Bright flash is a black hole jet pointing at Earth, astronomers say | Hacker News Reader

Bright flash is a black hole jet pointing at Earth, astronomers say

phys.org

236 pointswglb174 comments

Typically Active Galactic Nuclei (AGN) with the jets pointed directly at Earth are referred to as Blazars. (https://farm9.staticflickr.com/8300/7754600044_e7635a1c8f.jp...)

But this event seems to be something a little different. Its a lot closer to us than a lot of blazars typically are, and the emission seems to infer a different source than is typically seens for blazars.

Quite an interesting paper, will be cool to see how this might change our understanding of AGN and accretion of matter onto such objects.

>referred to as Blazars

For me, legitimately one of the best names for anything ever. First time I heard the word it gave me goosebumps lol.

I'm partial to Thagomizer.

https://en.wikipedia.org/wiki/Thagomizer

> The term thagomizer was coined by Gary Larson in jest. In a 1982 The Far Side comic, a group of cavemen are taught by a caveman lecturer that the spikes on a stegosaur's tail were named "after the late Thag Simmons".

My 5 year old surprised me when she pointed to the spikes on a dinosaur tail and said ‘that’s the thagomizer’. I knew about the cartoon and that it’d been adopted as the official term, but somehow wasn’t expecting it to be taught in primary schools as standard dino anatomy.

thagomizer is a lot more fun to say than something technical like "distal tail bone spikes" or something similar.

Distal Coccygeal Osteophytes

I love that band.

I met their lead singer, Spike.

The name comes from BL Lacertae (the prototypical object) and Quasar (A kind of Active Galactic Nucleus, that name is for quasi stellar, which it really isn't...)

How about blazer? Any reaction to that?

So you could say they're... Star Blazars?

"We’re off to outer space... We’re leaving mother Earth... To save, the human race! Our Star Blazers!"

(OK, so the spelling is off. But since I'm going to be humming this the rest of the day, might as well see if there's some 80s kids out there that will join in with me.)

> seems to infer

You mean "seems to imply".

> Its a lot closer to us than a lot of blazars typically are

And the article says:

> The source is also the farthest TDE ever detected, at some 8.5 billion lights years away—more than halfway across the universe.

So this is the farthest TDE, but most Blazars are even further away than "halfway across the universe"?

88% of the volume of the universe is more than halfway across the universe. Assuming a spherical universe with us at the center.

Observable Universe.

There's likely considerably more unobservable Universe.

Blazars are some of the brightest objects in the sky, and some of the furthest from us (think the furthest object I studied was at a redshift of 6 or so). They can also be difficult to pinpoint in terms of distance due to their flat spectra.

https://en.wikipedia.org/wiki/Old-fashioned_(short_story)

An Asimov story about stranded astro-miners who throw rocks into a black hole to generate x-rays with the hopes that they will be spotted by observers back on Earth. The throws are timed to spell out S-O-S.

Sorry for a stupid question but I’ve seen it repeated on the internet many times that we can never observe anything actually falling into a black hole because it takes forever to actually fall in due to time lengthening the closer it gets. Is that true? It has never made sense to me, since we see effects of black holes all the time.

Once a black hole -- a collapsar -- forms, and you want to toss something into it, it is best to imagine two timelines.

From the point of view of the object being hurled into the black hole, things proceed more or less normally: you accelerate as you fall, but light behind you becomes curiously more blue and brighter. You eventually reach the event horizon, which ought to be called EH-sub-0, because it is only the first event horizon. It might be helpful to think of a black hole's interior as infinitely layered event horizons, event horizons "all the way down." You'd note a restriction of movement -- "up" (away from the black hole) is no longer a possibility; every direction is some variation of down, perhaps down and to the left, down and east, whatever, but always down. Eventually tidal forces take over depending on the size of the thing -- you might notice them before or after the outmost event horizon, and "spaghettification" occurs even as you are pummeled with X-rays and gamma radiation from behind (millennia of impacting photons blueshifted and jammed into a smaller timeline).

From the outside, however, your astronaut or thrown Cylume lightstick becomes more and more red, and dim, slowly approaching that event horizon but you'll never see it get there as it now emits infrared and not much of that. You switch on your FLIR and you can see it, for a while, but it grows dimmer and eventually disappears off of that. Eventually it emits very weak radio waves, and you lose track of the thing, but even if you spent a million years building longer and longer antennae, you'd never see it hit.

The effects you see of a black hole are 1) gravitational lensing (photons bending in their trajectory around the exterior of a black hole, just above the outermost event horizon), 2) the formation of an accretion disc (as matter swirls into it, growing hot from friction and compression), 3) absolute blackness if you managed to get a "transit" of something particularly large across a light path, 4) other knock-on gravitational effects, like disturbed orbits.

> You'd note a restriction of movement -- "up" (away from the black hole) is no longer a possibility; every direction is some variation of down, perhaps down and to the left, down and east, whatever, but always down.

