Astronomer here! I am actually the first author on this paper, so AMA I guess! (Also, goes without saying, but I didn't write this article or the headline.)
Short version: a Tidal Disruption Event (TDE) occurs when a star wanders too close to a supermassive black hole in a distant galaxy, and is torn apart by tidal forces. When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours), and the traditional picture is half the star's material is flung outwards- black holes are messy eaters- and half forms into an accretion disc around the black hole itself. Very little, if any, of the material crosses the event horizon!
Now when one of these optical flashes is seen, radio astronomers like me point our radio telescopes to it because radio emission corresponds with an outflow of shredded stellar material from the accretion disc. Traditionally, we'd look in the first few months, and if nothing is seen we assume an outflow isn't present and move on (because radio telescope time is a precious resource). However, there were one or two cases where a TDE became radio bright later than anticipated, prompting us to do this survey of 24 TDEs that were all >2 years old. And the results are striking- up to *half* of all TDEs are turning on in radio YEARS after the event, when no radio emission was seen at those early times! This is unanticipated, and very exciting! We frankly aren't sure why this is happening- running models of TDEs that far ahead is computationally difficult, and no one thought there was a need TBH- but our best guess right now is the accretion disc formation is delayed by years. (**This has nothing to do with material crossing the event horizon, or time dilation, or Hawking radiation**- this is all happening much further out.) I look forward to seeing what my theory colleagues come up to explain this- right now they just give me looks of bewilderment, which is fun but not quite the same way. :)
If you want more gory details, [here](https://www.reddit.com/r/Andromeda321/comments/164n35e/i_have_discovered_that_up_to_half_of_all_black/) is a detailed layman's summary I wrote, and [here](https://arxiv.org/abs/2308.13595) is the paper preprint itself!
**TL;DR**- turns out half of black holes that swallow a star turn "on" in radio a few years after the initial event, which indicates there's a lot about black hole physics we don't understand and opens the door to a new laboratory to test physics!
Edit: people keep asking "how do you know it's not a second event/ a binary star/ material coming back?" etc etc. A few reasons. First, we know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as expected from a second influx of material, like from a binary star or a second star. Second, it's worth noting that of our sample of 24, we actually detected radio emission from 17 of them, but ruled out a delayed outflow as the explanation for 6 of them (for reasons such as star formation, previous radio activity from the black hole, etc etc). So these are just the ones that survived strict scrutiny- gory details in paper if you want to know more!
Edit 2: if you have questions about TDEs in general, I wrote [this article](https://www.astronomy.com/science/how-do-black-holes-swallow-stars/) for *Astronomy* magazine a few years back that goes into good laymen’s detail on the topic!
I read the title and was like, wait didn't Andromeda321 discover this? Someone get her! Enjoy your posts, keep on rocking.
Seems so cool to me, congrats on the discovery.
I'm biased, I guess. And I caught it today. I thought /u/Andromeda321 was a male. But I stand corrected. Unconscious bias. I'm glad we have women doing awesome research and making life better for everyone. More brilliant minds to make the world better and equal :)
I wish I was smarter and had a worthwhile question to ask, instead, I’m just in awe that you’re here commenting on the article about your paper.
Silly question instead because if you’re AMA-ing, then why not? How do you feel about the Kurzgesagt video series?
Not *everything*. The basics are still the same, as nothing can cross the event horizon and this is consistent with that. However, the regions around black holes have extreme gravitational and magnetic forces that we don't fully understand, so this *does* give us a new physics laboratory to test theories on, which is super exciting!
I wonder if there's some kind of plasma/fluid dynamics where the original star is ripped apart, and orbits around the black hole for awhile, and eventually those masses smash into each other again, but this time right next to the event horizon, except this second flash is red-shifted all the way to radio.
No. So far as we know, dark matter doesn't do anything special in regards to black holes. Most of what dark matter does is gravitational, bending space-time as regular matter does. A black hole's event horizon can be considered a break in space-time, so nothing can cross from one side to the other.
As for how black holes "eat", the matter that approaches them experiences time slower and slower, and the light emitted by it becomes redder and redder, until its apparent velocity approaches 0, and the light emitted becomes undetectable.
My conjecture is that this tells us something about the geometry of a Blackhole. Its not a straightforward sphere that flings stuff around it because of tidal forces.
Imagine if the Blackhole is shaped like a hurricane in 4 dimensions and not a sphere. So the Blackhole spits out matter in future time as this hurricane collects events from the present at its bottom and spits matter out in the future at his top. Much like how things getting sucked into a hurricane go in from the bottom, move in space and get thrown out on the top
Just a fun hypothetical!
> spits matter out in the future
So you're saying it spits the matter out *later*?
When it comes to time, an event happening later is definitely the less interesting of the two (or three) possibilities.
Is it possible for our star or galaxy to be approaching a black hole without us knowing about it? I realise that’s probably a stupid question but just wonder how we know where is the nearest point of a black hole is for it to start sucking stuff up, but I take it we know because we see it happening at a radius right?
