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Can life emerge around a white dwarf?
- A_D_E_P_T 2y agoHmm. Interesting. A white dwarf is about the size of Earth -- roughly 1/100 the radius of the Sun. However, a planet in a white dwarf's habitable zone must be about 1/100 the Earth-Sun distance. (∼0.006 AU to ∼0.06 AU.) This dual scaling cancels out neatly. A white dwarf in that planet's sky would appear similar to the sun in our sky. White dwarfs are also indefinitely stable; they keep cooling over billions of years to become black dwarfs. Then, over >10^100 years, all elements heavier than iron will decay to 56Fe by various processes such as fission and alpha emission. All atoms lighter than iron combine by nuclear fusion reactions, building gradually up to 56Fe. All of this can happen via quantum processes at zero temperature. So they end as lumps of indefinitely stable cold iron. Intelligent life can hang around white dwarfs for a long time. Good candidate star type for Dyson spheres.
- surgical_fire 2y agoAt 1/100 distance, wouldn't a hypothetical planet be tidally locked to the white dwarf? Could tidally locked planets be suitable for life?
- cenamus 2y agoNot quite that close but Mercury seems to have an interesting interaction with the sun https://en.m.wikipedia.org/wiki/Mercury_(planet)#Spin-orbit_resonance https://en.m.wikipedia.org/wiki/Mercury_(planet)#Spin-orbit_...
- A_D_E_P_T 2y ago> At 1/100 distance, wouldn't a hypothetical planet be tidally locked to the white dwarf? Probably. Well, usually. If something gave that planet a very hard knock, it could spin up for a while, especially if it's around the outer limits of the proposed habitable zone. > Could tidally locked planets be suitable for life? Definitely. Depends how well they're able to redistribute heat from the hot side to the dark side. So atmospheric composition and water content (also the presence and extent of surface water) would be the decisive factors. You'd get wild weather, though.
- 867-5309 2y agoit's a hard knock white dwarf dust
- Loughla 2y agoThat's almost a joke. I don't know what to categorize that as. It isn't a pun. What is that?
- bovermyer 2y agoIt's technically a filk, just really short.
- thehappypm 2y ago“It’s a hard knock white.. dwarf dust!” Is the joke
- Loughla 2y agoYes. I understand. I was saying it's almost a joke. But for real what is it called when the things you're saying don't necessarily rhyme with the original phrase but have a similar cadence?
- thehappypm 2y agoThis does (nearly) rhyme
- bell-cot 2y ago> Definitely. Depends how well... I'm less optimistic. Between the fraction of the planet's surface that's suitable for life, the lack of tides, the (likely) lack of plate tectonics, and impairment of the various cycles ( https://en.wikipedia.org/wiki/Biogeochemical_cycle https://en.wikipedia.org/wiki/Biogeochemical_cycle ) - tidal locking to the star will profoundly degrade the planet's suitability for life. Tidal locking may also rule out having a planetary magnetic field. Though "protect the atmosphere" may not matter much, if said atmosphere (plus the water) has all condensed and frozen on the dark side of the planet.
- BurningFrog 2y agoOn a tidal locked planet, conditions should be very static. The point facing the sun is the hottest, and the opposite point is the coldest. Which means there is a constant "spectrum" of climates in between, and you only need one of these thousands of microclimates to be beneficial for creating life. So this may be the planets most suitable for life, if this theory I just made up has any validity!
- surgical_fire 2y agoIt does make some sense, even if life would be viable only in (for example) the twilight rim of the planet (such as around the poles)
- cma 2y agohttps://en.wikipedia.org/wiki/Eyeball_planet https://en.wikipedia.org/wiki/Eyeball_planet
- rybosome 2y agoI once read an article that speculated about this. The conclusion was that perhaps there could be a ring around the planet, at the border of the side facing the sun from the side facing away from the sun. That ring could be a habitable zone.
- AnotherGoodName 2y agoA large moon should absolutely mess this tidal locking up fwiw since it will have far more influence than the star just as our moon has far more tidal influence than our sun. Not that I think tidal locking is a blocker for life but it’s also not a big deal since large moons are extremely common and therefore the tidal locking is not guaranteed.