You'd notice if you were doing calculations as you fell. Locally, nothing particularly special happens at the event horizon, as far as I understand; just, past that point, all future directions lead to the centre of the black hole. (Plenty of past directions still point outwards, so you wouldn't even see anything particularly special unless you were paying close attention to, say, the apparent shape of the black hole.)

This is a little confusing to me.

Could the gravity not be the parabolic reflector? The actual black hole itself is creating the "dent" in spacetime and the gravitational lensing is "pushing" the forces in a parabolic manner. Since that gravitational lensing keeps things focused for a very huge distance, it could keep the beam collimated, no?

Sorry, I love this topic, but I don't know much about physics. This might be a really dumb question.

Parabolas have a nicely defined axis. Non-rotating, uncharged black holes are spherically symmetrical, so no parabola.

The lensing happens in all directions.

I understand now, thank you for explaining

What happens to the matter at the edge of the event horizon when the event horizon grows?

And wouldn’t the density of in-falling matter quickly exceed what is physically possible?

1) From the outside, you wouldn't see anything, because that matter is already emitting maybe one enormous radio wave-sized photon per year. But from the view of someone falling in, you might get an imperceptible jump like you had gotten slightly closer. Remember, if you dropped something Earth-massed into a black hole (say on the other side), the black hole wouldn't grow even a full centimeter in radius. This would be very difficult to notice in practice. "Kind of a "stutter" as you approach, maybe.

2) No. What's physically possible is the ridiculousness of a neutron star's core. If you surrounded an event horizon with something of that density with the snap of your fingers (say one hemisphere), well, just as suddenly you would have a local amount of mass that would be quite formidable and the event horizon would seamlessly expand in that direction. You wouldn't see it, just watch your half-neutron-star shell wink out as you have "too great" a concentration of mass in a particular volume. See #1.

> Is that true?

Probably. We don't know for sure because quantum effects might change things, and we don't yet have a theory of quantum gravity. The event horizon of a black hole is pretty much the one place in the universe where the effects of quantum gravity are most likely to manifest themselves, so one should hedge one's bets when making predictions in their vicinity.

> It has never made sense to me, since we see effects of black holes all the time.

Falling into a black hole is different from falling into a regular gravitational field. All kinds of weird shit happens before you reach the event horizon. Among other things, tidal forces rip you apart, heat you up, and turn you into a plasma. That plasma emits radiation, and that is what you see (because all that happens outside the event horizon).

It all depends on the size of the black hole. HUGE black holes have weak tidal forces.

True, but the hole under discussion here is not one of those. (And it's important to note that big holes have weak tidal forces at the event horizon. They still probably have pretty significant tides close to the singularity, but God only knows what actually goes on in there).

> but the hole under discussion here is not one of those.

That’s not correct: It’s a supermassive black hole at the center of a galaxy; the tidal forces will be weak at the event horizon.

Yeah, I know that's what the news reports say, but I'm pretty sure they got it wrong. A galactic hole doesn't emit radiation (except perhaps Hawking radiation) because its tidal forces are too weak.

Isn't charge a conserved quantity? Tidal forces may be the least of your problems. The mass of millions of disrupted stars rotating at near the speed of light on powerful charged magnetic fields around the event horizon are apt to be a much bigger problem.

You'll never directly see them fall in, but you will see them "disappear" pretty quickly as the light is redshifted past the point of visibility, etc.

The more sensitive whatever tool you are using to detect the photons is, the longer you can watch, and something that approaches infinite sensitivity would be able to see you for a time period that also approaches infinity, but outside of the realm of the theoretical, anything falling in to the black hole will wink out of existence in a fairly large hurry once it reaches the event horizon.

But things like accretion disks and these relativistic jets are happening outside of the event horizon, so they're not subject to these same concerns to begin with. For example, the accretion disk of Sagittarius A*, the supermassive black hole at the center of our galaxy, has an accretion disk that is roughly 1/100th of a light year, or about 25 times the size of our solar system. The event horizon, however, is only about 16 million miles - or a roughly 1/6th the distance between the sun and the earth. (These numbers are based on our current best estimates - and those estimates have changed frequently over the past 20 years as we get better data, but the general scale should be quite accurate)

AFAIK you never see it falling in as it just slows and turns into more red, but slowly.

The effects aren't limited to just falling in. Once you pass the event horizon it's game over, but remarkably little matter from, say a star falling in, will actually reach the event horizon. For one example, a lot of particles get swept up in the magnetic maelstrom surrounding spinning black holes and are shot away from the poles at near the speed of light. That's what we're seeing here.

https://math.ucr.edu/home/baez/physics/Relativity/BlackHoles...

> So if you, watching from a safe distance, attempt to witness my fall into the hole, you'll see me fall more and more slowly as the light delay increases. You'll never see me actually get to the event horizon. My watch, to you, will tick more and more slowly, but will never reach the time that I see as I fall into the black hole. Notice that this is really an optical effect caused by the paths of the light rays.

