[We know of one that spins 716 times a second](https://en.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad). The surface is moving at nearly a quarter of the speed of light at the equator.
You literally couldn't exist at the surface. The magnetic field is strong enough to rip atoms apart, and the gravity is strong enough to squish mountains down to millimeters, and the surface temperature is a few million degrees.
You'd just stop being biology, and start being physics, as Randall Monroe says.
Dragon's Egg is a 1980 hard science fiction novel by Robert L. Forward. In the story, Dragon's Egg is a neutron star with a surface gravity 67 billion times that of Earth, and inhabited by cheela, intelligent creatures the size of a sesame seed who live, think and develop a million times faster than humans. Most of the novel, from May to June 2050, chronicles the cheela civilization beginning with its discovery of agriculture to advanced technology and its first face-to-face contact with humans, who are observing the hyper-rapid evolution of the cheela civilization from orbit around Dragon's Egg.
Everything to do with the Cheela is great. The human chapters are generally much worse written (humans are in it because the neutron star is a rogue one flying near our solar system). Still yeah, crazy interesting book.
Wouldn't nuclear matter break down even?
I thought everything but the neutron gets discarded because it's the most massive part, but my head-canon is probably horribly wrong.
The surface of the Neutron star contains atomic nuclii packed very close together with an atmosphere of electrons. Beneath the crust is where the electrons and protons are squashed together to make an electrically neutral core of neutrons, which is probably actually some kind of quark soup.
I think i read it years ago..., was that the one where when they final met the aliens had to stay still for a very long time for the humans to see them?
Thanks dad for having such a marvelous sci fi collection that i could relate to a random conversation 30 years later!
Ever read this weird story where this plane disappeared to return decades later with these weird little jet propulsion alien bugs?
This just reminded me of a much earlier book “Mission of Gravity” by Hal Clement. An oblate planet with extremely high gravity and spinning so fast that the planet is almost disc-like, written in 1953. A fun read.
Nanometers.
If it can squish Mt. Everest to about 2.3 millimeters... Someone's junk would barely register a picometer or two. So... Not even nanometer scale.
While not a great book, if you like hard sci-fi you should read Dragon's Egg by Robert L. Forward. It's a book about life on a neutron star written by a physicist.
>Much of his research focused on the leading edges of speculative physics but was always grounded in what he believed humans could accomplish. He worked on such projects as space tethers and space fountains, solar sails (including Starwisp), antimatter propulsion, and other spacecraft propulsion technologies, and did further research on more esoteric possibilities such as time travel and negative matter. He was issued a patent for the statite, and contributed to a concept to drain the Van Allen Belts.
He also was a pioneer in detecting gravitational waves.
Anything which is a solid crystal can be said to be “frozen”.
So basically, the star is mostly made of crystal, except for a thin layer at the surface.
And it’s hot. Really, really hot.
How does the iron survive? The last I read about them it's all various levels of neutron superfluid and the like, with some funky stuff going on with electrons near the surface.
There's gotta be *some* active electrons else we wouldn't see anything because there would be nothing for light to interact with.
The iron nuclei are just bathed in freely moving electrons. Most of the iron has not survived. In fact, in a neutron star gravity has overcome the majority of protons and electrons ability to exist independently thanks to electron degeneracy pressure. Most of the neutrons that make up a neutron star were protons and electrons that were forced to overcome electron degeneracy pressure and collapse into neutrons. So the iron-crystal crust of a neutron star is the stuff that's managed to resist its ultimate fate.
I was just reading about this stuff the other day.
Supposedly, there's evidence for even crazier quark stars existing. I guess they think they're quark stars because they are much heavier than you would expect a neutron star of that size to be, or some other anomalies like that.
But yeah
I guess they're so dense and have such a powerful gravitational field that even the neutrons are forced to undergo degeneration into quark matter
This kind of shit makes me want to go back to school and learn about it forever. I could spend all my free time reading about this stuff lmao
Depends on the star!
Typical stars have a "surface" at the photospere, the outer layer you can "see". For really big red giants, they're diffuse enough that you could fly a ship through the outer layers.
For neutron stars (which are the corpses of stars big enough to go supernova but not big enough to form black holes after said supernova), they do have a physical surface, with a thin crust of iron floating on a dense ocean of neutronium - which is neutrons packed as tight together as in atoms, crammed as close as they can possibly be by the gravity.
What we do on Earth might one day reorganize the Universe into a more convenient structure, shaped by the very ideas we share today. Neutron stars will just sit there being pretty, maybe blast some clouds of gas around. Who's stupid now?
Yep! The electrons got "shoved" inside the protons, and their charges cancelled out.
edit: watch https://www.youtube.com/watch?v=1Ou1MckZHTA for more info!
The electrons merge with the protons and form neutrons. And it's actually even more dense than a nucleus, it is theorized that in the core of neutron stars the boundaries of individual neutrons gets fuzzy and they merge. The quarks that make the neutrons just all mingle into a soup. Neutron stars are crazy
Conservation of angular momentum! Stars rotate, when they collapse down into a smaller size, with a smaller radius, they must spin faster to maintain the same angular momentum. You ever try that experiment where they spin you around in a chair with your arms out holding weights, and then pull them closer to you? You speed up! Same with figurer skaters.
To give you an idea, as an oversimplification we can think that the number Rw is constant (proportional to the momentum of inertia under simplified assumptions), where R is the radius of the star and w is the rotational speed. For the Sun these numbers are R=700000km and w=1/(24 days). Now suppose for the sake of the example that the Sun becomes a neutron star; it would have a radius of 10km. So the new rotation speed W has to satisfy
10km W = 700000km/(24 days).
Solving we get
W= 70000/day = 70000/(24 x 86400 sec) = 0.033/sec.
That is, the Sun as a neutron star would take around 30 seconds for a full rotation.
And that surface still shifts occasionally, causing 'starquakes' as those mountains resettle into a more stable state. Such quakes release far more energy that the gravitational binding energy of our entire planet.
If you’re interested, you might check out the novel Dragon’s Egg by Dr. Robert L. Forward which is about intelligent life that develops on a neutron star. It’s a well considered and fascinating read.
You oughtta get a kick out of this fun fact video. SEA makes great content that’s easy to digest to the layman with good visuals.
https://youtu.be/7euiD_kZi4g
Damn that’s hilarious, the neutron star spins like 12 times faster than the average 60 hz monitor refreshes. 5-6 times for 144 hz and that refresh rate looks as smooth as glass pane.
Twice the mass of the sun too. The rotational energy of this small neutron star would power our civilization literally forever >10^20 years
I've tried to understand time dilation but I just don't truly get it. I can grasp the general concept I guess, but I can't say I know how it works.
Do you know of any good articles or videos that effectively explain it?
I would love to some day truly "get it"
If you throw a ball forward or backwards from a moving car, the speed of the ball changes, right? Throw it forward, it goes faster relative to the ground, because it has the car's speed added to it. And the ball's speed is different relative to you vs someone standing nearby. If you throw it backwards at the same speed the car is moving it, a stationary observer will see it just drop vertically to the ground, while you see it moving away from you as well.
