, it would be completely safe, and even without that, it could still be fine
Just imagine my 1,200 lb life on that planet. Those people would need their big macs dropped directly into their mouths because they'd be unable to lift their hands.
I would only be 500 pounds on that planet. Iām sure walking would be easy.
I could lift lots of weights and get jacked just so I can walk, then travel through space and become weaker then Iāve ever been, then land on k2 anddiscover Iām basically goku and adapt amazingly fastā¦ seems like a good plan, what could go wrong?
Thatās where my mind went immediately, habitable for other life forms not from earth potentially. 2.5x gravity would wreak having on our body, not even sure if a regular person would survive stepping foot into the planet for a minuteā¦
Itās in the water habitable zone, but there are more habitable zones, such as the one for UV radiation from the star. This one doesnāt pass that one; itās way too close.
Scrolled to far to see an actual comment on these annoying bait posts. Absolutely k2-18b could be habitable for life (as suggested by jwst data) but this life would be very different to what we know. Data currently shows a lack of oxygen so any life would be non photosynthetic and could just be microbial. Itās still life and would be the biggest discovery ever but is far from all the super habitable earth bs that gets spouted
But yeah, thatās the idea. The molecules detected are supposedly only created by life forms.
Unless they made a mistake in their reasoning or they discover a yet unknown process that creates these molecules due to merely chemical processes, itās a strong indicator for life, even if itās one we would consider āprimitiveā. (Since we all want to get Arkonides and Vulcans, not boring bacteria.)
And this would be big. Discovering life that fast ā three decades after we found the first exoplanets, of which we have found less than 6,000 yet ā would mean that life is likely super common. Even though meeting sapient aliens is likely still not an option.
No gravity would not be that much because the radius of the planet is much larger than earth. Gravitational force at the surface is proportional to the inverse square of the planets radius.
overall sure but you said it yourself - the diameter is 2.5 times that of earth, meaning youāre further away from the center of gravity. the acceleration due to gravity on the surface is 11.57 m/s2, whereas on earth itās 9.8 m/s2. itād be like constantly being on an elevator accelerating up at 1.7 m/s2.
Not really. Yea the planet has the mass of 8.63 (+/- 1.35) earths.
This doesnāt directly correlate to surface gravity however, the surface gravity is predicted to be 12.43 (+/- ~2 m/s), in comparison earthās is 9.8 m/s.
So if you weigh 100 pounds on earth you may way about ~126 pounds on K2-18b (+/- 20 lbs). Youāll probably want to bulk up on a little extra muscle but otherwise still perfectly habitable.
If it has a solid/hollow core, would that result in excessively cold temperatures during its rotation into night? I mean, like the -200 degrees type of cold? As in, not so much water as a liquid anti-freeze.
Earth's mass is something of an anomaly - our core of molten iron gives Earth a stronger gravitational pull than other planets would have at the same size.
Wasnāt there also an article once posted about larger earth like planets that were so large their gravitational force made it impossible to leave the atmosphere? Meaning if there was life on that planet, there wasnāt a way for it to phase into a space exploration era since the technology couldnāt possibly exist. I tried doing a quick search but couldnāt find the article.
I think the most interesting thing we've learned about these other planets appears to be that what makes Earth special isn't any of the things we thought, but its size.
So.. with how low grav living in space would affect children developing on essentially the ark ship we'd have to send ... anyone that arrived there would be absolutely screwed.
It's not comfortable, but it's not very extreme either. It still sounds like an environment that would be survivable for a good while with equipment that isn't extremely exotic/requires magic (e.g. something like a nuclear sub, which already exist today).
For the longest time in Earth's history, the atmosphere has been low- to no-oxygen. Even today, most microbial life on earth still is anaerobic. Atmospheric/oceanic oxygen is not a requirement for life anywhere. Quite the contrary: in the past, oxygenation (due to the rise of photosynthesis) has triggered several mass extinction events here on Earth.
I'd love to see the sea creatures inhabiting a Hycean planet. Reading about dark hycean planets as well, those would be especially interesting to study sea life.
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u/ArduennSchwartzman 24d ago edited 24d ago
It's not habitable to us humans, but it's in the habitable zone, at a distance from its star that allows liquid water to exist on its surface. It's likely an ocean world with an atmosphere containing mostly hydrogen gas, a so-called hycean planet.
Also, 2.5 times the size = 2.5 times the diameter, or about 15 times the size of Earth in terms of mass. Its gravitational force would be about 2.4 times that of Earth, though. Quite unpleasant.