> This is also true for the dying star itself. If you attempt to witness the black hole's formation, you'll see the star collapse more and more slowly, never precisely reaching the Schwarzschild radius.

I don't understand everything but it seems that the falling guy tends towards the event horizon, getting slower and slower relative to the observer, and never reaching it from the observer's point of view?

Edit: this applies when observing something falling into the black hole. It doesn't apply to faraway objects that deviate because of the black hole's gravity well, so we can observe most of a black hole's effects.

Yes they say this but how do we see the jet in the original linked article haha?

The types of highly visible bright lights coming from black holes are not actually coming from inside the black hole. The gravitational potential of the well is so incredibly high that objects falling through it gain immense amounts of energy, thus giving of very high energy radiation, i.e. x-rays.

No source now, but I think I've read that the jet is matter that's far enough from the black hole to escape it, accelerated during its rotation.

The wiki page isn't very clear about how the jet is created: https://en.wikipedia.org/wiki/Tidal_disruption_event

As I understand it (based entirely on pop sci books and articles) they're purely from the accretion disk i.e. nothing inside the event horizon. I don't think the exact mechanism is agreed upon beyond that.

Think about the tidal forces that a piece of matter is experiencing near a black hole, but still far away from the even horizon. They deform the matter very violently, hearing it so much that its normal heat radiation goes to the X-ray wavelengths.

Ah I see. Thank you everyone that responded!

The visible effects we see for black holes are things from well outside the event horizon, where black holes behave as just another gravitational object. Things, i.e. gas, can rotate and swirl around them. Since the black hole can be rotating and the gas being slung around violently, it can emit radiation. If I understand correctly, the jets for supermassive black holes can extend out to sizes comparative to the containing galaxy’s diameter.

Here’s a nice simulation showing this in action (article in description): https://youtu.be/g1aW8TDOm4A

The YouTube channel Kurzgesagt also has some pretty good illustrations and animations.

There's a difference between objects falling into the black hole versus material accreting on the black hole's horizon that can generate high energy beams.

FWIW, I asked my physicist friend this question one time. He said while an outside observer would never see a "massless test particle" enter the event horizon due to time dilation effects, real particles have mass and their own gravitational field, and thus due to complicated stuff they can eventually been seen passing through or otherwise somehow merging with the event horizon.

It is and it isn't true. Light from the falling object will be red-shifted, and eventually you won't be able to see it, but if you could see extremely long wave-length light, and if you could observe it for a really long time, you'd see light from that object asymptotically approach the universe's size as its wavelength, and you'd never see the object go over. But obviously it's not possible for humans to observe extremely long wavelength light, so you'd just see the object disappear when light from it red-shifts beyond the range you can observe.

The object, meanwhile, does fall in from its perspective.

The object falling in has its time dilated to forever - it will never actually experience the "getting there". Outside observers, on the other hand, will observe the "getting there" just as if the black hole were any other large mass.

Or do I have that backwards...

You have that backwards. The person falling into the black hole falls straight towards the singularity as if it was any other massive object, straight through the event horizon without noticing anything change.

The far away observer sees the falling one infinitesimally approach the event horizon, but never cross.

>The person falling into the black hole falls straight towards

I guess you're assuming zero velocity by that person. But if there is velocity, wouldn't the fall not be straight towards but in an ever shrinking/decaying orbit trajectory?

Terrific, thank you!

I should have remembered the film Interstellar, where an observer on a spacecraft orbiting a massive planet (itself orbiting a black hole) feels decades pass whereas the landing party to the massive planet experience about an hour go by.

Even wording this sentence is difficult! I'm reminded of the Persian word for time, which literally means "the thing that passes".

This ”never cross” statement bends my mind. Doesn’t it also mean that if we are observers, observing a black hole, we should not see an actual blackness as we should only see things that are slowly falling into the hole? Regardless of how much time that has been spent from the beginning of time? I mean the event horizon is the boundary but that never happen?

Because of time dilation, light emitted (or reflected off of) objects very near the event horizon end up getting spaced out over (almost infinite) amounts of time.

For example, lets say you dropped a beacon that flashes every second into a black hole. As it approached the event horizon, you'd see the flashes only happen every 2 seconds, 4 seconds, minute, hour, decade, etc. Meanwhile, the length of those flashes are getting longer at the same rate, while producing the same number of photons, so the light gets dimmer and dimmer.

Another factor, that other things are falling into the whole, wouldn’t that mean that the event horizon, relatively, gets closer to an earlier object? Meaning an object may reach the event horizon faster than it would originally or is that constant relatively where the object exist in its descend?

The light is increasingly redshifted, so for practical purposes it disappears from view quite quickly.

The more sensitive the instrument, the longer you can observe, and this doesn't really have a limit - as sensitivity approaches infinity, so does the length of time you could continue to observe the object.

