Can life emerge around a white dwarf?

https://www.centauri-dreams.org/2024/12/06/can-life-emerge-around-a-white-dwarf/

by JPLeRouzic • 2 years ago

147 98 2 years ago

A_D_E_P_T4• 2 years ago

Hmm. 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_fire2• 2 years ago

At 1/100 distance, wouldn't a hypothetical planet be tidally locked to the white dwarf?

Could tidally locked planets be suitable for life?

cenamus• 2 years ago

Not quite that close but Mercury seems to have an interesting interaction with the sun

https://en.m.wikipedia.org/wiki/Mercury_(planet)#Spin-orbit_...

A_D_E_P_T4• 2 years 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.

BurningFrog• 2 years ago

On 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!

rybosome• 2 years ago

I 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• 2 years ago

A 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• 2 years 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_T4• 2 years ago

Which has yet to be experimentally observed. At some point we'll be able to rule it out, I'm sure.

api4• 2 years ago

What 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• 2 years ago

Also 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.

pfdietz3• 2 years ago

Although rockets could take you between closely spaced planets, the delta V to escape the system would be much greater than in our solar system, by an order of magnitude. The habitable planet would be much deeper in the star's gravity well than we are in our Sun's.

Travel times between inner planets would be very short, I admit.

forgetfreeman• 2 years ago

Upvoted for "they probably look like crabs". I see what you did there and I am here for it.

russdill• 2 years ago

If it's super easy to get to orbit, it's also super easy for your atmosphere to get to orbit.

hermitcrab• 2 years ago

They probably look like crabs though.

It's crabs all the way down. https://en.wikipedia.org/wiki/Carcinisation

jajko• 2 years ago

Wouldn'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• 2 years ago

I 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_lishin2• 2 years 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.

0823498723498723• 2 years ago

compare Forward, Dragon's Egg (1980)

cheela• 2 years ago

For reference, https://mdpub.github.io/cheela

0823498723498723• 2 years ago

while we're at it*, RLF82: "Flattening spacetime near the Earth": https://journals.aps.org/prd/abstract/10.1103/PhysRevD.26.73...

* (and I am admiring the specificity of that HN acct)

thechao• 2 years ago

Or, more directly, Niven’s “The Smoke Ring” about humans living directly in an oxygenated accretion disk around a white dwarf.

ossopite• 2 years ago

I think you wrote compare forward as a long version of cf., but I believe cf. is actually short for the latin confer

0823498723498723• 2 years ago

Forward is the author :) 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.

pfdietz3• 2 years ago

The 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• 2 years ago

It'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• 2 years ago

A 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• 2 years 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?

Anarch157a2• 2 years ago

A 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_duffle3• 2 years ago

Both those methods would tend to favor finding close and massive planets without necessarily ruling out smaller/more distant ones.

They also favor ones whose orbit passes between us and their star, which dims the star and lets us see it. If the planet’s orbit doesn’t block the star, we’ll never know it was there using our current toolset.

I read somewhere that only like 2% of all planet’s have orbits that come between us and their star—which seems like a plausible figure to me, it’s a number you can probably derive from some simple math. This means until we find other ways to observe planets, we are only able to see a very small number of them out there.

Incidentally if other intelligent life is out there planet hunting using the same method of observing planets pass between the star and the observer, it means the odds of them finding earth are pretty small. They’d have to be positioned such that the earth comes between our sun and their line of sight.

bookofjoe• 2 years 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• 2 years ago

That book is wonderful

rokkamokka• 2 years ago

One of my favorite hard sci-fi books! Well worth a read

danielbln• 2 years ago

Does it still hold up, technology prediction wise?

divbzero• 2 years ago

One 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• 2 years ago

More recently, "Flux" by Stephen Baxter is about a engineered human analogues living on a neutron star.

bmitc2• 2 years ago

Have there ever been any further developments and investigations along these lines?

mrangle3• 2 years ago

I'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• 2 years ago

While 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.

zdragnar2• 2 years ago

Water 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.

mrangle3• 2 years ago

Forgetting 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.

firebot• 2 years ago

Right, this particular solar system happens to have a planet that peoples.

Yet the origins of life are elusive, and perhaps even multiple and relative, that the origins of life might just be a process the universe does countless times, independently. Or perhaps the seeds all started long ago, and life on this side of the universe is related to life on every side of it.

nox101• 2 years ago

Given that they've found living organisms in nuclear reactors and other extreme conditions it doesn't seem likely that "earth like conditions" are a requirement for life

zdragnar2• 2 years ago

There's a difference between life forms that can survive a particular environment, and all of the phases of incremental steps towards forming the first life in such an environment.

There's nothing to do but speculate until proven otherwise, since we don't actually know what those steps exactly are. My personal suspicion is that we are more likely to find life in earth like conditions than anywhere else, though.

mrangle3• 2 years ago

And yet nuclear reactors are on Earth. Again, people underestimate the factors involved. Have these organisms been shown to derive from an alien taxonomy?

bmitc2• 2 years ago

The universe is a big place, and we don't really possess the ability to find or see an Earth-like candidate as of yet. Our exoplanet searches are fairly rudimentary. For the solar system, it's very possible that at least two planets have had life and that even some moons may currently have it. Given that, it seems pretty unlikely that there isn't life elsewhere.

Given the right conditions, such as Earth, life isn't hard. It showed up almost immediately.

devmap• 2 years ago

Depends how big his cory is

jmclnx• 2 years ago

Nice read! FWIW, I built a system the other day, its name, "whitedwf" :)

idunnoman1222• 2 years ago

The 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• 2 years ago

Here'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.

cyberax2• 2 years ago

One 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• 2 years ago

Maybe the white dwarf captures a rogue planet? The planet doesn't need to be from the star's original accretion disk.

cyberax2• 2 years ago

You 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• 2 years ago

White 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.

umanwizard• 2 years ago

Meanwhile on the HN-equivalent on some planet around a white dwarf: “can life emerge around a yellow star?”

pavel_lishin2• 2 years 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."

metalman• 2 years ago

suedo - 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!

Can life emerge around a white dwarf?

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