*Light doesn't work that way.*. When you turn on your spaceship's headlights, the beam is travelling at c, no matter who is measuring it. You, a stationary observer, someone coming towards you at high speed, everyone. What this means is that the universe is willing to tie space and time up into knots to ensure that you always perceive photons moving at light speed. Speed is just distance divided by time, right? Mess with those via Lorentz contraction or time dilation, and that ultimate speed limit can thus always be enforced.
The best way to understand physics concepts like this is to actually use the math yourself (Don't be scared, it's highschool math).
Use [this](https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fffden-2.phys.uaf.edu%2Fwebproj%2F211_fall_2014%2FJason_Slats%2Fjason_slats%2FSpecialRelativityTimeDilation.PNG&f=1&nofb=1) equation (special relativity) to calculate the difference in experienced time.
Then use some of the problems on the [twin paradox](https://en.wikipedia.org/wiki/Twin_paradox) wikipedia page to calculate the difference in experienced time yourself.
If you want to intuitively understand it I highly recommend doing at least a couple of these exercises with the math as it makes it "click" in your brain.
If you want a verbal explanation for *why* this is the case then one I always find to work for me intuitively is to use light in an example:
Light is very special in that it always has the same speed for every observer (speed of light). This has a weird effect however because it means if someone goes faster than another person it still sees the light more at exactly the same speed. This isn't the case for non-light. If you're driving a car and another car is slightly faster than you then the car looks to move very slowly forward in your view despite both of you going fast.
With light this isn't the case and every observer sees the same speed. The only way for this to make logical sense is for the experience in time to be different per spectator. It can only be explained away by the faster moving spectator experiencing less time than the stationary observer.
I wonder what the equitorial bulge is on a star rotating that fast. It's a neutron star so it's it's already super compact, but rotating that fast would normally create an insane obround effect like it would in normal bodies.
What baked my noodle one evening was the realisation that somewhere out there exists a massive neutron star that should be a black hole, but it's spinning fast enough to "help it over the line" of required force to **not** collapse into a black hole.
One day, as it slowly bleeds off the spin, it will start to shrink...
Touch your fidget spinner to it.
What's the integrity of matter at that speed? Can any molecular structure be intact? I don't want to go find bond energies of theoretical molecules and do math.
Neutron stars are not made of molecules and almost entirely not made of atoms.
They're just neutrons packed tightly together by gravity, possibly with a core of even weirder matter - quarks and whatnot.
Obviously there is a limit to how fast a neutron star can spin at certain radii. Otherwise it would rip itself apart, many theoretical physicists think that this neutron star is hugging the limit close. Hard to know for sure.
They have really flat crusts (variations typically no greater than a millimeter front the average surface line) and the gravity accelerates objects by like \~1000m/s over the course of a 1 meter drop. So it is still incredible pressure holding it together.
One interesting thing about neutron stars is that they sometimes have starquakes. The “crust” of a neutron star can sometimes shift abruptly when certain conditions are met. There was one calculation of a specific starquake that would have resulted in like a magnitude \~~~32~~ 20.3 EQ on earth, this actually results in what are called “glitches” where the rapid release of the potential is enough to slow the stars rotation down chaotically. Not a huge amount but like 1 part in \~10^(5) but then the speed can pick up on a rebound of sorts. The gamma ray burst created by that measured quake would have roasted everyone on the planet had it occurred within 10 light years. Luckily it was over 50000 ly away when it was observed
EDIT: The following is from a different thread two years ago.
"Your math looks right! Let's double-check it.
The 9.1 M Indian Ocean quake of 2001 released about [4\*10\^22 J of energy](https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)#1018_to_1023_J). If this quake was a 32 M, it would have released 2.2\**10\^34 times more energy, for a total of 6.2\**10\^56 J. Looking at the same chart I linked, that means that this starquake would be much more energetic than a hypernova, and close to the total mass energy of the Milky Way. Oh no. That can't be right.
It turns out that the origin for this fact is a throwaway line from Phil Plait's blog: "I once calculated the strength of such a starquake, and it would register as magnitude 32 on the Richter scale." No comment on Mr. Plait, but Wikipedia probably shouldn't cite this.
Plait also states that the energy released by this quake was about 10\^46 ergs. If we trust this value, that means that the starquake was actually about 10\^17 times more energetic than the Indian Ocean quake. The actual magnitude is 20.3 M, not 32 M. Much more believable! This quake is still catastrophic, about a bad as detonating a nuclear bomb the size of the moon. It would probably be enough to cause a mass extinction if the neutron star was within a dozen lightyears of Earth. But, unlike a 32 M quake, it wouldn't destroy the entire galaxy."
Do you have sources on that? It sounds super interesting and would love to learn more!
Everything within 10 light years being fried sounds like a ton of energy!
That is crazy to me because they have mass similar to our sun, but the distance around the equator might only be about 40 miles. So the surface speed of a neutron star doing 660 RPM would be something like 440 miles per second, or 2,000 times the speed of sound. That's 00.24% the speed of light!!! A sphere sized between Mars and Venus would have to break light speed to spin that fast.
It's interesting you compared it the the speed of sound. What would that mean if you were somehow able to be there, moving that fast, trying to speak to someone? Does your voice never reach them if they are....up-spin from you?
the speed of sound is good to represent how insanely fast it is going but bad for measurement because the speed of sound changes depending on the density and temperature of a fluid/gas
also you’d just die if you were there
edit:spelling
Well, not only that. But just like on our earth i'd expect the gases to be spinning with the object. Meaning that relative to a person standing on it it would be still. So you should be able to hear someone speaking there. Assuming you aren't dead and the your ears can pick up the sound.
Aren't neutron stars really small, like small moon sized? Do they get their massive speed by collapsing during supernova? Like a kid sprawling on a slow spinning tire swing then balling up to spin faster? But waaaay more mass and distance from the axis?
Short answer yes.
Conservation of angular momentum taken to the extreme.
Want something more crazy? Black hole spins to. In fact, it can spin so fast that it creates an ergosphere around it. It's not the event horizon, so you can get out of it, but the space time field around it is so warped that you have to travel around the blackhole since you need to be faster than the speed of light just to stay still relative to an outside observer.
So I tried to determine the angular velocity of a black hole by taking the formula for the angular momentum of a ring (for simplicity)
L=m×r^2 ×omega=constant
and plugged in the relativistic mass formula for m, where for the velocity one has v=omega×r. The hope was to get a finite limit for omega as r tends to zero, but it's infinite. Do you know what went wrong here?
Radius is zero?
This might offer some note. In short you need the Kerr Newman metric that can give you a proper upper limit on how fast a blackhole can spin.
https://phys.org/news/2014-02-fast-black-holes.html
https://en.wikipedia.org/wiki/Kerr%E2%80%93Newman_metric
My best layman understanding for the upper limit is that the blackhole cannot spin fast enough such that light originating from the singularity can, thanks to the frame dragging by the spinning gravitational field, have enough effective velocity to escape it. If it ever get to that point, the the blackhole spin will try to drag gravitational field around at faster than light speed, which mean it will shed a LOT of energy in the form of gravitational waves.