But for practical purposes, we would not see a black hole as some sort of weird psuedo-magnet with all sorts of junk stuck to the edge of the event horizon.

Backwards

Thank you!

Yes, the outside observers can see the item falling into the blackhole while the object experiences more and more time dilation.

If you were falling into a wormhole, you would die of old age before getting there while outside observers would see you fall in quickly.

You would be ripped apart instantaneously while everyone outside of the black hole would see the light you emit as you’re crossing the event horizon frozen in time. It’s an optical effect, nothing magical is happening to you as you fall into the enormous mass

Like the comment you were responding to, you have that backward.

You are correct, and it means black holes can never actually form, because it would take an infinite amount of time for them to form.

> since we see effects of black holes all the time.

We do not, we see super massive objects, or black holes in progress, but no actual black holes.

>You are correct, and it means black holes can never actually form, because it would take an infinite amount of time for them to form.

This is incorrect. They necessarily do not have an event horizon that light cannot escape until they are a black hole, so as they have finished forming into one by the time we can no longer observe past the event horizon. We can also still witness the black hole growing even after that point. [1]

1. https://www.forbes.com/sites/startswithabang/2020/01/11/ask-...

I appreciate you finding me this link, but I have MAJOR issues with the explanation.

It basically say that yes, it will take an infinite amount of time, but because the mass is able to arrive at the black hole before it becomes a black hole, it can first arrive at the black hole, and then after that the event horizon will grow to encompass the new mass.

I'm sorry, but that's just ..... I don't even know how to respond. The mass arriving and the black hole changing mass happen at the exact same time, as the mass arrives, the time dilation of the pending black hole increases, and the mass never actually arrives. These things don't happen sequentially, they happen simultaneously.

There's a couple of things here.

1) Again, it cannot have this event horizon until it becomes a black hole. That is one of the defining features of a black hole. We will be able to see photons escaping through the collapse period until it is a black hole, and once photons can't escape, it is already a black hole.

2) Time does not flow universally with a single reference frame. It appearing to take infinitely long for something to fall into the black hole from our point of view does not mean that it does so for the thing falling into the black hole or for the black hole itself. Time flows normally for the observer, and if they are falling into, say, a supermassive black hole with limited tidal forces, and in a spaceship that can protect from the radiation, etc. from the accretion disk and everything else, they will not notice anything particularly different about the low of time as they fall.

In fact, for black holes of sufficient size and with sufficient charge or rotational velocity, there's actually a second event horizon past the first that could even potentially support stable orbits, even those of planets or entire solar systems. It's likely only a theoretical thing - we don't know a mechanism that would generate enough rotational velocity or charge for a black hole large enough for there to be enough room to push this second event horizon out far enough from the singularity to make this practical. But time flows differently for both parties, and the increase in mass in the black hole is immediate for the black hole itself, as is the increase in the event horizon's radius, as it would be for anything falling into it.

To your point #2 people say this a lot, but it's really not relevant. Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist.

Keep in mind that from the POV of the infalling object they experience the entire lifetime of the universe! The two POV's are complimentary - just like it takes until the end of time to fall in (from the POV of the infalling object), it also means I never see the black hole form.

i.e. from both POV's the black hole only forms at the end of time (which of course is never, since time never ends).

You've got a whole lot of misconceptions here.

>Because from my POV here on Earth, just like I can't see the final object fall in a make a black hole, the same way from my POV the black hole also doesn't exist.

Again, until there is an event horizon it is not a black hole. Once it has the event horizon, it is a black hole. Once it at the point that you are concerned about this, it is already a black hole. If you are in a situation where your (misunderstood) scenario is occurring, it is already a black hole.

(I am speaking purely of the gravitational event horizon here, not a causality event horizon a la the observable universe, etc.)

>just like it takes until the end of time to fall in (from the POV of the infalling object)

It does not take until the end of time to fall in. If you were to be launched into a black hole that lacked strong enough tidal forces to spaghettify you, you would go past the event horizon at basically the same speed you were going right before you crossed. If you are going straight towards the center of the black hole, you will be accelerating under the gravitational forces.

>it also means I never see the black hole form.

Again, even if what you were saying is true (and it isn't), by definition the black hole has already formed when it collapses into a singularity (or something closely approximating our understanding of the singularity) and gains this event horizon. Not one atom or quark or any other type of particle more needs to fall in past this point for the black hole to have formed, because it already has. If it somehow formed in some sort of theoretical vacuum where even virtual particles do not pop into existence and never even had a particle or anti-particle appear and fall in, it would still be a fully formed black hole.

>which of course is never, since time never ends

Not really related to the current discussion, but we don't actually know if this is the case or not, either from a philosophical or hard science perspective. There are plenty of cosmological models where time ends, or the emergent property we call time stops being an emerging property because of some other reason, etc.

https://en.wikipedia.org/wiki/Spaghettification

I think spaghettification is my favorite word, maybe it's tied with defenestrate.