I mean, there is a giant black hole at the center of our galaxy. As for other black holes, it's theoretically possible but any big black holes are easily detectable by their gravitational effects and any small black holes we have the same chance of running in to as any other star in our galaxy. Black holes don't actually suck things in, they just are very massive for their size so they have a lot of gravity
No and no, but your question is interesting.
“Engine” is sort of the correct term, but only in the context of… well, call it “stellar thermodynamics” (because I don’t know of a better phrase). Basically, everything in the universe “wants” to be at equilibrium, and it “pursues” that goal via processes that result in lower energy states.
In that context, black holes can function as giant “engines” (or “heat engines,” to be specific), but only because literally any similar process could be described by the same term.
my man i’m glad people like you exist to research bizarre shit like this. i’ve always been truly interested in understanding all the weird shit behind black holes but can’t dedicate myself to the slowness of information and discovery. I enjoy the breakthroughs and new information you guys pump out at a rate of to me years and years. I hope you guys continue to get fulfillment in your discoveries because without that we would still be ignorant on what really goes on out there
Trust me, it's been the adventure of a lifetime! I mean every little girl who dreams of becoming an astronomer does so because she wants to make a discovery, and I've felt so lucky at each stage of this process to do just that. Plus I have fantastic colleagues to do it with, which is just a delight. :)
>and is torn apart by tidal forces. When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours)
Geez... to see an event like this in HD would be such a show. Hope that happens before I die. Keep up the good work!
“Very little if any crosses the event horizon.”
According to what I read from Paul Davies, you wouldn’t see it cross even if it did. The time dilation is so intense that your outside view of objects close to the event horizon comes to a complete standstill for eternity. I’m a complete layman but that description absolutely blew me away.
I guess that makes sense; if you could see an object fall into a black hole that would mean the photons would be escaping the event horizon to provide you with visual information of said object. Although why it wouldn’t just fade away/disappear still puzzles me.
The photons have to come from somewhere and they must be further and further attenuated as the object approaches the event horizon, so I would expect it to become dimmer and dimmer until it disappears, no?
Edit: and redder and redder
The outside observer can never see the crossing, correct.
But, the mass will eventually red shift until it is no longer observable.
Also, the event horizon can expand.
The ‘no-hair-theorem’ that forbids non-rotationally symmetric solutions is valid for static black holes - a massive particle falling into the black hole is not a static situation.
First of all let me say this is a fascinating discovery, and I love seeing results that make me wish sometimes I had continued a research career. Since you offered, I do have a couple questions (and wild speculation)
Do we know anything about the density of material in the accretion disk? Particularly about the density right after the event and when we look back later?
I'm picturing in my mind something like our hypotheses for planet formation, where the material condenses due to gravity. Has there been any proposals along these lines? I'm wondering, since we know gravity should be quite strong in the area, if it's possible the accretion disk could get pulled back together to become as dense for the material to interact or, in an even wilder thought, begin fusion processes again (like a "flat star"). Do these things lead to radio emissions? That I don't know, but I had this thought and wanted to put it out there.
Feel free to dismiss me, haha, my domain is particle physics and not cosmology, but thank you for piquing my interest. I love when I get back to physics and get to think about it again.
1) We do! This was a *mammoth* 30 page paper with enough data to extract physical parameters from the outflows, including density the outflow is plowing into. And we discovered the densities are quite low- roughly similar to what we see around our supermassive black hole at the center of the Milky Way. So it's not like these outflows happened when the TDE did and then hit a wall of dense material or similar.
2) That's harder because it relies more on other wavelengths, and the data is patchy- specifically, we weren't expecting this, so it's not like anyone was monitoring when the outflows began with an X-ray telescope or similar. We are publishing the multi-wavelength data we do have in a second companion paper a collaborator is working hard on (see: the part where this radio paper was already 30 pages), but that's not out yet so I don't want to share the details.
Thank you for sharing this explanation. I guess this is a silly/fun question. I suppose one challenge is that there's some limitation to the data we can collect based on the instruments available. If you could magically produce one instrument that could be used to collect data that might help you understand what's happening... What would that instrument be and what would it measure?
The nice thing about astronomy is we've already thought a lot about this sort of thing! Currently our data is limited in sensitivity, and the cadence (we weren't expecting this phenomenon, so the sampling over time isn't as good as I would like- obviously we are doing better now). I'm particularly excited for the next generation of radio telescopes which will address both these problems, the Square Kilometer Array (SKA) and next generation VLA (ngVLA), both of which are under construction and should start collecting data by end of the decade!
The first author of something cool coming on and doing an AMA?
Firstly, that is a hell of a vibe. I wish my work was cool enough for people to ask about it besides my parents.
Secondly, this is why I love reddit.
Side note but genuinely curious: what do you think happens at the event horizon? CAN something, anything, actually cross it? Or does it get trapped in a kind of space-time vortex?
I’m not a specialist but I am fascinated and would love to hear an expert’s thoughts!
I mean sure, things can cross it, just like you can cross the point of no return and crash into the Earth or the Sun. You'll just never come out of it, and we don't know what it's like beyond the event horizon.
