> Prior to this new finding, all the black holes that have been identified have also had a companion star—they are discovered due to their impact on light emitted by their companion star. Without such a companion star, it would be very difficult to see a black hole.
It seems like we think there's many more of these black holes, but we just can't see them
This only covers stellar black holes. (Note that this black hole is believed to be a stellar black hole.) Those statistics could change quickly if you add to it a currently unknown number of primordial black holes that arose around the Big Bang.
If those primordial black holes are mostly on their own, and are both numerous and small, they make a potential candidate for dark matter. They could also be potentially small enough to be evaporating in our current era. This has been suggested as a potential source of a very high energy neutrino that was found in February. See https://www.livescience.com/space/black-holes/evidence-for-s....
(Note that this is just a single observation. We are a very long way from being able to obtain strong experimental evidence for such speculative theories.)
A type-1a supernova peer would produce this effect, leaving only the black hole (or the oversize star that would become it). I don't know any other types where the star is completely destroyed.
Gravity pulls things in by causing space-time to accelerate in a particular direction. In other words we accelerate towards the Earth at 9.8 meters per second per second because that is what space-time itself does. The space-time that is in our frame of reference accelerates down, carrying us with it. The floor pushes up on us, causing us to accelerate up. Balancing things out so that we remain where we are.
A dense mass will cause flat space-time to start falling in. Enough mass, densely enough, will cause it to fall in so fast that not even light can escape. This is a black hole.
However the Big Bang wasn't a flat space-time. The space-time that was the structure of the universe was moving apart extremely quickly. There was more than enough mass around to create a black hole today. But what it did is cause the expansion rate to slow. Not to stop, reverse, and fall back in on itself into a giant black hole.
I don't understand this answer. By GR there is no possible flat space-time around a dense mass no? BC the energy will curve the space-time. Saying that the space-time was expanding very quickly is also describing the shape of the space-time. Isn't it kind of circular to say that big bang doesn't end in a singularity b/c it is curved out? You can still ask why it's curved out with so much energy and whether it is compatible with GR? But I guess the answer if GR was holding near big bang must just be that there's some solution which is compatible with GR with so much energy in a small place which doesn't end in singularity.
> Gravity pulls things in by causing space-time to accelerate in a particular direction.
Ok, how does this sketch work for a low-ellipticity eccentric orbit?
> "The space-time that is in our frame of reference"
Isn't throwing out general covariance (and manifold insubstantivalism) rather a high price for a simplification of Einsteinian gravitation?
> the Big Bang wasn't a flat space-time
Sure, it's a set of events in a region of the whole spacetime. If we take "Big Bang" colloquially enough to include the inflationary epoch, always assuming GR is correct, then at every point in that "Big Bang" region of the whole spacetime there is a small patch -- a subregion -- of exactly flat spacetime. However, these small patches must be small because most choices of initially-close pairs of test objects can only couple to timelike curves that wildly spread in one direction (and focus in the other).
I don't know how to understand your two final sentences: how do you connect the period just before the end of inflation and the expansion history during the radiation and matter epochs?
I don't know enough physics to know whether the parent knows what they are talking about, but there is one piece of math that makes me think they do not.
> at every point in that "Big Bang" region of the whole spacetime there is a small patch -- a subregion -- of exactly flat spacetime
Can explain how you get a non-empty region of exactly flat space time around every point?
Patching together curved things out of not curved things happens all of the time. The Earth looks flat around the point you are standing. I'm worried that just because it looks flat in my city doesn't mean it is actually flat in my city, if I measure carefully.
One of the theories is that the properties of the Higgs Field changed and so the laws of physics changed. And that if they ever change again that we'll likely be dead before we know to be afraid, since the change would propagate through the universe at the speed of light. We wouldn't even see the stars blink out before the molecules in our bodies stopped being the molecules in our bodies.
Except that this answer does not make sense. General Relativity predicts that if you fill flat space-time with matter, it will start to contract due to gravity. It is not uniform density by itself that prevented the early Universe from forming a giant black hole.
In fact one of the proposed cosmological models for our universe is that it has sufficient density to some day reverse its expansion and then fall in on itself into a giant black hole. See https://en.wikipedia.org/wiki/Big_Crunch for more.
My theory with zero study, math, or proper explanation is that this is exactly how the universe operates.
It explodes outward until the explosion energy is cancelled out by gravity, wherein the universe then collapses on itself. The moment in which the last bit of matter and energy is consumed by the massive black hole that forms, it's enough to cause another explosion.
Does anyone else find this...unsettling? Floating around in the void of space, alone, is an almost invisible monster that can gobble planets and stars.
It can't really "gobble" anything any more than a star "gobbles" things that fly into its photosphere or a planet "gobbles" things that crash into it.
Unless you cross its event horizon, its gravity works just like any other celestial object. Maybe at worst it slingshots you off in a different direction.
A mass of 6x to 7x our sun (size of this object) would start messing with solar system orbits well before it got here. Not that that would be much better for us!
> wouldn’t want society to know we were about to collide with a star-sized mass
I may be misunderstanding the distances involved but wouldn't such a collision take centuries if not thousands of years to play out? For the most part it would just look like we had 2 suns, one of which gets a few millimeters bigger (to the naked eye) every year.