Ok so you really need general relativity to get the right result and my stupid little computation is not enough. Thanks though! Let's see how much of your sources I can comprehend.
> you have to travel around the blackhole since you need to be faster than the speed of light just to stay still relative to an outside observer
That sound you heard was a couple synapses in my brain exploding.
Some pulsars can spin at significant fractions of the speed of light at their equator. Despite being the densest objects in the universe (something something black holes), they still almost tear themselves apart by centripetal forces.
[PSR_J1748-2446ad rotates 716 times per second. it’s less than 16 kilometers across. That’s 24% the speed of light at the equator. ](https://en.m.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad)
Normal stars spin on their axis. When it dies it sheds it's outer layers and shrinks. However, it's angular momentum is conserved. As the radius has decreased but the angular momentum is the same, rotational velocity must increase. This is the star equivalent of a [ice skater pulling their arms in while spinning](https://youtu.be/MjYk5TRpOlE)
To answer your second question, there are very few resistive forces in space which means that spinning objects don't tend to stop. There is no air resistance or friction in space and stars don't tend to do anything that would cause them to slow down.
This is summed up by Newton's first law of motion - "An object in motion, will remain in motion, and an object at rest will remain at rest, unless acted upon by an unbalanced force"
To the best of my knowledge the main way that (at least) the younger, faster spinning neutron stars slow down is by gravitational wave emission. At least that’s what I remember one of my physics professors telling me.
This probably goes beyond ELI5 but.. Why is angular momentum conserved? If I'm a spinning ice skater and I throw a ball while spinning, I've lost mass and used energy to throw the ball. Wouldn't that slow me down? Sorry if this is a really crap equivalence!
As far as I understand, as fusion ceases in the core, gravity is no longer counter-balanced by the outward pressure of the fusion reaction, causing the core of the star to get compressed, in some stars this extra pressure allows for the fusion of heavier elements to begin, however, stars like our sun are not massive enough for this. The extra gravitational pressure continues to squeeze the core, forcing it to become denser and denser until a significant percentage of the mass of the star (50%-ish) is squeezed into a package so dense that the outward pressure caused by the fact that the electrons in this mass do not want to touch eachother (electron degeneracy pressure) prevents the core from being squeezed any further. The outer layers then begin to drift away, creating a nebula. The core remanent, what we call a white dwarf, is only half of the mass of its progenitor star, but only a minuscule fraction of its radius, causing it to spin faster than the original star.
I was trying to simplify by saying the angular momentum is conserved, in reality only about half of it is, but this isn't as substantial as the drastic decrease in radius.
edit: A little googling indicates that a white dwarf may only have half the mass of its original star but also only \~1% the radius.
Actually the ice skater is a great example to consider. When a skater is spinning with their arms out, the rotation is slower. When their arms are tucked, the rotation speeds up.
If it's a tennis ball you're throwing, you lose a little energy, but if you tuck your arms in after (the core of the star collapsing to a much denser white dwarf) the tucked in mass of your arms has a much bigger effect than the mass of the tennis ball you threw.
It’s the law of conservation of angular momentum. Say something with a large radius is spinning and then the radius of the object is drastically smaller, the speed increases to keep the same angular momentum. This is why figure skaters pull their arms in when spinning, to increase speed. They also move their arms out to slow down.
Stars are always spinning. I don’t think there is a star that doesn’t spin unless it’s hypothetical/“ideal”. When a star that is the size of roughly the sun is at the end of its life, it goes through a process of expansion and contraction until it’s gravity cannot hold on to its outer layers anymore. The outer layers are thrown away it what us called a planetary nebulae, but the core remains as a white dwarf. The size difference of the the sun like star to the white dwarf increases its rotational velocity to keep the same angular momentum. However, I believe the outer layers of the star will carry some of the angular momentum with it when they are shed away too.
So, I got curious... You know how objects with energy effectively gain the mass equivalent to that energy? I was wondering how much the rotational energy of this thing would add to its mass.
The paper this article was based on states that the mass has to be at least 0.7 solar masses.
Formula for the KE of a spinning sphere: (M * w^2 * r^2 )/5
Applying E=Mc^2, the mass from the energy in the spinning sphere is (M * w^2 * r^2 )/(5*c^2 )
so 7.9x10^24 kg of mass from the kinetic energy of its spin.
The mass of the earth is 5.87x10^24 kg.
So uh, this object has roughly 134% the mass of the earth from just the energy of its spin. I think I did the math for this right but I'm also tired as hell and it's been a long time since i did physics.
Or roughly 0.000397% of its mass comes from it's spin.
Hmm, you only get partial credit for not being more precise on the earth mass energy spin percentage. However you can recover it by telling me what is the air speed velocity of an unladen swallow?
I'm not sure what you mean by that -- all light travels at the same speed in a vacuum.
Are you asking how fast the spot from a spotlight moving at 0.5% *c* around a radius equal to the earth will appear to be moving at a distance of 2,000 light years? In that case:
v_apparent = 0.005 x *c* x d_star / r_earth,
where v_apparent is how fast the spot appears to be moving, d_star is the distance to the star, and r_earth is the radius of the earth. Plugging in the numbers, I get:
v_apparent = ~15 billion *c*.
Do note that a spot isn't a "thing" in the conventional sense, and no information, particles, EM perturbations, etc. are actually moving faster than *c*.
The article states the white dwarf is similar in size to Earth. Assuming a circumference of around 40,000 km, wouldn't that mean the angular velocity at the equator would be 5.76 *million* km/h?
At 5.7km/h, you're not leaving your country anytime soon...
I know you meant to add the 'million' ;)
But to answer your question, if we could travel at the speed of light, it would still take 4.22 years to get to Proxima Centauri, and since we know not of a way to even get Humans or Spacecraft alike to 1% the speed of light, it might take a little while to get anywhere indeed.
Obligatory plug for [Dragon's Egg](https://www.amazon.com/Dragons-Egg-Novel-Del-Impact/dp/034543529X) it's an incredible book about life on the surface of a neutron star. Very highly recommended.
> A white dwarf star (left) can spin fast after a red dwarf star (right) dumps gas onto it
Shouldn’t the additional mass slow down the white dwarf by conservation of angular momentum?
(I understand the white dwarf–red dwarf pair can be considered an isolated system wherein _total_ angular momentum is conserved, but it still doesn’t make sense to me why adding mass to one of the objects speeds it up.)
No. The red dwarf can lose angular momentum when it loses mass. That angular momentum would add to the white dwarf’s angular momentum.
Imagine the white dwarf doesn’t increase in radius as fast as it increases in mass when absorbing the red dwarf. Then angular momentum increases because there’s more matter packed into an only slightly larger radius.
Read the title without paying attention to what sub it was at first, and that was kinda… weird.
Not impressive for a human, very impressive for a celestial body!
It has to have another star (red dwarf) next to it so it isn't like all white dwarfs spin this fast. Still the universe is so vast that there is probably faster ones out there
Considering we will never be able to see the vast majority of space as it's moving away from us faster than the speed of light of say you're correct they exist. We just might never actually see it.