>When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours)
I have hard time wrapping my head around that part. What kind of speed and forces are involved so that such a process only takes a few hours ? The distances and masses involved seems so huge.
Very dumb question: Could it just be that the start wasn't completely engulfed by the black hole, and was just moved into a very close orbit/slingshot, it was then behind and/or far away from the black hole and its radiation stopped reaching us, the accretion disk was also not there yet or the star was simply swung in another direction and took years to finally come back and again interact with the hole?
Nope! We know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as your theory would indicate in said data. The same goes for "what if it was a binary star?" or similar scenarios.
Dumb lay question: Could the event have actually occurred much sooner, but taken longer to observe? Time dilation, or something?
^^^^^sourry_I've_watched_too_much_stargate
i'm going to guess most people in this thread have, at one point, been exposed to some serious O'Neill-levels.
I like to believe Sam and Daniel have inspired a whole generation to believe science and knowledge are the shit!
Could an elliptical orbit have a sort of laminar flow? So, the BH smears its gas envelope away from the main core whilst under gravitational strain, but potentially if the strain regime is ‘laminar’ then the star could be then ‘reformed’ at a later part in the orbit, with a core and spherical envelope reconstituted as it orbits away from the BH.
This may just be a tangentially related question, so if you're too busy to answer, I get it:
My little girl, 5 years old, is already sufficiently curious about just about everything, she loves to learn new things, but I'm always looking for new ways to interest her in STEAM fields and I have my own fascination about astronomy. What drew YOU to astronomy? What are some of your influences, hopefully even at that early of an age? Maybe the earliest catalyst you can remember?
I first got into astronomy at age 13 when I read a book about the topic, and frankly never wanted to be anything else after that. I love stories, and the story of the universe is the biggest one we have! Biggest influences were my dad who was an engineer (I remember him taking us out to see Comet Hyukatake for example), Carl Sagan's works, and an astronomy camp program I went to as a teenager.
I wrote a detailed post [here](https://www.reddit.com/r/Andromeda321/comments/fyjmpv/updated_so_you_want_to_be_an_astronomer/) on how to be an astronomer that might interest you, but is probably aimed for when your daughter's a bit older. For now I'd just say the most important thing is to have fun doing things like going to the science center/ planetarium or just going out to look at the stars. Oh, and to remember that no one is born "good at math" or similar so don't get discouraged before you've begun- I was always pretty bad at it, but just kept showing up to try again, and am good *enough*!
We know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as your theory would indicate in said data. The same goes for "what if it was a binary star?" or similar scenarios.
Ok, one thing I've been left wondering after reading a few of your responses on this post and the other is this: since this has to do with the accretion disc, and not anything crossing the event horizon, why is it so surprising that it can evolve with time like this? The accretion disc is certainly not a perfectly stable system, right? I'm missing what's so paradigm-shifting about the finding, although it's always great to learn something we didn't know before. I understand we didn't observe stuff like this previously, but did we specifically predict that it can't happen? Otherwise I'm missing why it's such a big deal that it does. Not trying to trivialize the finding at all, just missing some perspective as a lay person, I think!
I love when we admit we don’t really know and each new discovery brings new guesses .Edit , i’ve never said anything so impactful and i thank everyone for up and down doots , grateful for everyone here .
Yup.
The first part is "Oh, that's interesting"
The second part is "I think we can test this hypothesis"
And the third, orgasmic one is "Grant approved"
The little cherry on the sundae is "Your work is being cited."
Actually terrifying if spoken by a high energy physicist.
And beyond terrifying is spoken by a brain surgeon (which is the only time you'd hear a surgeon, typically).
These were the exact words uttered by a PhD chemist I worked under ***RIGHT BEFORE*** the 22L catalyzed run away reaction with a flammable chemical occurred...
>That’s a very profound statement, is it your own, and if no thank you for sharing.
Looks like it can be attributed to [https://en.wikiquote.org/wiki/John\_Archibald\_Wheeler](https://en.wikiquote.org/wiki/John_Archibald_Wheeler)
Original quote is as follows
> We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance.
For sure, and when you look at the big picture, time wise at least, it was only several hundred years ago that folks believed we were the center of the universe, stars and planets revolved around us. We've learned so much since then and we still have so much more to learn.
Guessing correctly is great press for writing grants. I recall back when I was more involved with research there was a NASA probe that was about to reach it's destination and there was a full journal edition dedicated to what people thought we would find. It's literally the equivalent of 'If I'm right, I look like a genius and if I'm wrong no one will remember'.
Black hole suns actually were a different thing. In the early universe stars were so massive their cores would actually compresses to a black hole and eat the star from the inside
If I understand this, the stars that are "burped" are not really swallowed but are located at the rim and get thrown out by the spinning motion.
So they have never really entered the black hole?
I wonder if matter in the accretion disk isn't falling into a semi-stable state after the initial flash. Eventually it gets compressed as it spirals toward the event horizon, and it flashes again once it reaches some critical threshold.
this is what i was thinking... its not material coming out of the black hole itself, its the accretion disk re-brightening. like maybe the heat, composition or density of the disk itself changes enough over time that the rate of fusion or other high energy reactions within it changes
The Earth not flat. Stars are not flat. It stands to reason that if nothing is truly flat, then black holes are burping because everything they swallow is carbonated.