So an observer near the black hole would see an eternally accumulating number of objects falling towards it, but crawling to a halt near the event horizon?

It depends on the sensitivity of the instruments. For human eyes looking out the window of a spaceship, they would be redshifted away to invisibility pretty quickly.

And the light getting increasingly red shifted until you can't really see it anymore.

I see. Another way to think of "redshift" is "lower energy", so these things will disappear from sight another way.

I tried to perform a frequency domain analysis of the recorded signal but it's returning HTTP 419 Never Gonna Give You Up

The big untouched mystery is how these things collimate the beam so exactly.

In order for all the mass to end up going in exactly one direction, so focused, something would have to get them started off that way. Any sort of thermal phenomenon would need a parabolic reflector/nozzle.

Currently favored is some sort of electromagnetic process that works like a particle accelerator, applying a linear electric field to highly-ionized nuclei over thousands or millions of km.

The "geysers" coming out of Enceladus would likewise need parabolic nozzles to stay collimated, so must be similarly electromagnetic. Unfortunately the notion was first promoted by reviled "electric universe" enthusiasts, so astrophysicists need to file the serial numbers off before they can acknowledge it.

Could gravitational forces between particles in a beam tighten a beam as it travels?

Yes. Curiously, this would work even for a sufficiently intense beam of light. It is called "self-focusing", and has been proposed for use in an interstellar transport network.

Your vehicles would need not to be ripped apart to individual nucleons by the intensity of the beam.

> jet speed is 99.99% the speed of light

Does that mean a wave of particles is coming at us right behind the light flash?

That was my first thought too. But even at that speed, we have quite a bit of time. Since the particles are 0.01% slower than the light that just reached us, the particles would arrive in: 8,500,000,000 light years away * 0.01% speed of light = 850,000 years. Humanity will be unrecognizable by that point.

Wouldn't the galatic rotation mean the earth will be somewhere far away when the jet travels that far?

On the flip side that also means that we might flow into a burst travelling through space without any warning (?)

That got me wondering how far we'd move - if my maths is correct then in 850,000 years time our solar system will have travelled 652 light years around the galactic core (230 km/sec * 850,000 years)!

How wide is the beam? (given how far it started) Light-years?

Is it still dangerous at this point? (If its energy is spread over a giant area radius billions light-years)

Yes, that and both galaxies careening through space on different trajectories.

A couple more 9's changes that drastically though. Maybe someone just truncated at 2 decimal places?

If it is 8.5 billion light years away and was traveling at the speed of light (100% instead of 99.99%) wouldn't it take 8.5 billion light years? Wonder how you got to the 850K years figure.

> wouldn't it take 8.5 billion [years]?

Yes, if you are assuming the jet was emitted right now. But the jet was emitted roughly 8.5 billion years ago. The light in front of the jet has already reached us. If the jet were also travelling at the speed of light we'd be dead right now. But luckily it's travelling slower than light so that's why we have 850k more years before the jet reaches us.

Would we actually? If so, doesn't this imply that the probability of earth just having been destroyed by one of these things was roughly a coin flip, and therefore gives us a (much higher) rough estimate of how likely such an event might be?

> If the jet were also travelling at the speed of light we'd be dead right now

Does that mean, once the jet reaches us 850K years from now, we can say that will be a mass extinction event, or even the end of life on Earth? Compared to a billion years from now when the Sun's luminosity increases.

No. The matter in these jets isn't like a spaceship where the matter is all connected together. It's largely individual plasma particles - over billions of light years they'll run into other particles, be deflected, slow down, etc. There IS friction in space.

Matter decay will have significant impact on the mass of matter ejected by the jet, as well, particularly over billions of years. As it decays into a lower energy state, mass will be turned into photons, and less and less of it will be left to impact.

Plus, we won't be in the same spot in 850k years anyway. The solar system is moving around the galaxy, and the galaxy is moving around the universe, and space in the universe is expanding.

Interesting, thank you very much.

They're saying the difference between the time the light gets here and the particles 'only' going 99.9% of C is 850K years back of the napkin.

By his logic, an object moving at 0% of the speed of light would arrive instantly.

An object moving 0% slower than the speed of light would arrive instantly after the light arrives, yes.

When doing such a calculation, would you need to take into account the fact that space is expanding while the particles are traveling? (And will have expanded a bit more in the time it takes for the particles to reach us than in the time it took for the light to reach us.)

Not necessarily. Particles will all be charged plasma and it is possible that those will be deflected by magnetic fields. But I am not astrophysicist so you would want to check on it.

Also, in contrast with the flash where all light has the same speed, the particles will have different speed so it will all be smeared in time (read -- much smaller in amplitude and hard to detect) and arriving much later than the flash.

Then from the point of view of observer on Earth surface, charged particles will not be coming exactly from the source but at a bit of an angle (due to magnetic fields present). Again, I have no knowledge about the magnitude of the effect and I also suspect that the people who know this shit have some way to account for it...