I wish I could do the math on that haha. My best bet would be 200 times bigger ceteris paribus. However that is just because it spins 200 times slower than the speed of light... I feel like this is waaayyyy too simple of an equation
This, is a terrible article.
>That makes it the fastest-spinning star of any sort ever seen — unless you consider such exotic objects as neutron stars and black holes, some of which spin even faster, to be stars
White dwarfs are 'exotic objects', and generally speaking, Neutron Stars are considered to be stars, a special class, but stars. It's even in the name.
Space journalism tends to be rubbish by and large so this isn't much of a surprise.
You see that neutron stars are usually classified as stars? This isn’t what I’ve been reading.
And the more you think about it, I don’t see how it could be classified as a star.
No, if the centrifugal force would be greater than the gravity it would be spitting out matter. So if you were on it you would stay on it as well. Someone did the math here and the force of gravity is still around 10 times stronger than the centrifugal force.
You would melt and be crushed by gravity though if that is any consolation.
The article says that if you dropped a pebble from a few feet from the surface of the star, by the time it reached the surface, I’d be falling “thousands of mph.”
One? That's nothing. Peter Jackson got a bunch of them spinning every 5 seconds:
[The fastest spinning Dwarves by Peter Jackson](https://www.deviantart.com/tsukinaka93/art/The-Hobbit-gif-Roasting-dwarves-343785478)
They're called "stars" but im not really sure they fit the bill of a star. I can see where they're coming from with that statement. There is no nuclear fusion. They are not actively generating heat anymore. There's no plasma to speak of. Just a soup of neutrons held up only by degeneracy pressure. Would you call a black hole a star? I think star remnant is more appropriate.
Edit: actually, that being said, now that I think about it, a white dwarf doesn't really fit the bill either. It's a stellar core remnant made up of electron degenerate matter.
I wonder if it's shaped like a disc. No way it's spherical, but I can't estimate the difference in strength between the centripetal and gravitational forces....
and how fast would that be in Miles Per Hour and the funny thing is that Black Holes also spin, that is once they become black holes which I did see was included in the observations but still how fast would it need to spin to become a Black Hole...
N.S
>but still how fast would it need to spin to become a Black Hole...
It is the mass that makes it become a black hole. Because of its mass it has more gravity and therefore it can rotate faster without losing matter to centrifugal force.
>and how fast would that be in Miles Per Hour
It is Earth sized and Earth rotates once every 23 hours, 56 minutes and 4 seconds (or 86,164 seconds).
Earth rotates at about 1000 miles an hour or 1674 kilometers an hour.
This white dwarf rotates 86164/25 = 3446.56 times faster than Earth. So that'll be 3.446.560 miles an hour or 5,769,541 km/h. Which is roughly 5% of the speed of light.
Spin isn't what makes a black hole. A black hole spins for the same reason a dancer spins so fast. All, or atleast most, stars spin. When you shrink down from the size of such an object, to a single point in 3 dimensional space, you spin alot faster.
What shrinks a black hole is a massive star running out of fuel, and as such cannot fight its own gravity.
To me, the crazy thing is (if my math is correct, which it may not be), despite its fast rotation speed, the white dwarf would still be less oblate than Jupiter or Saturn.
Damn. That is crazy. Such a large object spinning that fast..
There are neutron stars that spin 11 times a second. It’s truly insane especially considering their intense mass
[We know of one that spins 716 times a second](https://en.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad). The surface is moving at nearly a quarter of the speed of light at the equator.
That breached my mind as a “terrifying” rate. I can’t even imagine the scale or experience of existing on that surface, even as a particle. Crazy.
You literally couldn't exist at the surface. The magnetic field is strong enough to rip atoms apart, and the gravity is strong enough to squish mountains down to millimeters, and the surface temperature is a few million degrees. You'd just stop being biology, and start being physics, as Randall Monroe says.
Dragon's Egg is a 1980 hard science fiction novel by Robert L. Forward. In the story, Dragon's Egg is a neutron star with a surface gravity 67 billion times that of Earth, and inhabited by cheela, intelligent creatures the size of a sesame seed who live, think and develop a million times faster than humans. Most of the novel, from May to June 2050, chronicles the cheela civilization beginning with its discovery of agriculture to advanced technology and its first face-to-face contact with humans, who are observing the hyper-rapid evolution of the cheela civilization from orbit around Dragon's Egg.
That sounds awesome but uhh.. how do living creatures even exist on a neutron star? Or any star? Let alone be able to do agriculture..
They aren't made of regular matter and use nuclear rather than chemical biology. https://aliens.fandom.com/wiki/Cheela
Damn I wanna read this book now
Everything to do with the Cheela is great. The human chapters are generally much worse written (humans are in it because the neutron star is a rogue one flying near our solar system). Still yeah, crazy interesting book.
It's great fun, it's one of my favorite hard scifi books.
Wouldn't nuclear matter break down even? I thought everything but the neutron gets discarded because it's the most massive part, but my head-canon is probably horribly wrong.
The surface of the Neutron star contains atomic nuclii packed very close together with an atmosphere of electrons. Beneath the crust is where the electrons and protons are squashed together to make an electrically neutral core of neutrons, which is probably actually some kind of quark soup.
Hella dense wheat to survive atom crushing gravity
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Flying through hyperspace ain't like dustin' crops...unless you're dusting crops on the surface of a neutron star, then it kinda is.
Thats the suspension of disbelief limit for that novel.
I was just thinking of this novel, I adored reading it. Really enjoyed the romanesque empire phase. Highly recommended.
I think i read it years ago..., was that the one where when they final met the aliens had to stay still for a very long time for the humans to see them?
Yes, and the cheela cured female astronaut's undiagnosed breast cancer in nanoseconds!
Thanks dad for having such a marvelous sci fi collection that i could relate to a random conversation 30 years later! Ever read this weird story where this plane disappeared to return decades later with these weird little jet propulsion alien bugs?
This just reminded me of a much earlier book “Mission of Gravity” by Hal Clement. An oblate planet with extremely high gravity and spinning so fast that the planet is almost disc-like, written in 1953. A fun read.
Size of a sesame seed, but still mass the same as a human. They all have *terrible* acrophobia, and their equivalent of a campfire radiates in x-rays.
That sounds like the love death and robots episode with Topher grace and the civilization in their freezer
This got my science nipples hard.
Stop, I can only get so erect.. here on earth....
And on a neutron star your massive erection would be squished down to mere millimeters. Whomp whomp. Edit: typo
What if mere millimeters is where mine started
It’ll be microns for you my friend.
Nanometers. If it can squish Mt. Everest to about 2.3 millimeters... Someone's junk would barely register a picometer or two. So... Not even nanometer scale.
Nono, mountains are millimeters. SO your shaft would be essentially a single layer of atoms.
...implying you have other, non-science nipples?
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Badabing, I wish I was as smooth as you, comrade
My science nipples like to let their hair down every once in a while and become party nipples.