- khuey 2y ago> All of this can happen via quantum processes at zero temperature. So they end as lumps of indefinitely stable cold iron. Assuming no proton decay, of course.
- A_D_E_P_T 2y agoWhich has yet to be experimentally observed. At some point we'll be able to rule it out, I'm sure.
- jahnu 2y agoSorry if this is a stupid question. If proton decay does not happen, but a proton is say in motion through a galaxy, where does the energy for its gravitational waves come from? Its momentum and therefore it slows down?
- A_D_E_P_T 2y agoA lone proton coasting inertially through empty space at a constant velocity, even if it's moving quickly, does not generate any gravitational waves. It might generate gravitational waves if it's accelerated, but then those would come from the energy budget responsible for that acceleration.
- justsomeshmuck 2y agoIs it only accelerating objects that emit gravity waves/particles, or do decelerating objects do it too?
- ChrisClark 2y agoThat's the same thing
- soulofmischief 2y agoAcceleration is a general term for both increases and decreases in velocity. It might also surprise you to know that "incline" functions the same way.
- api 2y agoWhat I love about the idea of planetary systems around dwarf stars is that if the planets were close it would make interplanetary flight quite a bit faster and easier. Now imagine multiple ones with life. Someone out there in the vastness of the cosmos might be LARPing Buck Rogers or Commando Cody. Simple rockets could take you everywhere. It’d be like The Expanse but without the physicists nightmare fusion torches. Such things can maybe be built but it’s many orders of magnitude harder. These folks could be living the dream with 1950s level tech. They probably look like crabs though.
- wruza 2y agoAlso due to tidal lock “weather” they can simply kite their satellites (and rockets/missiles) to the orbit, for the most part. You open the hatch and let it fly. Don’t forget to close the hatch though, or your entire dream will fly too.
- api 2y agoWhoa… I never thought of that. If complex life were possible on a tide locked planet that held onto its atmosphere you could ride the powerful currents this would create at least much of the way to orbit. You’d probably need a rocket to reach orbital velocity and escape but the atmosphere might be almost like your first rocket stage. Such a civilization would also have endless free energy via solar harnessed from the sun side and continuous prevailing powerful winds. The latter would probably get tapped first. Huge wind turbines would just always spin. This would be true from their dawning of industry, which would be interesting. No energy wars. I’m sure they’d find something else to fight about if they were aggressive and territorial like us.
- cruffle_duffle 2y agoWouldn’t the amount of habitable land mass on a tidal locked planet be rather small? Like the bulk of the planet is either hotter than hells freezer or colder than its hot tub. You’ve got only a fixed ring of land that would be usable. Unless life can survive & thrive in the remainder. Which I’m sure it can and does.
- jajko 2y agoWouldn't gravity tidal forces rip those planets eventually apart? Like we expect ie Phobos to end up, and Mars has much gentler gravity gradient than this would have. Or would tidal locking somehow prevent it?
- wiml 2y agoI think even for a white dwarf the Roche limit is well inside the inner edge of the habitable range. So a planet that gets torn apart by gravity would already have been uninhabitably close.
- pavel_lishin 2y ago> Intelligent life can hang around white dwarfs for a long time. Good candidate star type for Dyson spheres. I would imagine that if intelligent life can build a Dyson sphere, it can probably travel to different stars as well.
- 082349872349872 2y agocompare Forward, Dragon's Egg (1980)
- cheela 2y agoFor reference, https://mdpub.github.io/cheela https://mdpub.github.io/cheela
- 082349872349872 2y agowhile we're at it*, RLF82: "Flattening spacetime near the Earth": https://journals.aps.org/prd/abstract/10.1103/PhysRevD.26.735 https://journals.aps.org/prd/abstract/10.1103/PhysRevD.26.73... * (and I am admiring the specificity of that HN acct)
- thechao 2y agoOr, more directly, Niven’s “The Smoke Ring” about humans living directly in an oxygenated accretion disk around a white dwarf.