No. The light from these jets travels many many magnitudes farther than the actual material. You wouldn't want to be within a few million light years of it but these particles have mass and will be slowed by all of the matter they interact with in space. The vacuum of space still has roughly an atom per cubic centimeter, which really adds up over the distances we're talking about here.

Edit: Left out a fairly important word. few million light years*

"From a rough calculation, the flash appeared to give off more light than 1,000 trillion suns."

Can any space geeks chime in on this one?

Does this mean the emission of light from the sun at a single point in time x 10^15? My brain pretty much divides by zero even trying to comprehend such a large number and I'm just trying to grasp the relationship of the emitted light to our sun.

As others have said, its not quite the same as the Sun's output, but it is still an incredible amount of light.

I have studied blazars fairly extensively in the past and you are right that the brain cant really fathom the 'real world' appearance of these things. I resort to just thinking in terms of number of photons and avoid thinking about the rest, as it tends to result in a lot of existential dread and drinking.

One way of thinking about this is in terms of incident sunlight at Earth's orbit.

A trillion is a rather large number. Some quick maths says that 1,000 trillion cm^2 is 100,000 km^2, or a region roughly 315 km on a side (195 miles), or a circle with a radius of about 126 km (77 mi).

Alternatively, if you consider sunlight falling on a patch of ground for one second, the amount reaching it over 1 trillion seconds would take about 32,000 years.

So think in terms of a very large magnifying glass (I'd suggest considering a Fresnel lens for economy's sake), or a very long-term accumulator.

> My brain pretty much divides by zero even trying to comprehend such a large number

I've tried using this line in the wrong company that wasn't math oriented, and it fell flat.

It's also amusing your use of this phrase, as in a lot of the astronomy circles I've seen/read, there's a joke that black holes are where god divided by zero. So it felt very apropos to me in this context too.

That would be assuming the same amount of light was emitted in all directions. But we have no indication that that was the case.

I roughly translate this to 10^15 x more photons per square meter of surface area at some standard distance.

Whoah, this goes way beyond Sarah Connor: "Anybody not wearing two million sunblock is gonna have a real bad day".

Is this going to annihilate us? I didn't see them mention any safety risks, but it sounds similar to a quasar to me (a non-astronomer), and I think if one of those is pointing at us, we're toast. If they just detected the light, and the matter is going 99.9% of the speed of light, does that mean we're toast tomorrow? Next week? Next year?

Well it seems like we've detected 3 other jets pointed straight at us as the black hole devoured a star so it seems like a very common event on a geological time scale. The fact that we managed to evolve and are still here is a decent sign.

>The team says the black hole's jet may be pointing directly toward Earth, making the signal appear brighter than if the jet were pointing in any other direction. The effect is "Doppler boosting" and is similar to the amped-up sound of a passing siren.

>AT 2022cmc is the fourth Doppler-boosted TDE ever detected and the first such event that has been observed since 2011.

Also, I believe that as the universe's volume expands, the probability and intensity of being in the direct path of any particular such jet goes down. Then again, the frequency of these events may (or may not) be increasing at a rate that more than counteracts that. (I'm just speculating here, I'm not a cosmologist!)

Most of the threat from relativistic jets is from within ones own galaxy (and at worst, its local group). So, yes as the universe expands the risk from the latter should decrease, the risk from the former wouldn't really change due to expansion. The risk probably does still come down, but more due to age as larger clouds of gas get used up and spread around by supernovae, preventing enough mass from gathering for the things that produce relativistic jets.

One possible answer to the Fermi paradox is that we're early because the universe may have only recently gotten calm enough for life to survive long enough to develop intelligence.

As far as I understand it, gravitational lensing would affect the trajectory of particles travelling different speeds differently. So it would seem entirely possible that the matter wouldn't even be pointed at us. That assumes that either is being significantly affected by gravity of course.

Also bear in mind that though the light of 1000 trillion suns has been pointed at us, it's not like we have a second sun in the sky right now. It's really, really far away.

It's 8 billion light years away. We'll be fine.

If the matter is trailing at 99.99% the speed of light as reported, it gives us 800k years.

The matter was traveling at 99.99% the speed of light in the jet. While we generally consider space to be a friction-less vacuum for something like a spaceship, that isn't true for things like a stream of particles traveling across the universe. Even if the Earth stood still in this exact position for another 800,000 years (which it won't, since our galaxy is not stationary, nor is the solar system, and there is of course the expansion of space as well), very little of the physical matter from this jet would hit us.

Wouldn’t it give us way more than that? If it were traveling at 100% the speed of light it would take 8 billion years right?

The light has already taken 8 billion years to get here. The particles have also been traveling for that time and are only 800,000 years away now.

“Hey Siri, set a reminder for…”

For now!

I'd believe the small percent of a percent of the sky we're in for it to be pointing at us is still a large swath of trillons of miles.