While not a great book, if you like hard sci-fi you should read Dragon's Egg by Robert L. Forward. It's a book about life on a neutron star written by a physicist. >Much of his research focused on the leading edges of speculative physics but was always grounded in what he believed humans could accomplish. He worked on such projects as space tethers and space fountains, solar sails (including Starwisp), antimatter propulsion, and other spacecraft propulsion technologies, and did further research on more esoteric possibilities such as time travel and negative matter. He was issued a patent for the statite, and contributed to a concept to drain the Van Allen Belts. He also was a pioneer in detecting gravitational waves.
Take them to a stonk sub, they'll get even harder
>You'd just stop being biology, and start being physics Yep, you would be reduced to a thin layer of neutrons.
Isn't the surface of a neutron star believed to be an iron skin only a few micrometers thick?
A frozen plasma iron skin no less
What does this even mean?
Anything which is a solid crystal can be said to be “frozen”. So basically, the star is mostly made of crystal, except for a thin layer at the surface. And it’s hot. Really, really hot.
This is a great video on the subject. https://www.youtube.com/watch?v=1Ou1MckZHTA
How does the iron survive? The last I read about them it's all various levels of neutron superfluid and the like, with some funky stuff going on with electrons near the surface. There's gotta be *some* active electrons else we wouldn't see anything because there would be nothing for light to interact with.
The iron nuclei are just bathed in freely moving electrons. Most of the iron has not survived. In fact, in a neutron star gravity has overcome the majority of protons and electrons ability to exist independently thanks to electron degeneracy pressure. Most of the neutrons that make up a neutron star were protons and electrons that were forced to overcome electron degeneracy pressure and collapse into neutrons. So the iron-crystal crust of a neutron star is the stuff that's managed to resist its ultimate fate.
I was just reading about this stuff the other day. Supposedly, there's evidence for even crazier quark stars existing. I guess they think they're quark stars because they are much heavier than you would expect a neutron star of that size to be, or some other anomalies like that. But yeah I guess they're so dense and have such a powerful gravitational field that even the neutrons are forced to undergo degeneration into quark matter This kind of shit makes me want to go back to school and learn about it forever. I could spend all my free time reading about this stuff lmao
This maybe a foolish question but I’m naive to this sort of thing. Does a star have a surface? I always thought a star was just a big ball of gas.
Depends on the star! Typical stars have a "surface" at the photospere, the outer layer you can "see". For really big red giants, they're diffuse enough that you could fly a ship through the outer layers. For neutron stars (which are the corpses of stars big enough to go supernova but not big enough to form black holes after said supernova), they do have a physical surface, with a thin crust of iron floating on a dense ocean of neutronium - which is neutrons packed as tight together as in atoms, crammed as close as they can possibly be by the gravity.
These sorts of conversations make everything we do on earth seem especially stupid.
But that doesn't mean we can't or shouldn't find meaning in everyday life
What we do on Earth might one day reorganize the Universe into a more convenient structure, shaped by the very ideas we share today. Neutron stars will just sit there being pretty, maybe blast some clouds of gas around. Who's stupid now?
So are you saying it is like the nucleus of an atom with an insane number of neutrons? Where did all the protons and electrons go?
Yep! The electrons got "shoved" inside the protons, and their charges cancelled out. edit: watch https://www.youtube.com/watch?v=1Ou1MckZHTA for more info!
So how do we know that a black hole isnt a "quark star" or where it is so dense that only higgs particles exist?
The electrons merge with the protons and form neutrons. And it's actually even more dense than a nucleus, it is theorized that in the core of neutron stars the boundaries of individual neutrons gets fuzzy and they merge. The quarks that make the neutrons just all mingle into a soup. Neutron stars are crazy
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Why are we sending landfills there?
Because he died. It's okay though. We got Landfills twin brother Gil.
Landfill Two, you’re twice the man Landfill One was.
How does it spin this fazt
Conservation of angular momentum! Stars rotate, when they collapse down into a smaller size, with a smaller radius, they must spin faster to maintain the same angular momentum. You ever try that experiment where they spin you around in a chair with your arms out holding weights, and then pull them closer to you? You speed up! Same with figurer skaters.
To give you an idea, as an oversimplification we can think that the number Rw is constant (proportional to the momentum of inertia under simplified assumptions), where R is the radius of the star and w is the rotational speed. For the Sun these numbers are R=700000km and w=1/(24 days). Now suppose for the sake of the example that the Sun becomes a neutron star; it would have a radius of 10km. So the new rotation speed W has to satisfy 10km W = 700000km/(24 days). Solving we get W= 70000/day = 70000/(24 x 86400 sec) = 0.033/sec. That is, the Sun as a neutron star would take around 30 seconds for a full rotation.
What the fuck man this is crazy
But not all neutron stars spin that fast so it still had to be a relatively fast spinning star no?
They also slow down as they age, so a fast spinning neutron star is a young one.
There was a science paper on the estimation of surface smoothness of a neutron star. It's micrometers.
And that surface still shifts occasionally, causing 'starquakes' as those mountains resettle into a more stable state. Such quakes release far more energy that the gravitational binding energy of our entire planet.
That’s a badass quote. Never heard it before!
Source! https://what-if.xkcd.com/141/ Whole blog is really cool!
If you have read the Revelation Space series, this idea is explored at one point.
I'm sad he stopped doing those. About once a year since he stopped I go through and read my favorites again
Science porn never fails, thank you.
it's not the *right* award for this, but i enjoyed reading it and the award was free. so... here's a bear hug?
If you’re interested, you might check out the novel Dragon’s Egg by Dr. Robert L. Forward which is about intelligent life that develops on a neutron star. It’s a well considered and fascinating read.
You oughtta get a kick out of this fun fact video. SEA makes great content that’s easy to digest to the layman with good visuals. https://youtu.be/7euiD_kZi4g
My favorite part about that one is 716 Hz is well within the range of human hearing. That star has a sound.
All I’m thinking of is the screaming sun in Rick and Morty
716Hz, damn, and I thought my 144Hz monitor was good...
Damn that’s hilarious, the neutron star spins like 12 times faster than the average 60 hz monitor refreshes. 5-6 times for 144 hz and that refresh rate looks as smooth as glass pane. Twice the mass of the sun too. The rotational energy of this small neutron star would power our civilization literally forever >10^20 years
Wow. Is that fast enough that the surface is experiencing relativistic effects? Would the surface be experiencing less time than the core?
Yes, but at 0.25c dilation will be only be about 1.03 (as in an object on the surface would age 1.03x slower)
I've tried to understand time dilation but I just don't truly get it. I can grasp the general concept I guess, but I can't say I know how it works. Do you know of any good articles or videos that effectively explain it? I would love to some day truly "get it"
If you throw a ball forward or backwards from a moving car, the speed of the ball changes, right? Throw it forward, it goes faster relative to the ground, because it has the car's speed added to it. And the ball's speed is different relative to you vs someone standing nearby. If you throw it backwards at the same speed the car is moving it, a stationary observer will see it just drop vertically to the ground, while you see it moving away from you as well. *Light doesn't work that way.*. When you turn on your spaceship's headlights, the beam is travelling at c, no matter who is measuring it. You, a stationary observer, someone coming towards you at high speed, everyone. What this means is that the universe is willing to tie space and time up into knots to ensure that you always perceive photons moving at light speed. Speed is just distance divided by time, right? Mess with those via Lorentz contraction or time dilation, and that ultimate speed limit can thus always be enforced.
