[HN Gopher] We've spotted a planet surviving its dying star
___________________________________________________________________
We've spotted a planet surviving its dying star
Author : gmays
Score : 159 points
Date : 2021-10-14 12:08 UTC (1 days ago)
(HTM) web link (theconversation.com)
(TXT) w3m dump (theconversation.com)
| eesmith wrote:
| Published at https://www.nature.com/articles/s41586-021-03869-6 .
| "Dying" refers to "survive the volatile evolution of their host
| stars into white dwarfs."
| TMWNN wrote:
| The classic short story "A Pail of Air" (1951;
| <https://en.wikipedia.org/wiki/A_Pail_of_Air>) depicts human
| survivors of a frozen Earth without the Sun.
| denton-scratch wrote:
| "Dying" is a bit of an under-statement. A white dwarf is to all
| intents and purposes dead. It has no source of energy, and
| radiates only because of stored heat.
|
| That heat dissipates so slowly that (AIUI) no white dwarf in the
| universe has yet had time to cool down enough to stop radiating
| (i.e. the universe does not yet contain any black dwarves).
|
| So a star that is in the process of collapsing into a white dwarf
| could reasonably be said to be "dying". Once it's collapsed, it's
| dead.
| Voloskaya wrote:
| "Dying" is not referring to the state of the star today, but to
| the process of death: the planet survived while it's star was
| dying, which is the interesting bit of the story.
| denton-scratch wrote:
| Agreed.
|
| To survive in orbit around a WD is not a remarkable
| achievement - you just carry on orbiting forever (roughly).
| Orbiting a red giant would be pretty interesting, though -
| the RG has an indistinct surface, its diameter and luminosity
| varies, and it emits a lot of material as wind.
|
| To survive in orbit around a neutron star would be another
| thing again. Neutron stars have intense magnetic fields, and
| spin rather quickly, resulting in a rotating field that is
| wrapped around on itself. That in effect creates a particle
| accelerator, driving electron flows (the electrons were all
| expelled when the NS collapsed) with extreme energies.
|
| Short of hanging around near an exploding supernova, I can't
| imagine a more hostile environment.
| hinkley wrote:
| Would the magnetic fields of a neutron star create a tidal
| locking effect through eddy currents in the planet's core,
| boosting it into a larger orbit and slowing the spin of the
| star? Seems like a giant inside out induction motor.
|
| I wonder what the band of survival is, where the planet
| doesn't get turned to Swiss cheese first.
| denton-scratch wrote:
| I have no idea what the neighbourhood of a neutron star
| is like, nor what the effects of such intense fields
| might be. This is theoretical physics and cosmology. I'm
| not competent even to speculate.
|
| Yes, I get the "induction motor" idea. With fields and
| voltages that intense, I guess just about anything
| becomes conductive.
|
| [Edit] I don't know whether those field strengths are
| consistent with atoms continuing to be atoms - I guess
| there must be some range beyond which a thing like a
| planet could maintain its integrity. But (guessing
| wildly) I would expect there to be a region around a
| neutron star within which it is impossible for atoms to
| exist.
| justshowpost wrote:
| Newly discovered Click-Bayitt type stars
| [deleted]
| postalrat wrote:
| Next you are going to say that a phone is dead unless it's
| being charged.
| denton-scratch wrote:
| Please explain how a "charger" for a white dwarf might work!
| I mean, you could just chuck a huge ball of hydrogen at it;
| that might work, but it'd be easier to just bundle together
| two balls of hydrogen and make a new star.
|
| I think I'd expect a charger to restore a phone to something
| like its as-new functionality. I've never heard of any
| mechanism that could change a white dwarf into not a white
| dwarf, other than extreme age, or being merged with another
| object.
| rapsey wrote:
| How would we see black dwarves?
| Chris2048 wrote:
| A BD is still hotter than background temp, so you could maybe
| see faint IR, and you could initially find it as a result of
| its mass if there are nearby objects orbiting (although now
| less illuminated), or simply transitioning in front of other
| stars (I guess that's how they find wandering planets?).