- ossopite 2y agoI think you wrote compare forward as a long version of cf., but I believe cf. is actually short for the latin confer
- 082349872349872 2y agoForward is the author :) https://en.wikipedia.org/wiki/Robert_L._Forward#Fiction https://en.wikipedia.org/wiki/Robert_L._Forward#Fiction note wrt to comment elsewhere in this thread that Forward was also involved with physical aspects of the Integral Trees/Smoke Ring world build.
- pfdietz 2y agoThe orbital speed of such a planet would be extreme, something like 300 km/s. This also means other planets (like Venus or Mars are to Earth) would be visible in the sky as perceptible disks.
- perihelions 2y agoIt's the same scale as the orbits of the large moons of Jupiter (roughly 0.003 au–0.013 au). If you were standing on one of those, the others would appear as very large disks—some of them larger than the Earth moon. (Jupiter itself would be much larger still).
- btilly 2y agoA planet formed out of an accretion disk is generally a planet under continued bombardment from further accretion. The only exception that we know of is our own Solar System. Where Jupiter acts like a vacuum cleaner to reduce material that might hit Earth. We knkw of no other system with both Earth-like planets and gas giants. Given how catastrophic the remaining asteroids have been for us (bye bye dinosaurs), this is unlikely to be a coincidence. Unless we find a similar arrangement around a white dwarf, the time spent in the habitable zone isn't the only important factor for stability over evolutionary time frames.
- aw1621107 2y ago> The only exception that we know of is our own Solar System. Where Jupiter acts like a vacuum cleaner to reduce material that might hit Earth. We knkw of no other system with both Earth-like planets and gas giants. Isn't this a current limitation of our exoplanetary detection capabilities rather than something we know about other star systems in general? IIRC exoplanets are most easily discovered by the effect they have on their parent star's brightness when transiting it and/or due to causing the parent star to "wobble". Both those methods would tend to favor finding close and massive planets without necessarily ruling out smaller/more distant ones. Have exoplanet detection methods improved since I last read about them?
- Anarch157a 2y agoA large enough telescope in space, with a coronagraph could, in teory, find such planets by direct imaging. Right now, I believe only JWST fits the bill, but using it for this purpose would interfere with other types of research, so the coronagraph us used only only to observe planets the wer already discovered by other methods.
- cruffle_duffle 2y agoI’m pretty sure that new telescope being constructed in Chile will be large enough to directly image planets but I could be wrong.
- bookofjoe 2y ago"Dragon's Egg" by Robert L. Forward, published in 1980, is a hard sci-fi novel about intelligent life forms living on a neutron star. It's superb.
- FredPret 2y agoThat book is wonderful
- rokkamokka 2y agoOne of my favorite hard sci-fi books! Well worth a read
- danielbln 2y agoDoes it still hold up, technology prediction wise?
- Sharlin 2y agoIt doesn’t really concern itself with human technology. Yes, there are humans, and a human spaceship, but their role is secondary at best.
- jamiek88 2y agoit’s not really that kind of book. It’s more physics than tech. Highly recommend to a certain type of person. Many of whom frequent this message board !
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- divbzero 2y agoOne of my favorites too and immediately came to mind when I saw OP. I recommend the book highly if the subject matter of this thread interests you.
- cbzbc 2y ago
- mrangle 2y agoI'd never seek to deprive anyone of entertaining alien-life theories, but in general people wildly underestimate the factors that play into making Earth habitable. The only evidence for a habitable planet-type is the very precise conditions that comprise this one. Worse, it's unclear as to how much those conditions rely on the complete configuration of the greater solar system.
- iamgopal 2y agoWhile your argument is true, I would guess aliens will be quite a lot different than anything we know on this earth. Even different in so called life and death cycles, or even in the very definition of what we can call alive and dead. We should much broaden our search scope.
- zdragnar 2y agoWater is practically a miracle in itself. Reasonable range between freezing and boiling, simple structure, polar solvent and non-flammable. The hydrogen bonds allow lots of interesting processes, and it gets used in many many foundational biological functions as hydroxyl groups. The chemistry of such a simple molecule is difficult if not impossible to replace, and if you have it, the processes that we are familiar with are already efficient enough that there wouldn't be an advantage to not using them. Is it possibly there are configurations of life, such as not using either DNA or RNA? Sure. Is it likely that we wouldn't recognize that it is life? I doubt it very much. Aside from virii which likely devolved from living things rather than forming along side them, it's not hard to make a distinction at all.