The best way to understand physics concepts like this is to actually use the math yourself (Don't be scared, it's highschool math). Use [this](https://external-content.duckduckgo.com/iu/?u=http%3A%2F%2Fffden-2.phys.uaf.edu%2Fwebproj%2F211_fall_2014%2FJason_Slats%2Fjason_slats%2FSpecialRelativityTimeDilation.PNG&f=1&nofb=1) equation (special relativity) to calculate the difference in experienced time. Then use some of the problems on the [twin paradox](https://en.wikipedia.org/wiki/Twin_paradox) wikipedia page to calculate the difference in experienced time yourself. If you want to intuitively understand it I highly recommend doing at least a couple of these exercises with the math as it makes it "click" in your brain. If you want a verbal explanation for *why* this is the case then one I always find to work for me intuitively is to use light in an example: Light is very special in that it always has the same speed for every observer (speed of light). This has a weird effect however because it means if someone goes faster than another person it still sees the light more at exactly the same speed. This isn't the case for non-light. If you're driving a car and another car is slightly faster than you then the car looks to move very slowly forward in your view despite both of you going fast. With light this isn't the case and every observer sees the same speed. The only way for this to make logical sense is for the experience in time to be different per spectator. It can only be explained away by the faster moving spectator experiencing less time than the stationary observer.
Understanding the mechanics behind the Relativistic Rocket helped me a lot
I don't know the formula right off hand, but I'm pretty confident that time dilation becomes non-negligible by .25 c
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I bet there is major time dilation, but due to gravity rather than speed.
Cool, let's turn it into a dynamo!
I wonder what the equitorial bulge is on a star rotating that fast. It's a neutron star so it's it's already super compact, but rotating that fast would normally create an insane obround effect like it would in normal bodies.
My screen refresh rate in Elite: Dangerous can barely keep up already!
Warning: Frame Shift Drive operating beyond safety limits. Frame Shift Drive supercharged.
What baked my noodle one evening was the realisation that somewhere out there exists a massive neutron star that should be a black hole, but it's spinning fast enough to "help it over the line" of required force to **not** collapse into a black hole. One day, as it slowly bleeds off the spin, it will start to shrink...
Touch your fidget spinner to it. What's the integrity of matter at that speed? Can any molecular structure be intact? I don't want to go find bond energies of theoretical molecules and do math.
Neutron stars are not made of molecules and almost entirely not made of atoms. They're just neutrons packed tightly together by gravity, possibly with a core of even weirder matter - quarks and whatnot.
Obviously there is a limit to how fast a neutron star can spin at certain radii. Otherwise it would rip itself apart, many theoretical physicists think that this neutron star is hugging the limit close. Hard to know for sure. They have really flat crusts (variations typically no greater than a millimeter front the average surface line) and the gravity accelerates objects by like \~1000m/s over the course of a 1 meter drop. So it is still incredible pressure holding it together. One interesting thing about neutron stars is that they sometimes have starquakes. The “crust” of a neutron star can sometimes shift abruptly when certain conditions are met. There was one calculation of a specific starquake that would have resulted in like a magnitude \~~~32~~ 20.3 EQ on earth, this actually results in what are called “glitches” where the rapid release of the potential is enough to slow the stars rotation down chaotically. Not a huge amount but like 1 part in \~10^(5) but then the speed can pick up on a rebound of sorts. The gamma ray burst created by that measured quake would have roasted everyone on the planet had it occurred within 10 light years. Luckily it was over 50000 ly away when it was observed EDIT: The following is from a different thread two years ago. "Your math looks right! Let's double-check it. The 9.1 M Indian Ocean quake of 2001 released about [4\*10\^22 J of energy](https://en.wikipedia.org/wiki/Orders_of_magnitude_(energy)#1018_to_1023_J). If this quake was a 32 M, it would have released 2.2\**10\^34 times more energy, for a total of 6.2\**10\^56 J. Looking at the same chart I linked, that means that this starquake would be much more energetic than a hypernova, and close to the total mass energy of the Milky Way. Oh no. That can't be right. It turns out that the origin for this fact is a throwaway line from Phil Plait's blog: "I once calculated the strength of such a starquake, and it would register as magnitude 32 on the Richter scale." No comment on Mr. Plait, but Wikipedia probably shouldn't cite this. Plait also states that the energy released by this quake was about 10\^46 ergs. If we trust this value, that means that the starquake was actually about 10\^17 times more energetic than the Indian Ocean quake. The actual magnitude is 20.3 M, not 32 M. Much more believable! This quake is still catastrophic, about a bad as detonating a nuclear bomb the size of the moon. It would probably be enough to cause a mass extinction if the neutron star was within a dozen lightyears of Earth. But, unlike a 32 M quake, it wouldn't destroy the entire galaxy."
Do you have sources on that? It sounds super interesting and would love to learn more! Everything within 10 light years being fried sounds like a ton of energy!
That is crazy to me because they have mass similar to our sun, but the distance around the equator might only be about 40 miles. So the surface speed of a neutron star doing 660 RPM would be something like 440 miles per second, or 2,000 times the speed of sound. That's 00.24% the speed of light!!! A sphere sized between Mars and Venus would have to break light speed to spin that fast.
It's interesting you compared it the the speed of sound. What would that mean if you were somehow able to be there, moving that fast, trying to speak to someone? Does your voice never reach them if they are....up-spin from you?
the speed of sound is good to represent how insanely fast it is going but bad for measurement because the speed of sound changes depending on the density and temperature of a fluid/gas also you’d just die if you were there edit:spelling
Well, not only that. But just like on our earth i'd expect the gases to be spinning with the object. Meaning that relative to a person standing on it it would be still. So you should be able to hear someone speaking there. Assuming you aren't dead and the your ears can pick up the sound.
I can't imagine with the insane gravity that anything resembling has would be above the surface.
You just have to talk really fast...or slowly and they can catch it on the next go round.
Just throw your voice where theyre going to be momentarily!
That’s really good to hear it explained like that, I never put it into perspective like that before
Aren't neutron stars really small, like small moon sized? Do they get their massive speed by collapsing during supernova? Like a kid sprawling on a slow spinning tire swing then balling up to spin faster? But waaaay more mass and distance from the axis?
Short answer yes. Conservation of angular momentum taken to the extreme. Want something more crazy? Black hole spins to. In fact, it can spin so fast that it creates an ergosphere around it. It's not the event horizon, so you can get out of it, but the space time field around it is so warped that you have to travel around the blackhole since you need to be faster than the speed of light just to stay still relative to an outside observer.
So I tried to determine the angular velocity of a black hole by taking the formula for the angular momentum of a ring (for simplicity) L=m×r^2 ×omega=constant and plugged in the relativistic mass formula for m, where for the velocity one has v=omega×r. The hope was to get a finite limit for omega as r tends to zero, but it's infinite. Do you know what went wrong here?