|
| Alternatively, map all the white dwarves, then wait long
| enough, then look again..
| kadoban wrote:
| You'd probably also be able to see white dwarves that were
| on their way to being black (whatever the threshold is).
| Chris2048 wrote:
| Given there are no BDs (so they are theoretical) maybe
| there isn't a threshold defined?
|
| A WD will slowly cool to a BD over Trillions of years, so
| it's all linear. Funnily enough, they are probably every
| shade of red/brown in-between - but "brown dwarves" are
| usually reserved for objects that never where "proper"
| hydrogen-fusing stars, but are large enough to fuse
| deuterium.
| kijin wrote:
| There's no hard threshold, the star just fades gradually
| from #FFF to #000.
|
| A fully black dwarf would be so cold it would be
| indistinguishable from cosmic background radiation, but
| that's going to take at least a trillion times longer
| than the current age of the universe. Not just slightly
| longer.
| kadoban wrote:
| Right. I'm just saying that if the are any black dwarfs
| (which there should not be), we should be able to find
| ~arbitrarily dim ones as well, down to our ability to
| see.
| dredmorbius wrote:
| Gravitational lensing, most likely.
|
| Possibly through gravitational interactions with non-dwarf
| stars in the same system.
|
| There not being any yet makes either method somewhat more
| challenging.
| Ericson2314 wrote:
| If there were bright things behind them
|
| The universe is young, a lot of stuff hasn't happened yet. It
| wouldn't be surprising if we are about the earliest life of
| this sort that could exist.
| vlovich123 wrote:
| I thought the cosmological expansion theory of the standard
| model was falling apart calling into question the Big Bang
| theory. If that's the case, then are we sure we have a good
| handle on the age of the universe?
| garblegarble wrote:
| Do you have any links where I can read more about that?
| That's fascinating and I wasn't aware, and I evidently am
| not using the right search terms to find out more
| Taek wrote:
| Maybe unrelated but YouTube has been throwing a lot of
| faux science and astronomy at me lately. Youtubers
| reading controversial papers presented as indisputable
| even when there's no scientific consensus at all on the
| results.
| whatshisface wrote:
| It's depressing to think about, but for many intents and
| purposes fake space facts are just as good as true space
| facts.
| 6502nerdface wrote:
| Especially for purposes of monetizing YouTube videos.
| contravariant wrote:
| Depends on your perspective I suppose. Most of the stars
| have already formed and star formation will slowly grind to
| a halt in a few billion years.
| Ericson2314 wrote:
| old and young universe then :)
|
| At least, I can understand visualize the time scale of
| the universe a lot better than I can visual the length
| scale. Speed of light doesn't feel like 1/1 to humans!
| JohnJamesRambo wrote:
| https://www.scientificamerican.com/article/living-near-a-whi...
|
| I've always found this idea neat.
| Koshkin wrote:
| An informative piece, thanks for sharing. (Being tidally
| locked complicates the situation, I think.)
| uyaij wrote:
| > By damping trash onto the surface of the white dwarf, one
| could harvest its gravitational binding energy from the
| emitted electromagnetic radiation at nearly the yield of
| nuclear fuel.
|
| This sounds interesting, how would such a method of power
| generation work?
| jerf wrote:
| Well, that very nearly _is_ the method of power generation.
| It would presumably be paired with some sort of Dyson
| sphere around the white dwarf. (Remember that a "Dyson
| sphere" isn't necessarily a solid shell, but just some
| configuration of matter where no matter which direction the
| energy goes it is intercepted by something.)
|
| You may also enjoy: https://www.youtube.com/watch?v=t-O-
| Qdh7VvQ which is a minutephysics on black hole power using
| much the same principles but attaining yet higher
| efficiencies.
| justshowpost wrote:
| Sorry, but it has to be rigid to be a sphere. Angular
| momentum is a bitch!