And 850k years from now - our galaxy would have moved from it's location anyways. Some other galaxy will probably waltz into it.

Very interesting. Does this imply (assuming these jets have been occurring for a very very long time) that we'd be able to see the consequences of other jets in other galaxies/planets? Said another way, have we ever observed something that could actually have been "... some other galaxy waltzing into it"?

One of Earth's past mass extinction events is hypothesized to have maybe been caused by a gamma ray burst[0]. I don't know enough to speculate whether it could have been caused by one of these jets instead.

[0] https://en.wikipedia.org/wiki/Late_Ordovician_mass_extinctio...

If it is going to, would you even want to know?

Wonder if this burst could have been seen with the naked eye? They mentioned it was visible on multiple spectrums.

I am also curious about this. I would sometimes look up while walking my dog and wonder if by chance I woukd see a sudden addition to the night sky.

How wide is this jet here? Does it cover the entire Milky Way?

8.5 billion light years away, vs. ~100,000 light years across. To cover the whole galaxy, from a point source it would need to spread out just 1 part in 100,000. So, probably.

Yes, technically our galaxy is a lot bigger than 100,000 ly, but the part somebody looking out from Andromeda could see isn't.

Kurzgesagt just did a vid on black holes and how close they have to be before we're f'd.

The Most Extreme Explosion in the Universe

https://www.youtube.com/watch?v=q4DF3j4saCE

> 8.5 billion lights years away—more than halfway across the universe

Why is it halfway across? The universe's diameter is 93 billion ly. Shouldn't 8.5 billion be more like "ten percent across"?

universe is a relative word, and typically treats us at being at the center (which in the whole of reality is somewhat unlikely). So it only describes that part of reality observable by us. 8,5 bn ly refers to roughly half distance to all of the observable events in that observable reality at the time these events occured. Since 3D space presumably expands, it would now take much more time for any event in our observable "universe" to reach from one end of the observation limit to the other...

by the way - if you want to go down further that rabbit hole a good place to start is to search for "levels of multiverse"

(I'm not an astrophysicist). They possibly are referring to the initial age of the universe times the speed of light (13.8 billion light-years), as if it was static.

Like you infer, "[...] stuff is everywhere, light goes at c, stars and galaxies move, and the Universe is expanding."

https://www.forbes.com/sites/startswithabang/2018/02/23/if-t...

I think it's more likely they got it wrong and are referring to what they assume the size of the universe is. It's hard to grasp why the observable universe is 92 billion ly in diameter

What is the probability of something so far away pointing straight towards Earth? What is the angle in which this phenomenon spreads out into space?

paper: https://arxiv.org/pdf/2211.16537.pdf

Here’s the paper by the discovery team: https://arxiv.org/abs/2211.16530

> Typically, such bright flashes in the sky are gamma-ray bursts—extreme jets of X-ray emissions that spew from the collapse of massive stars.

Is that right? Surely gamma ray bursts are gamma rays, not X-rays. At least, shouldn't it say "extreme bursts of X-rays and gamma rays [...]"?

GRBs start, as their name suggest, as a burst of gamma rays, but have long tails of emiting of x-rays and other lower energy photons that we're more likely to notice.

“Pointing directly toward earth” …hmmm. In what possible frame of reference could anything be pointed directly toward earth for longer than a moment in space and time? We are traveling through space and time in multiple frames of reference at a tremendous rate. This confuses me.

We are incredibly far away from objects like this, so the apparent movement is negligible.

haven't you got this backwards? the further the distance the smaller movement an object would need to not be in the trajectory?

No?

Want to point out how incredibly good the website phys.org is.

I was first introduced to it over 15 years ago and remember visiting it using dial-up internet from Pakistan as a teenager to learn about the latest developments in physics.

Gem of a resource that is still going strong.

When they say "pointing straight toward Earth", is that hyperbole? Or are they actually saying that by pure random chance, out of all the possible directions this thing could have taken, it just happens to be pointed directly at earth?

The beam is surely wider than the planet so there's a large range of "straight toward"

It should be at least broad enough to compensate for some movement of the earth, considering it was observed for at least some days

If I point a flashlight directly at you, that's different from me pointing the flashlight at the person standing next to you. Even though in both cases the beam will light you up.

But that becomes effectively the same thing if the flashlight is being pointed in your direction from 10km away and it's reasonable to just describe it as pointing at you. Coming from 8 billion ly away, the beam is probably wide enough that it would appear to be pointed at the Milky Way in general.

Yeah this is pretty much the case.

The important thing is that the light from the beam is sufficicently bright that it is not possible to resolve the surrounding region of space to see more detail.

It's 8 billion light years away, even if the beam was very focused by the time it reached us it is probably tens of thousands of lightyears wide.

I suppose the metric expansion of space over this scale would also diffuse the light

I tried to find a calculator (you can find ones for "laser over meters") that would support supernovas over lightyears and came up short.

But there are a lot of black holes yes? Surely some of them will point towards us.