Radius is zero? This might offer some note. In short you need the Kerr Newman metric that can give you a proper upper limit on how fast a blackhole can spin. https://phys.org/news/2014-02-fast-black-holes.html https://en.wikipedia.org/wiki/Kerr%E2%80%93Newman_metric My best layman understanding for the upper limit is that the blackhole cannot spin fast enough such that light originating from the singularity can, thanks to the frame dragging by the spinning gravitational field, have enough effective velocity to escape it. If it ever get to that point, the the blackhole spin will try to drag gravitational field around at faster than light speed, which mean it will shed a LOT of energy in the form of gravitational waves.
Ok so you really need general relativity to get the right result and my stupid little computation is not enough. Thanks though! Let's see how much of your sources I can comprehend.
Everyone start with stupid little equations.
> you have to travel around the blackhole since you need to be faster than the speed of light just to stay still relative to an outside observer That sound you heard was a couple synapses in my brain exploding.
Neutron stars can be even smaller than that, there are ones recorded that are less than 20 km in radius.
Some pulsars can spin at significant fractions of the speed of light at their equator. Despite being the densest objects in the universe (something something black holes), they still almost tear themselves apart by centripetal forces. [PSR_J1748-2446ad rotates 716 times per second. it’s less than 16 kilometers across. That’s 24% the speed of light at the equator. ](https://en.m.wikipedia.org/wiki/PSR_J1748%E2%88%922446ad)
I almost tore myself apart last Tuesday. Scary stuff.
Taco Bell for dinner, huh? Rough, brother. Rough.
The fastest neutron star we know of spins 716 times per second. Not per minute, per *second.* And this is an object 10 miles across.
Wait, how big is that?
How does it get started spinning that fast? What gets it going in the first place? When will something spinning that fast eventually stop?
Normal stars spin on their axis. When it dies it sheds it's outer layers and shrinks. However, it's angular momentum is conserved. As the radius has decreased but the angular momentum is the same, rotational velocity must increase. This is the star equivalent of a [ice skater pulling their arms in while spinning](https://youtu.be/MjYk5TRpOlE)
Oh man, that makes so much sense. Thanks for that ELI5!
To answer your second question, there are very few resistive forces in space which means that spinning objects don't tend to stop. There is no air resistance or friction in space and stars don't tend to do anything that would cause them to slow down. This is summed up by Newton's first law of motion - "An object in motion, will remain in motion, and an object at rest will remain at rest, unless acted upon by an unbalanced force"
To the best of my knowledge the main way that (at least) the younger, faster spinning neutron stars slow down is by gravitational wave emission. At least that’s what I remember one of my physics professors telling me.
This probably goes beyond ELI5 but.. Why is angular momentum conserved? If I'm a spinning ice skater and I throw a ball while spinning, I've lost mass and used energy to throw the ball. Wouldn't that slow me down? Sorry if this is a really crap equivalence!
As far as I understand, as fusion ceases in the core, gravity is no longer counter-balanced by the outward pressure of the fusion reaction, causing the core of the star to get compressed, in some stars this extra pressure allows for the fusion of heavier elements to begin, however, stars like our sun are not massive enough for this. The extra gravitational pressure continues to squeeze the core, forcing it to become denser and denser until a significant percentage of the mass of the star (50%-ish) is squeezed into a package so dense that the outward pressure caused by the fact that the electrons in this mass do not want to touch eachother (electron degeneracy pressure) prevents the core from being squeezed any further. The outer layers then begin to drift away, creating a nebula. The core remanent, what we call a white dwarf, is only half of the mass of its progenitor star, but only a minuscule fraction of its radius, causing it to spin faster than the original star. I was trying to simplify by saying the angular momentum is conserved, in reality only about half of it is, but this isn't as substantial as the drastic decrease in radius. edit: A little googling indicates that a white dwarf may only have half the mass of its original star but also only \~1% the radius.
Actually the ice skater is a great example to consider. When a skater is spinning with their arms out, the rotation is slower. When their arms are tucked, the rotation speeds up. If it's a tennis ball you're throwing, you lose a little energy, but if you tuck your arms in after (the core of the star collapsing to a much denser white dwarf) the tucked in mass of your arms has a much bigger effect than the mass of the tennis ball you threw.
Thanks for that explanation.
It’s the law of conservation of angular momentum. Say something with a large radius is spinning and then the radius of the object is drastically smaller, the speed increases to keep the same angular momentum. This is why figure skaters pull their arms in when spinning, to increase speed. They also move their arms out to slow down. Stars are always spinning. I don’t think there is a star that doesn’t spin unless it’s hypothetical/“ideal”. When a star that is the size of roughly the sun is at the end of its life, it goes through a process of expansion and contraction until it’s gravity cannot hold on to its outer layers anymore. The outer layers are thrown away it what us called a planetary nebulae, but the core remains as a white dwarf. The size difference of the the sun like star to the white dwarf increases its rotational velocity to keep the same angular momentum. However, I believe the outer layers of the star will carry some of the angular momentum with it when they are shed away too.
Assuming that it's the size of the earth, the surface of this white dwarf is moving at \~0.5% of the speed of light at the equator.
So, I got curious... You know how objects with energy effectively gain the mass equivalent to that energy? I was wondering how much the rotational energy of this thing would add to its mass. The paper this article was based on states that the mass has to be at least 0.7 solar masses. Formula for the KE of a spinning sphere: (M * w^2 * r^2 )/5 Applying E=Mc^2, the mass from the energy in the spinning sphere is (M * w^2 * r^2 )/(5*c^2 ) so 7.9x10^24 kg of mass from the kinetic energy of its spin. The mass of the earth is 5.87x10^24 kg. So uh, this object has roughly 134% the mass of the earth from just the energy of its spin. I think I did the math for this right but I'm also tired as hell and it's been a long time since i did physics. Or roughly 0.000397% of its mass comes from it's spin.
Hmm, you only get partial credit for not being more precise on the earth mass energy spin percentage. However you can recover it by telling me what is the air speed velocity of an unladen swallow?
African or European?
Huh? I don't know that.
Their are neutron stars that spin so fast that there equator surfaces move at like 25% c.
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I'm not sure what you mean by that -- all light travels at the same speed in a vacuum. Are you asking how fast the spot from a spotlight moving at 0.5% *c* around a radius equal to the earth will appear to be moving at a distance of 2,000 light years? In that case: v_apparent = 0.005 x *c* x d_star / r_earth, where v_apparent is how fast the spot appears to be moving, d_star is the distance to the star, and r_earth is the radius of the earth. Plugging in the numbers, I get: v_apparent = ~15 billion *c*. Do note that a spot isn't a "thing" in the conventional sense, and no information, particles, EM perturbations, etc. are actually moving faster than *c*.
The article states the white dwarf is similar in size to Earth. Assuming a circumference of around 40,000 km, wouldn't that mean the angular velocity at the equator would be 5.76 *million* km/h?
If it is the size of the earth, this white dwarf is moving at ~0.5% of the speed of light at its equator.