|
| PS: Dyson Spheres is misnomer, Olaf Stapledon should be
| credited for this idea (Star Maker 1937)
| FredPret wrote:
| So we would decelerate the trash, it hits the white
| dwarf, gets crushed, and then undergoes various nuclear
| transformations resulting in energy output we would then
| capture with our Dyson swarm?
| m1n1 wrote:
| Is "damping" a technical term, distinct from "dumping"? The
| article uses it more than once so it seems deliberate...
| orra wrote:
| Damping is a physics or maths term. To damp means to
| (steadily?) decrease the amplitude of a wave or
| oscillation.
| saltcured wrote:
| Damping is generally a technique which reduces, slows, or
| restricts a system. It is not a synonym for dumping. We
| have old, related terms like the "damper" on a fireplace,
| which I suspect may invoke a more basic analogy of
| putting water on wood fuel, i.e. making it damp and
| slower to burn.
|
| In modern usage, "damping" usually refers to a drag or
| parasitic affect in some oscillatory system, but it does
| not have to be oscillatory. It can be other drag effects
| that convert energy, with a usual assumption that it will
| bring the system to a new equilibrium. An object falling
| through the atmosphere can be considered to have its fall
| dampened by the air drag, converging towards its terminal
| velocity.
|
| I am not familiar with all the physics involved in
| falling towards/into such a star, so I do not know if
| there are field effects which would cause damping of the
| fall prior to impact of the trash with an actual surface,
| similar to the atmospheric descent towards earth. I also
| wonder if they imagine the orbital system is being damped
| to allow the trash to impact the star, by bleeding off
| tangential velocity to decay the orbit.
| tamaharbor wrote:
| I assume this would accelerate global warming.
| justshowpost wrote:
| Isn't that just a simple formula? I even seen planet
| destroyed/remains on some of stellar evolution simulators.
|
| It all depends on orbit radius and star mass at the end of
| Asymptotic Red Giant Branch.
|
| Note that white dwarves aren't stars but rather _stellar
| remnants_ without energy source.
| yummybear wrote:
| If you write an article with "we spotted", then please provide
| some image material, even if only a graph.
| purplecats wrote:
| It seems to be the cool thing to do lately. Especially if you
| have a visual web app, a tool that has a functional GUI
| component, or a breaking story about the planet or a new piece
| of hardware, you must make sure not to include the one thing
| that would make it most worthwhile -- a picture.
| [deleted]
| reedf1 wrote:
| You'd probably be disappointed. The best you could hope for is
| a graph of luminous flux vs time, showing the slightest
| decrease as the planet transits some emission nebulae.
| [deleted]
| nsonha wrote:
| Astronomy "images" are computer generated anyway, often with
| artistic touches.
| zhte415 wrote:
| While I'm no astrophysiyst I don't think it's a matter of
| 'their sun was there last week, look, this week it's not' and
| nor do I think an artist's impression of something orbiting
| nothing adds any more, nay, indeed adds nothing, to the written
| description.
| wongarsu wrote:
| The paper contains figures like [1] or [2], which I think do
| add something to the written description (and obviously the
| paper authors thought so too, otherwise they wouldn't have
| included it in the paper). These visuals are quite useful
| when talking about what we mean by "spotted" (though the
| context is important and the article only spends maybe two
| paragraphs on the actual observation method, so there's some
| danger of misinterpretation)
|
| 1: https://www.nature.com/articles/s41586-021-03869-6/figures
| /1...
|
| 2:
| https://www.nature.com/articles/s41586-021-03869-6/figures/7
| simonh wrote:
| Those images would be copyrighted, so may not be available
| to the publisher of the article.
| sigg3 wrote:
| Where are all the graphical artists at?
|
| We had an Ask HN here, like yesterday.