Depends on the width of the beam. If it's as wide as a laser pointer, the odds of it hitting anything are infinitesimal. When something's a light year away, changing the bearing of the laser by a degree will cause you to miss it by hundreds of thousands of kilometers. Or to rephrase, to hit something a light year away you'll have to get the heading accurate to many decimal points. (Exercise left to the reader, it's high school trigonometry, but I'm rather lazy).

It's also a statistical question that involves how many black holes there are. Do you have a strong sense of that number, because I sure don't?

Quick search says there are a very large amount of black holes but maybe not so many super-massive that produce these beams of light so eh, who knows.

https://telescope.live/sites/default/files/styles/photo_w102...

very bright ^^

https://telescope.live/blog/transient-flash-identified-dista...

> 8.5 billion lights years away—more than halfway across the universe

That was the first number I was looking for.

Not a threat to earth. It's not even in our galaxy.

I don't know, its pretty bright. Maybe this periodic flash-fry is what created life on earth!

This sort of thing really makes me feel uncomfortable.

What are the odds of this hitting us, during our lifetime with the technology to record it.

Seems far fetched.

If you could controll the direction of a black hole, you could use it to "disinfect" the neighbourhood or send messages.

It's 8.5 billion light years away. It would be like aiming a water hose at Mars from low Earth orbit.

I've wondered whether or not black holes or cosmic masers might be used for very-long-range communications or signalling.

so given this tool we would either murder or flirt

can there be anything so human ?

How many years advance notice would we have before we knew that such an event was our fate? To be eaten by a black hole…

> From a rough calculation, the flash appeared to give off more light than 1,000 trillion suns

Not a single astronomical photgraph

In all likelihood the observation and analysis are based on sensing data rather than images.

If you could see something, it would be a dot next to a smudge --- the jet and its adjacent galaxy.

Overexposure issues...

it's the focused beam of tortured souls escaping the event horizon that worries me.

Why do you think they were tortured? Maybe they were ejected for heavy drinking while waiting in a queue to a paradise. We do not know what is inside of a black hole, but funny ways of matter around a black hole seems like a result of drunkinness. How one can miss black hole while falling into it? Try to miss Earth while falling on it. No amount of gin seem to be enough. But they somehow managed to miss a black hole which is much heavier than Earth. They used a tremendous amount of gin to get into the right state of a mind. No wonder they were stripped of their right to a paradise and ejected from a queue.

maybe? could be? possibly? Highly doubtful and impossible to verify

ChatGPT has made contact

* blackholes are not confirmed science. It is theory and little evidence supports the theory. * Math is not reality, it is a description of reality that should require evidence * this could be many other things including plasma

Little evidence? We've got pictures of them a this point, friend. While we are not entirely sure on all of the specifics, and some things, such as the singularity, are likely a bit different than our current theories suggest, there's mountains of evidence that support the existence of black holes, or at the very least, something that is very very very very very very very similar to them on the macro level.

or at least something that we have named “black hole” when some light follows a specific pattern after traveling through space for billions of years, no reason to assume that this is how it looked when it originally departed

Hmm. If an alien race a million years older than humans eventually figured out how to make synthetic wormholes on demand for FTL when no other method existed, can we theorize what the endpoint might look like?

(this is a "fun" but not kidding question)

One idea is that they'd be one-directional, with a black hole on one end and a white hole on the other end. But considering that we haven't really seen any evidence of white holes existing, such a thing probably isn't possible.

Other than that, a simple traversable wormhole entrance/exit would just look like a sphere where you see the other side sort of 'mapped' onto the surface.

Oh wow, were the Hollywood versions in Contact and Interstellar vaguely based on that science?

Will have to watch them again this weekend and double-check.

I wouldn't necessarily say they're based on science since I don't really think there's enough concrete science on wormholes to say what they would look like precisely (although Interstellar did put some effort into visual accuracy: https://cerncourier.com/a/building-gargantua/).

My reasoning is that just like a circle is formed on a 2d surface when 'bridging' two parts of it (the pencil through folded paper analogy), a bridge on a 3d surface should have a sphere as the hole (or maybe since it's technically a space-time bridge, it should be a hypersphere, which would still appear as a sphere to us 3d observers). Then, to not tear apart anything going through, it'd need to conserve 'symmetry' (so something that goes in comes out unchanged), so the light would go through unchanged, making it just appear like the view of the other side is mapped to the surface.

Imagine this is the end of a wormhole and it fries any planet at the exit.

The Vogons did tell us about the hyperspace expressway in advance but did we listen?

(I can give you a “short” but not short answer to this)

I personally believe that astronomer buzzwords are even worse than business/sales/tech buzzwords. The idea that they are so confident that something is a “black hole” which is also entirely made up, is laughable. It’s just old light, why assume it represents anything at all? Couldn’t the light have been distorted during the long voyage? Maybe all light looks like “galaxies and black holes” after it travels for a billion years through space.

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