- pockmarked19 2y agoIt’s also magnetic, making MRIs (and floating frogs) possible.
- mrangle 2y agoForgetting that we just leapt over the fact that the conditions of this planet are the only-evidence for the genesis of Life, and went straight to evolution, and while you logic is sound in theory, I'd again point to the probable fact that the necessary conditions for Life are massively underestimated. Perhaps mostly in terms of genesis, but also sustainability and even given theoretical evolutionary differences for hypothetical aliens. But genesis is really the only discussion that matters. Which is also very true for those that believe that there is a good possibility for alien Life. The math is beyond me to do, but I once got into a conversation with Claude that sought to find the probable distance of the nearest exoplanet that has possible Earth like conditions matching only a couple of additional factors that aren't commonly considered. Whereas I have dozens more. Claude's estimation was that the nearest such planet would be over two million light years away. Another conversation sought to understand the probability of an exact replica of this solar system somewhere else in the Universe. That probability is zero.
- devmap 2y agoDepends how big his cory is
- jmclnx 2y agoNice read! FWIW, I built a system the other day, its name, "whitedwf" :)
- idunnoman1222 2y agoThe end stage of stellar evolution cannot have life around it. There’s not enough water beyond the frost line to renew any planet around a white dwarf.
- credit_guy 2y agoHere's a (not completely flippant) answer: yes. At least in the case of Sirius B, and let's be hones, this is the case we care about, a planet that orbits it would be very close to Sirius A too. The distance between Sirius A and Sirius B is always between about 8 AU and 32 AU (1 AU = Sun-Earth distance). Since Sirius A is about 25 times more luminous than the Sun and Sirius B about 50 times dimmer, it is very likely that a planet orbiting Sirius B will receive most of its light/heat from Sirius A, and it would be somewhat comparable to what the Earth and Mars receive from the Sun.
- cyberax 2y agoOne unclear point: how would these planets form? Stars go through the red giant phase before becoming white dwarves, so they will swallow all the planets close to the star. And blow away any remnants of the accretion disk.
- science4sail 2y agoMaybe the white dwarf captures a rogue planet? The planet doesn't need to be from the star's original accretion disk.
- cyberax 2y agoYou can't capture a body with only a two-body interaction. You need at least 3 bodies for that. I guess a star with a Jupiter-class planet that survived the red giant phase might qualify. But then the conditions will have to be just right for the captured planet to end up near the star.
- unsupp0rted 2y agoWhite dwarfs have a surface, with 50km of crust. And they cool. They have a hydrogen atmosphere. Life doesn’t take very long to appear, perhaps just a few million years. We keep revising the number down on earth. It’s possible, and perhaps even likely, that most white dwarfs host life at some point in their lifecycle, when they’re cool enough.
- School-Cotton 2y agoMeanwhile on the HN-equivalent on some planet around a white dwarf: “can life emerge around a yellow star?”
- pavel_lishin 2y ago"No way! Those things shoot out flares, and any planet would have to be so far out from the star that it wouldn't be tidally locked; between the wild swings in temperature on a daily basis and the fact that the literal lithosphere is constantly swirling around under you, there's approximately zero chance that life could evolve there, and even if it did, even less chance for it to survive long enough to achieve anything interesting."
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- metalman 2y agosuedo - science and less fun than speculating about Gods preferenc in tooth care, paste or powder? Everyone agrees, right!, that we need a several orders of magnitude greater power space based telescope, solely devoted to examining extra solar planets,and then just see what is there. No matter what, it will be very interesting,and generate data usefull in many lines of study. That, or there is an astronomicaly slim chance we will get lucky and someone out there is broadcasting on a frequency that we are look8ng at. Starship changes the equasion, and its time to get the job, done.Now. Think about it, the whole world will drop tools and watch, everytime a new planet comes into focus. Way better than what we are watching now, and will cost, a whole lot less. tick twitch mega goog tube, blarg!