| wongarsu wrote:
| I'm sure the authors and their institutions would be
| happy to grant the right to use the images in an article
| about the paper if somebody asked them. Publicity for the
| finding is in their best interest. Unless their
| publishing agreement with Nature restricts this, not sure
| how strict exclusivity is in those cases
| simonh wrote:
| In some cases, for some papers it might be possible to
| eventually get rights to the charts that would satisfy
| your own publisher's legal department yes. They'd have to
| jump through those hoops every time though, and time is
| money.
| ziddoap wrote:
| Perhaps I missed it, but I'm curious to how they know this is a
| planet which survived the red giant phase vs. a planet which was
| captured afterwards (or formed from the debris caused from the
| star -> red giant -> white dwarf transition). Maybe it's covered
| more in actual paper.
| platz wrote:
| But, who wants to live forever?
| shadykiller wrote:
| Why would the planet be destroyed or have it's course altered ?
| The Star's mass remains the same and so does the gravity.
| Wouldn't the planet's own gravity hold it up when it's engulfed,
| and retrain shape when the star becomes a white dwarf ?
| joe-collins wrote:
| Well, there would be some extra drag, for one.
| MauranKilom wrote:
| > The Star's mass remains the same
|
| What makes you think so? I'm no expert, but matter is
| definitely expelled in the process of forming a white dwarf.
| The stuff scouring the inner planets doesn't appear out of thin
| air...
|
| This random paper also appears to say that the mass lost is on
| the order of half the initial mass:
|
| https://iopscience.iop.org/article/10.3847/1538-4357/aadfd6/...
|
| > total stellar mass loss ranges from 33% of M_initial at 0.83
| M_sun to 83% of M_initial at 7.5 M_sun.
| FredPret wrote:
| Not an astrophysicist, but it might get torched, blown away by
| the initial shockwave, or maybe drag between the planet and the
| solar atmosphere will slow its orbit into a collision course.
| tlholaday wrote:
| Sol is gas, right?
|
| Gasses cool when they expand, right?
|
| What's the expected surface temperature of Sol after it has
| expanded past Earth's orbit?
| gs17 wrote:
| Looks like it will drop to about half the current surface
| temperature as it expands (although this seems to be talking
| about it at around 0.5 AU) http://www.astronomy.ohio-
| state.edu/~ryden/ast162_4/notes15....
| tlholaday wrote:
| Thanks for the link. I wonder what temperature prevails at
| 1.0 AU.
|
| On the one hand, artists' conceptions of boiled oceans and
| cities in cinders that saddened and discouraged me in my
| childhood. On the other hand, the heat energy density of Sol
| today is comparable to a compost heap. When the radius of a
| sphere doubles, it's volume increase eight times.
|
| If Sol is too itsy to start helium fusion, maybe orbiting
| within the post-expansion photosphere - the hydrogen envelope
| - is chill, damp, and sparky?
| rootusrootus wrote:
| The sun won't (potentially) swallow up the Earth for about
| 8 billion more years. The carbon cycle on this planet will
| have ended about 7 billion years before then; the increased
| output of the sun will have boiled away the oceans; plate
| tectonics will stop, etc. There won't be anything alive on
| this planet left to see the sun burn out.
| edge17 wrote:
| Out of curiosity, the video part way down ("White Drwarf System
| Animation Text") showing the dying star... how are these videos
| created? Is it done in something like Blender? The video credits
| Keck Observatory, do they have 3d artists on staff for this kind
| of thing? Do Astronomy grad students just learn how to create
| visualizations? What's the turnaround for getting something like
| this made because I'm assuming it was made for the press release.
| Gauntleteer wrote:
| I work for the Keck Observatory (engineer). Far as I know we do
| not have any 3D animators on staff. We produce images from our
| science instruments for the astronomers to download and they
| all eventually end up here:
| https://www2.keck.hawaii.edu/koa/public/koa.php
| t789623239782 wrote:
| The first extrasolar planets discovered had survived a supernova
| explosion: https://en.wikipedia.org/wiki/PSR_B1257%2B12
___________________________________________________________________
(page generated 2021-10-15 23:01 UTC)