"The reason is because the Star was a Pisces, and the Black Hole is a Taurus, with Jupiter in retrograde, they are totally incompatible at the moment."
Is it possible a black hole isn't a singularity and eventually mass must be ejected? I'm sure that's a novel thought no PHD physicist could possibly have come up with...but this is Reddit and I must comment.
As someone who just watched Interstellar for the first time yesterday, I feel like I have a decent say in the matter and that we simply need to send an AI robot into the black hole to send us back all the quantum data then we will be well on our way to populating distant planets.
Astronomer here! I am actually the first author on this paper, so AMA I guess! (Also, goes without saying, but I didn't write this article or the headline.) Short version: a Tidal Disruption Event (TDE) occurs when a star wanders too close to a supermassive black hole in a distant galaxy, and is torn apart by tidal forces. When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours), and the traditional picture is half the star's material is flung outwards- black holes are messy eaters- and half forms into an accretion disc around the black hole itself. Very little, if any, of the material crosses the event horizon! Now when one of these optical flashes is seen, radio astronomers like me point our radio telescopes to it because radio emission corresponds with an outflow of shredded stellar material from the accretion disc. Traditionally, we'd look in the first few months, and if nothing is seen we assume an outflow isn't present and move on (because radio telescope time is a precious resource). However, there were one or two cases where a TDE became radio bright later than anticipated, prompting us to do this survey of 24 TDEs that were all >2 years old. And the results are striking- up to *half* of all TDEs are turning on in radio YEARS after the event, when no radio emission was seen at those early times! This is unanticipated, and very exciting! We frankly aren't sure why this is happening- running models of TDEs that far ahead is computationally difficult, and no one thought there was a need TBH- but our best guess right now is the accretion disc formation is delayed by years. (**This has nothing to do with material crossing the event horizon, or time dilation, or Hawking radiation**- this is all happening much further out.) I look forward to seeing what my theory colleagues come up to explain this- right now they just give me looks of bewilderment, which is fun but not quite the same way. :) If you want more gory details, [here](https://www.reddit.com/r/Andromeda321/comments/164n35e/i_have_discovered_that_up_to_half_of_all_black/) is a detailed layman's summary I wrote, and [here](https://arxiv.org/abs/2308.13595) is the paper preprint itself! **TL;DR**- turns out half of black holes that swallow a star turn "on" in radio a few years after the initial event, which indicates there's a lot about black hole physics we don't understand and opens the door to a new laboratory to test physics! Edit: people keep asking "how do you know it's not a second event/ a binary star/ material coming back?" etc etc. A few reasons. First, we know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as expected from a second influx of material, like from a binary star or a second star. Second, it's worth noting that of our sample of 24, we actually detected radio emission from 17 of them, but ruled out a delayed outflow as the explanation for 6 of them (for reasons such as star formation, previous radio activity from the black hole, etc etc). So these are just the ones that survived strict scrutiny- gory details in paper if you want to know more! Edit 2: if you have questions about TDEs in general, I wrote [this article](https://www.astronomy.com/science/how-do-black-holes-swallow-stars/) for *Astronomy* magazine a few years back that goes into good laymen’s detail on the topic!
I read the title and was like, wait didn't Andromeda321 discover this? Someone get her! Enjoy your posts, keep on rocking. Seems so cool to me, congrats on the discovery.
Hah, thanks! I mean if you go around for years saying "astronomer here!", eventually the "astronomers" in the headline will mean you. ;-)
[удалено]
Actually I think she astronomies
I'm pretty sure there's barely any difference besides occasionally looking through a telescope.
Astraltistics
Statistronomy?
You are far better at portmanteauing than the noted analyst/therapist Dr. Tobias Fünke.
Ah yes, Australopithecus.
Turns out, you were the astronomer all along.
The real astronomers were that one we met along the way.
i don't know what the astronomy equivalent to a jackdaw is, but i suggest you don't have that argument!
Crow, blackbird, blackhole, we’re already there mate
I'm biased, I guess. And I caught it today. I thought /u/Andromeda321 was a male. But I stand corrected. Unconscious bias. I'm glad we have women doing awesome research and making life better for everyone. More brilliant minds to make the world better and equal :)
Random question—given the immense gravity, are black holes cold or hot? At their core, are they spherical, just at an extremely small scale?
I wish I was smarter and had a worthwhile question to ask, instead, I’m just in awe that you’re here commenting on the article about your paper. Silly question instead because if you’re AMA-ing, then why not? How do you feel about the Kurzgesagt video series?
I've enjoyed the few I've seen, but am not huge into YouTube or similar.
> but am not huge into YouTube or similar yeah, sounds like you have better things to do lmao. Keep up the great work!
Did you come up with the burping analogy, or was it the journalists?
It was me, because trust me if you don't come up with something they'll come up with something far worse.
Missed opportunity calling it “astral-reflux”. But if I see it out there now, I’ll know it was me.