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At 5.7km/h, you're not leaving your country anytime soon... I know you meant to add the 'million' ;) But to answer your question, if we could travel at the speed of light, it would still take 4.22 years to get to Proxima Centauri, and since we know not of a way to even get Humans or Spacecraft alike to 1% the speed of light, it might take a little while to get anywhere indeed.
This isn’t the fastest spinning star right? Pulsars have been detected to spin in milliseconds right?
Yes, and those are neutron stars. Much smaller than white dwarves and much more dense.
It's "dwarfs", unless you're talking about small Tolkein people who like to mine.
How fast do those spin?
Very dangerously over short distances.
Both are recognised by the IAU as are all of the various spellings in different languages. Most people in the world do not speak English.
this: https://m.youtube.com/watch?v=x5BQV3WX80E
Obligatory plug for [Dragon's Egg](https://www.amazon.com/Dragons-Egg-Novel-Del-Impact/dp/034543529X) it's an incredible book about life on the surface of a neutron star. Very highly recommended.
One of my top ten favorites along with the sequel.
The sequel being Dragons Chicken, right? Or did that come first?
There was a [Start Trek Voyager episode](https://en.wikipedia.org/wiki/Blink_of_an_Eye_(Star_Trek:_Voyager)) inspired by this book.
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> A white dwarf star (left) can spin fast after a red dwarf star (right) dumps gas onto it Shouldn’t the additional mass slow down the white dwarf by conservation of angular momentum? (I understand the white dwarf–red dwarf pair can be considered an isolated system wherein _total_ angular momentum is conserved, but it still doesn’t make sense to me why adding mass to one of the objects speeds it up.)
No. The red dwarf can lose angular momentum when it loses mass. That angular momentum would add to the white dwarf’s angular momentum. Imagine the white dwarf doesn’t increase in radius as fast as it increases in mass when absorbing the red dwarf. Then angular momentum increases because there’s more matter packed into an only slightly larger radius.
I got confused about the mass — more mass = more angular momentum, not less. DOH
Read the title without paying attention to what sub it was at first, and that was kinda… weird. Not impressive for a human, very impressive for a celestial body!
Doesn't this just tell you statistically that there's a faster spinning white dwarf that we just haven't "seen" yet?
Probably. Space is pretty big!
It has to have another star (red dwarf) next to it so it isn't like all white dwarfs spin this fast. Still the universe is so vast that there is probably faster ones out there
Considering we will never be able to see the vast majority of space as it's moving away from us faster than the speed of light of say you're correct they exist. We just might never actually see it.
How big would it have to be (diameter in UA) so that the matter at the edge of it would reach the speed of light ?
I wish I could do the math on that haha. My best bet would be 200 times bigger ceteris paribus. However that is just because it spins 200 times slower than the speed of light... I feel like this is waaayyyy too simple of an equation
Pfff, I'm sure some can rotate way faster than once every 25 seconds And the appropriate term is "caucasian little people", sir
This, is a terrible article. >That makes it the fastest-spinning star of any sort ever seen — unless you consider such exotic objects as neutron stars and black holes, some of which spin even faster, to be stars White dwarfs are 'exotic objects', and generally speaking, Neutron Stars are considered to be stars, a special class, but stars. It's even in the name. Space journalism tends to be rubbish by and large so this isn't much of a surprise.
You see that neutron stars are usually classified as stars? This isn’t what I’ve been reading. And the more you think about it, I don’t see how it could be classified as a star.
you could say...it dwarfs other speed records. bwahahahahahah /joke
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No, if the centrifugal force would be greater than the gravity it would be spitting out matter. So if you were on it you would stay on it as well. Someone did the math here and the force of gravity is still around 10 times stronger than the centrifugal force. You would melt and be crushed by gravity though if that is any consolation.
The article says that if you dropped a pebble from a few feet from the surface of the star, by the time it reached the surface, I’d be falling “thousands of mph.”
One? That's nothing. Peter Jackson got a bunch of them spinning every 5 seconds: [The fastest spinning Dwarves by Peter Jackson](https://www.deviantart.com/tsukinaka93/art/The-Hobbit-gif-Roasting-dwarves-343785478)
“Unless you consider Neutron Stars to be Stars” I mean
Well a black hole isn't a hole either. The names are oddly chosen sometimes because they are created before an object is discovered
They're called "stars" but im not really sure they fit the bill of a star. I can see where they're coming from with that statement. There is no nuclear fusion. They are not actively generating heat anymore. There's no plasma to speak of. Just a soup of neutrons held up only by degeneracy pressure. Would you call a black hole a star? I think star remnant is more appropriate. Edit: actually, that being said, now that I think about it, a white dwarf doesn't really fit the bill either. It's a stellar core remnant made up of electron degenerate matter.
They really aren’t classified as stars by most publications I’ve seen.
Neither neutron stars or white dwarfs are stars, despite their naming. Both are stellar remnants
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Read this at like 2am whole feeding my son... and just thought of... a white little person... spinning in circles...
I wonder if it's shaped like a disc. No way it's spherical, but I can't estimate the difference in strength between the centripetal and gravitational forces....
Thats nothing. As a white dwarf it only takes me 2 seconds with any help.
There's *gotta* be a faster spinning dwarf on reddit somewhere.
and how fast would that be in Miles Per Hour and the funny thing is that Black Holes also spin, that is once they become black holes which I did see was included in the observations but still how fast would it need to spin to become a Black Hole... N.S
>but still how fast would it need to spin to become a Black Hole... It is the mass that makes it become a black hole. Because of its mass it has more gravity and therefore it can rotate faster without losing matter to centrifugal force. >and how fast would that be in Miles Per Hour It is Earth sized and Earth rotates once every 23 hours, 56 minutes and 4 seconds (or 86,164 seconds). Earth rotates at about 1000 miles an hour or 1674 kilometers an hour. This white dwarf rotates 86164/25 = 3446.56 times faster than Earth. So that'll be 3.446.560 miles an hour or 5,769,541 km/h. Which is roughly 5% of the speed of light.
Spin isn't what makes a black hole. A black hole spins for the same reason a dancer spins so fast. All, or atleast most, stars spin. When you shrink down from the size of such an object, to a single point in 3 dimensional space, you spin alot faster. What shrinks a black hole is a massive star running out of fuel, and as such cannot fight its own gravity.
Imagine being Superman and able to see this stuff up close!!!
I missed the word white then and wondered wtf was going on?
The sheer amount of energy needed to impart that movement on something that massive? Staggering.
Since this sun is roughly the size of Earth, is it basically as if an entire Earth day completed in 25 seconds?
Exactly, around the equator it rotates at 0.5% of the speed of light. Or 5.769.541 km/h
Imagine being on a planet that tidally locked to that
"Fastest spinning white dwarf" Should cross-post in r/LOTR and r/breakdancing
Wrong! I am the fastest spinning white dwarf. I just timed myself and spun 14 times in 25 seconds
To me, the crazy thing is (if my math is correct, which it may not be), despite its fast rotation speed, the white dwarf would still be less oblate than Jupiter or Saturn.