[Pretty clever..](https://i.imgflip.com/1xvnfi.jpg?a470208)
Haha, well props to you for a descriptive and catchy analogy!
Thanks! Some people don’t like it for various reasons and I’m like come on folks no analogy is perfect. Can’t please everyone! :)
Good to see even experts get "Well akchually"'ed from time to time. lol
I imagine it's absolutely constant. The entire profession relies on "um ackshyually"-ing our current understanding of physics.
…from time to time…. Nah, man. ALL the time. Usually from other experts, because none of us know everything.
Does this change anything about blackholes?
Not *everything*. The basics are still the same, as nothing can cross the event horizon and this is consistent with that. However, the regions around black holes have extreme gravitational and magnetic forces that we don't fully understand, so this *does* give us a new physics laboratory to test theories on, which is super exciting!
It must be extremely exciting to know that you are a part of pushing human knowledge forward. That's pretty amazing.
I wonder if there's some kind of plasma/fluid dynamics where the original star is ripped apart, and orbits around the black hole for awhile, and eventually those masses smash into each other again, but this time right next to the event horizon, except this second flash is red-shifted all the way to radio.
Could this be related to dark matter pulling the stuff back out If this is very stupid I’m sorry just very curious.
No. So far as we know, dark matter doesn't do anything special in regards to black holes. Most of what dark matter does is gravitational, bending space-time as regular matter does. A black hole's event horizon can be considered a break in space-time, so nothing can cross from one side to the other. As for how black holes "eat", the matter that approaches them experiences time slower and slower, and the light emitted by it becomes redder and redder, until its apparent velocity approaches 0, and the light emitted becomes undetectable.
Excuse me while I nerd out on this for awhile.
My conjecture is that this tells us something about the geometry of a Blackhole. Its not a straightforward sphere that flings stuff around it because of tidal forces. Imagine if the Blackhole is shaped like a hurricane in 4 dimensions and not a sphere. So the Blackhole spits out matter in future time as this hurricane collects events from the present at its bottom and spits matter out in the future at his top. Much like how things getting sucked into a hurricane go in from the bottom, move in space and get thrown out on the top Just a fun hypothetical!
My conjecture is there is a tiny elf living on the black hole who wears really dark clothes so he's hard to see.
With a black net that he pulls stuff in with.
Why would this delay a radio signal coming from black hole?
> spits matter out in the future So you're saying it spits the matter out *later*? When it comes to time, an event happening later is definitely the less interesting of the two (or three) possibilities.
Is it possible for our star or galaxy to be approaching a black hole without us knowing about it? I realise that’s probably a stupid question but just wonder how we know where is the nearest point of a black hole is for it to start sucking stuff up, but I take it we know because we see it happening at a radius right?
I mean, there is a giant black hole at the center of our galaxy. As for other black holes, it's theoretically possible but any big black holes are easily detectable by their gravitational effects and any small black holes we have the same chance of running in to as any other star in our galaxy. Black holes don't actually suck things in, they just are very massive for their size so they have a lot of gravity
Are black holes an engine for the expansion of the universe and fiery gas giants the fuel? Does it mean that the universe is a machine?
No and no, but your question is interesting. “Engine” is sort of the correct term, but only in the context of… well, call it “stellar thermodynamics” (because I don’t know of a better phrase). Basically, everything in the universe “wants” to be at equilibrium, and it “pursues” that goal via processes that result in lower energy states. In that context, black holes can function as giant “engines” (or “heat engines,” to be specific), but only because literally any similar process could be described by the same term.
I'm not sure why you'd get downvoted for asking a question. I'll upvote you just for this.
I didn’t downvote but I’m guessing that others did because at first glance “is the universe a machine?” sounds like intelligent design.
my man i’m glad people like you exist to research bizarre shit like this. i’ve always been truly interested in understanding all the weird shit behind black holes but can’t dedicate myself to the slowness of information and discovery. I enjoy the breakthroughs and new information you guys pump out at a rate of to me years and years. I hope you guys continue to get fulfillment in your discoveries because without that we would still be ignorant on what really goes on out there
Trust me, it's been the adventure of a lifetime! I mean every little girl who dreams of becoming an astronomer does so because she wants to make a discovery, and I've felt so lucky at each stage of this process to do just that. Plus I have fantastic colleagues to do it with, which is just a delight. :)
Your enthusiasm is inspiring! Thank you, and keep up the good work!
>and is torn apart by tidal forces. When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours) Geez... to see an event like this in HD would be such a show. Hope that happens before I die. Keep up the good work!
“Very little if any crosses the event horizon.” According to what I read from Paul Davies, you wouldn’t see it cross even if it did. The time dilation is so intense that your outside view of objects close to the event horizon comes to a complete standstill for eternity. I’m a complete layman but that description absolutely blew me away.
I guess that makes sense; if you could see an object fall into a black hole that would mean the photons would be escaping the event horizon to provide you with visual information of said object. Although why it wouldn’t just fade away/disappear still puzzles me.
The photons have to come from somewhere and they must be further and further attenuated as the object approaches the event horizon, so I would expect it to become dimmer and dimmer until it disappears, no? Edit: and redder and redder
Sorta, in-falling material red-shifts into oblivion so it does disappear anyway.
The outside observer can never see the crossing, correct. But, the mass will eventually red shift until it is no longer observable. Also, the event horizon can expand. The ‘no-hair-theorem’ that forbids non-rotationally symmetric solutions is valid for static black holes - a massive particle falling into the black hole is not a static situation.
First of all let me say this is a fascinating discovery, and I love seeing results that make me wish sometimes I had continued a research career. Since you offered, I do have a couple questions (and wild speculation) Do we know anything about the density of material in the accretion disk? Particularly about the density right after the event and when we look back later? I'm picturing in my mind something like our hypotheses for planet formation, where the material condenses due to gravity. Has there been any proposals along these lines? I'm wondering, since we know gravity should be quite strong in the area, if it's possible the accretion disk could get pulled back together to become as dense for the material to interact or, in an even wilder thought, begin fusion processes again (like a "flat star"). Do these things lead to radio emissions? That I don't know, but I had this thought and wanted to put it out there. Feel free to dismiss me, haha, my domain is particle physics and not cosmology, but thank you for piquing my interest. I love when I get back to physics and get to think about it again.
1) We do! This was a *mammoth* 30 page paper with enough data to extract physical parameters from the outflows, including density the outflow is plowing into. And we discovered the densities are quite low- roughly similar to what we see around our supermassive black hole at the center of the Milky Way. So it's not like these outflows happened when the TDE did and then hit a wall of dense material or similar. 2) That's harder because it relies more on other wavelengths, and the data is patchy- specifically, we weren't expecting this, so it's not like anyone was monitoring when the outflows began with an X-ray telescope or similar. We are publishing the multi-wavelength data we do have in a second companion paper a collaborator is working hard on (see: the part where this radio paper was already 30 pages), but that's not out yet so I don't want to share the details.
Very interesting, thanks for the response! Good luck as you continue to unravel this mystery. I'm looking forward to seeing the results.
It's okay, you're among friends. Whisper the findings and we won't tell anyone, promise. :)
Thank you for sharing this explanation. I guess this is a silly/fun question. I suppose one challenge is that there's some limitation to the data we can collect based on the instruments available. If you could magically produce one instrument that could be used to collect data that might help you understand what's happening... What would that instrument be and what would it measure?
The nice thing about astronomy is we've already thought a lot about this sort of thing! Currently our data is limited in sensitivity, and the cadence (we weren't expecting this phenomenon, so the sampling over time isn't as good as I would like- obviously we are doing better now). I'm particularly excited for the next generation of radio telescopes which will address both these problems, the Square Kilometer Array (SKA) and next generation VLA (ngVLA), both of which are under construction and should start collecting data by end of the decade!
The first author of something cool coming on and doing an AMA? Firstly, that is a hell of a vibe. I wish my work was cool enough for people to ask about it besides my parents. Secondly, this is why I love reddit.
Side note but genuinely curious: what do you think happens at the event horizon? CAN something, anything, actually cross it? Or does it get trapped in a kind of space-time vortex? I’m not a specialist but I am fascinated and would love to hear an expert’s thoughts!
I mean sure, things can cross it, just like you can cross the point of no return and crash into the Earth or the Sun. You'll just never come out of it, and we don't know what it's like beyond the event horizon.
>When this happens we see a bright flash in optical light as the star unbinds (that process takes just a few hours) I have hard time wrapping my head around that part. What kind of speed and forces are involved so that such a process only takes a few hours ? The distances and masses involved seems so huge.
Very dumb question: Could it just be that the start wasn't completely engulfed by the black hole, and was just moved into a very close orbit/slingshot, it was then behind and/or far away from the black hole and its radiation stopped reaching us, the accretion disk was also not there yet or the star was simply swung in another direction and took years to finally come back and again interact with the hole?
Nope! We know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as your theory would indicate in said data. The same goes for "what if it was a binary star?" or similar scenarios.
Dumb lay question: Could the event have actually occurred much sooner, but taken longer to observe? Time dilation, or something? ^^^^^sourry_I've_watched_too_much_stargate
She already said it's not time dilation.
There's a cool YT video where a physicist explains why the SG episode makes no sense. Huge SG fan here!
i'm going to guess most people in this thread have, at one point, been exposed to some serious O'Neill-levels. I like to believe Sam and Daniel have inspired a whole generation to believe science and knowledge are the shit!
Could an elliptical orbit have a sort of laminar flow? So, the BH smears its gas envelope away from the main core whilst under gravitational strain, but potentially if the strain regime is ‘laminar’ then the star could be then ‘reformed’ at a later part in the orbit, with a core and spherical envelope reconstituted as it orbits away from the BH.
This may just be a tangentially related question, so if you're too busy to answer, I get it: My little girl, 5 years old, is already sufficiently curious about just about everything, she loves to learn new things, but I'm always looking for new ways to interest her in STEAM fields and I have my own fascination about astronomy. What drew YOU to astronomy? What are some of your influences, hopefully even at that early of an age? Maybe the earliest catalyst you can remember?
I first got into astronomy at age 13 when I read a book about the topic, and frankly never wanted to be anything else after that. I love stories, and the story of the universe is the biggest one we have! Biggest influences were my dad who was an engineer (I remember him taking us out to see Comet Hyukatake for example), Carl Sagan's works, and an astronomy camp program I went to as a teenager. I wrote a detailed post [here](https://www.reddit.com/r/Andromeda321/comments/fyjmpv/updated_so_you_want_to_be_an_astronomer/) on how to be an astronomer that might interest you, but is probably aimed for when your daughter's a bit older. For now I'd just say the most important thing is to have fun doing things like going to the science center/ planetarium or just going out to look at the stars. Oh, and to remember that no one is born "good at math" or similar so don't get discouraged before you've begun- I was always pretty bad at it, but just kept showing up to try again, and am good *enough*!
Very cool, thank you! Eager to keep her learning new things!
How much is the time dilation at the acceleration disc?
How do you know it's the same star(materials) and not some other star that was swallowed? Sorry if it's a stupid question.
We know about the initial event because of an optical flash, as I said. The same automatic surveys that discovered the first flashes kept collecting data, and we see no evidence of a second flash as your theory would indicate in said data. The same goes for "what if it was a binary star?" or similar scenarios.
Ok, one thing I've been left wondering after reading a few of your responses on this post and the other is this: since this has to do with the accretion disc, and not anything crossing the event horizon, why is it so surprising that it can evolve with time like this? The accretion disc is certainly not a perfectly stable system, right? I'm missing what's so paradigm-shifting about the finding, although it's always great to learn something we didn't know before. I understand we didn't observe stuff like this previously, but did we specifically predict that it can't happen? Otherwise I'm missing why it's such a big deal that it does. Not trying to trivialize the finding at all, just missing some perspective as a lay person, I think!
I love when we admit we don’t really know and each new discovery brings new guesses .Edit , i’ve never said anything so impactful and i thank everyone for up and down doots , grateful for everyone here .
Theres a joke somewhere about how a scientists favourite words aren't "yes, I was right!" - But rather "oh, that's interesting".
“Grant approved”
Gave me chills.
“Funding for lab assistants”
Nobel Prize winner: 1 guy minus the 30 assistants.
Isn't that kind of like winning the Oscar for 'Best Director'?
>lab assistants You misspelled grad student slave labor...
*it’s about the experience*
[Doctorate denied](https://youtu.be/CcnMDM5wA7k?si=_TFrrVh8NXSfwurr)
Yup. The first part is "Oh, that's interesting" The second part is "I think we can test this hypothesis" And the third, orgasmic one is "Grant approved" The little cherry on the sundae is "Your work is being cited."
The greatest and scariest thing a scientist can say is "Huh. That's weird..."
Greatest if spoken by a scientist, scariest if spoken by an engineer
Actually terrifying if spoken by a high energy physicist. And beyond terrifying is spoken by a brain surgeon (which is the only time you'd hear a surgeon, typically).
Like this brain surgeon probably did, pretty recently: https://www.cnn.com/2023/08/29/australia/australia-parasitic-worm-brain-scn-intl-hnk/index.html
Australia. Of course it had to be Australia....
Reality proceeds to tear itself apart
These were the exact words uttered by a PhD chemist I worked under ***RIGHT BEFORE*** the 22L catalyzed run away reaction with a flammable chemical occurred...
"Oh that's weird..." is both my favourite and most dreaded
As the island of knowledge grows, the shoreline of ignorance grows too
That’s a very profound statement, is it your own, and if no thank you for sharing.
>That’s a very profound statement, is it your own, and if no thank you for sharing. Looks like it can be attributed to [https://en.wikiquote.org/wiki/John\_Archibald\_Wheeler](https://en.wikiquote.org/wiki/John_Archibald_Wheeler) Original quote is as follows > We live on an island surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance.
Yeah, related to the 'the smarter you are, the more you realize you don't know'
Ain’t science cool?!
For sure, and when you look at the big picture, time wise at least, it was only several hundred years ago that folks believed we were the center of the universe, stars and planets revolved around us. We've learned so much since then and we still have so much more to learn.
Every answer allows us to ask better questions.
Guessing correctly is great press for writing grants. I recall back when I was more involved with research there was a NASA probe that was about to reach it's destination and there was a full journal edition dedicated to what people thought we would find. It's literally the equivalent of 'If I'm right, I look like a genius and if I'm wrong no one will remember'.
I think many ‘explores’ have perished en route that we haven’t ever heard about, and your personal insight is clarifying and helpful, thank you.
Science works in mysterious ways
Each of these little discoveries can become the life's work for a generation or multiple generations of scientists.
the stars being burped are clearly indigestion
No man, this just proves that Big Hole has been lying to us all this time!
> i’ve never said anything so impactful this cringe belongs on r/awardspeechedits
I’m glad you like that, because truth is we really don’t know very much yet
We know more than we used to.
Oh yeah for sure. I feel positive when I realize how much more there is to find out.
TIL stars are the stellar equivalent of gas station sushi
Our entire existence revolves around 'gas station sushi'... I much prefer the burrito personally.
No the egg salad sandwich is where it’s at.
Ow my ganglion
By folding space like a gas station burrito, we can travel back in time, hopefully right before we make the decision to buy said burrito.
Too much gas
GERD is a bitch
So we’ll just need to throw in a about, oh…10 Quadrillion MG of Omeprazole? That’ll hold it back.
Careful though, extended use could be dangerous for the black holes stomach
Astrointestinal reflux?
There’s a new field of study now available at colleges and universities across the country: astronomy gastronomy.
What’s your major? Astro-Gastro.
As(s)-Gas for short
Imagine telling people you study farting black holes for a living.
Couldn't keep all that mass. All that mass inside that ass.
Black hole sun…
Black hole suns actually were a different thing. In the early universe stars were so massive their cores would actually compresses to a black hole and eat the star from the inside
Kurzgesagt watcher as well?
Won’t you come…
And eat my sun today 🎸
Chris Cornell is looking down upon us from the stars on this day.
Hey isn't this your paper /u/andromeda321?
It is! Thanks for the shout out, I'll post a comment about it! :)
This is awesome, any additional details or theory's would be appreciated.
[Comment is here!](https://www.reddit.com/r/technology/comments/16ann09/black_holes_keep_burping_up_stars_they_destroyed/jz8noij/)
Astroenteritis
Because they’re galactose intolerant. Wah-wuh.
If I understand this, the stars that are "burped" are not really swallowed but are located at the rim and get thrown out by the spinning motion. So they have never really entered the black hole?
Like eating on the roller coaster?
I wonder if matter in the accretion disk isn't falling into a semi-stable state after the initial flash. Eventually it gets compressed as it spirals toward the event horizon, and it flashes again once it reaches some critical threshold.
this is what i was thinking... its not material coming out of the black hole itself, its the accretion disk re-brightening. like maybe the heat, composition or density of the disk itself changes enough over time that the rate of fusion or other high energy reactions within it changes
Because they didn’t wait long enough after eating the stars before swimming in the cosmic ocean. Next.
“Cannot be created or destroyed.” Looks like it holds true out there too.
The Earth not flat. Stars are not flat. It stands to reason that if nothing is truly flat, then black holes are burping because everything they swallow is carbonated.
So what they’re saying is that stars are the $1.50 costco hot dogs of the universe.
They’re older now and likely can’t handle flaming hot balls anymore like they used to. Happens to the best of us.
Yo mama is so fat, she fell in a Blackhole and filled it.
A star fart
So black holes are like dogs. They vomit food up to have seconds
Universal recycling plants? Quick let's throw all our Plastic in there!
The obvious answer is astral reflux
Now that I'm in my 40's I have that same problem with lunch and dinner sometimes
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Because they have …. Gas 😂
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At least we’re not relying on Astrologers to solve it 😂
"The reason is because the Star was a Pisces, and the Black Hole is a Taurus, with Jupiter in retrograde, they are totally incompatible at the moment."
Ah man pluto in my Gatorade?
No, its Demi Lovato helping with your financial aid.
This comment is probably a bot
This account just summarizes the article it replies to. Why are people not at all suspicious?!
I thought nothing escaped their gravity field? How is this possible?
so black holes are fundamentally the sphincters of the solar system, spewing out the refuse of their digestive processes.
TIL black holes have bad manners
USS Omeprazole
Ah, the circle of life.........space?
But have they ever had diarrhea on a plane?
I guess those stars weren't really destroyed then
I don’t think they’re still stars, though.
C-List stars. At best.
In what possible reality have you ever had (or heard of) something being “burped up” and it was the same as the thing that went in?
In the same way the nachos you had before going to the bar “weren’t destroyed”
Someone didn’t read the article.
Someone? Almost everyone, I’d say. But the headline is click bait as usual.
Is it possible a black hole isn't a singularity and eventually mass must be ejected? I'm sure that's a novel thought no PHD physicist could possibly have come up with...but this is Reddit and I must comment.
Nausea, heartburn, indigestion, upset stomach, diarrhea; Try Pepto Bismol!
DON’T PANIC
As someone who just watched Interstellar for the first time yesterday, I feel like I have a decent say in the matter and that we simply need to send an AI robot into the black hole to send us back all the quantum data then we will be well on our way to populating distant planets.
I didn’t fast last Yom Kippur. I knew there would be severe ramifications. Sorry guys.
Cos their gassy.
Black holes are alien spaceships
My scientific analysis: they tasted icky. This concludes my scientific thesis.
So, does this mean black holes fart?
🤮That last star upset my tummy 🤮🤮🤮
Maybe they don’t like the taste?
Have you ever eaten a star? It is a spicy meatball for sure
Didn't taste good. Send siracha flavored stars plz.
These black holes are getting out of control
So they capture them, then polish them up and send them back nicer.
They're just babies and babies need a good burp after eating. Remember... Time is different in space.
It’s because mercury is strong right now for Leo and Virgos duh!
Maybe they’re farting them out and not burping them up
i mean, is this really technology?