I'd wager such an encounter is way more likely to result in any of:
1) the Earth being flung out of the Sun's orbit
2) planetary orbits becoming disrupted such that an encounter with another planet over the coming years or millennia becomes likely,
2.1) which could eventually have the same "flinging away from the Sun" effect,
2.2) or (unlikely, but possible) result in a collision
2.3) or result in the Earth being shredded into asteroids
2.4) or other planets suffering that fate and then showering the Earth with dangerously-large asteroids over a period of decades or centuries until it's nearly, or actually (think: outright crust liquefaction from impacts) lifeless.
than the Earth actually getting swallowed up, by at least an order of magnitude.
IOW, the most-likely "we're all dead" outcomes for us, from a close encounter with a massive rogue anything really, including a black hole, might take years and years to play out.
Fortunately space is really, really, really, really, really, really, REALLY big. The chance of this happening is so infinitesimal we might as well worry about spontaneously transforming into a whale or potted flower manifested a mile above the surface of our planet.
That brings me memories of Cosmos 1999. The moon left Earth's orbit to outer space because explosions, but being slingshoted away because a nearby massive enough object passing by looks like a more possible scenario, not explored enough by sci-fi.
Space: 1999. Do you happen to be french or polish?
In Germany they called it "Mondbasis Alpha". As I child I really liked this series and it's predecessor UFO made by the same team (Gerry and Sylvia Anderson of Thunderbirds fame).
The basic premise of the show that an explosion at a nuclear waste dump could produce enough energy to push the Moon out of the Solar System to wander the galaxy is an interesting product of its time. Concerns over the power of nuclear explosions was high and casual access to knowledge about the plausibility of such a scenario was somewhat limited.
There's a fan driven update called Space: 2099 that improves some of the more dated aspects of the show, including showing the Moon enter some type of portal or wormhole to make suspension of disbelief easier. While the Special Edition releases of Star Wars often suffered from updating certain aspects, especially special effects, the Space: 2099 changes were generally good for the show. Too bad they're unable to fund raise enough and get permission to do the entire series.
Direct interaction isn't needed for havoc. A supermassive object sweeping by the Solar System could destabilize Jovian orbits. In the Nice model, Neptune flung Kuiper belt asteroids sunward, gifting the inner planets with a late heavy bombardment.
Rogue gas giants, brown dwarfs accelerated to relativistic speeds, giant asteroids approaching from the Sun's direction, Carrington Events, an ill-directed gamma ray, etc. So many ways life on Earth can see its 250 million remaining years cut short, and those are only a few of the cosmic threats we can imagine.
A black hole with a Schwarzschild radius of 20 km would weigh about 6.8 Solar masses. It wouldn't even need to get super close to affect the Solar System.
No more unsettling than space in general is. It’s pretty hostile to life. We’re not just making turns around the orbital racetrack setup around the Sun, we’re also flying through space following the gravitational trail of the Sun as it races forward without a destination.
I was playing with Universe Sandbox over the weekend trying to figure out how to terraform Venus. Changing its axial rotation period to a day to match the Earth while I screwed around with its chemistry was enough to cause Europa and some of the other famous moons of Jupiter and Saturn as well as Charon to yeet themselves outside of the solar system within about 10 or 20 years of simulated time.
Why would changing the rotation speed of Venus have any noticeable effect on the outer planets? That sounds more like a limitation of the model than anything else. Especially over such a short time! 20 years is nothing to the orbit of Charon.
Probably, but if a Venus-sized mass showed up in the inner solar system because the Sun just picked it up along the way, it might not be instant death but we’re probably in for a rough time. It doesn’t have to be a black hole that does us in, it could be something much smaller that still strips the Moon away or causes Earth to readjust its own position in a way we, as in life, but also maybe we as in humans or we as in mammals just don’t like very much in a very short amount of time temporally speaking, and we couldn’t do anything about it anymore than we could do anything about a black hole because we’re just not the captains of this ship. We’re just some homegrown stowaways.
But for what it’s worth, it’s also just so incredibly unlikely it’s not a scenario worth thinking about either, and thinking about it too much just invites existential dread.
I don't. If the sun were replaced by a black hole of equal mass next Tuesday at noon, the only thing we would notice is that it suddenly got very dark and very cold. We would continue orbiting the thing while freezing to death over the next few days.
The size of the black hole described in the paper is ~ 20 km, so it is tiny. Even we have millions of such objects (and most likely we do), the chance of hitting something, given the enormous size of the galaxy is negligible.
The black hole in the paper is also ~7 solar masses. If that passed between the Earth and the Moon it would rip apart the earth from just the tidal forces.
No, not me anyway. we are all floating (falling) in the (nigh) void of space (equally) alone ... which is great protection from all the monsters everywhere!
Deliberately hitting things in space is hard, accidentally, more-so.
Consider the chance of our sun getting whacked when the entire Andromeda galaxy gets here ... billions or more likely trillions to one. The chance of a single mass in our own galaxy getting us should be less than that.
edit: as far as I know the only difference between getting gobbled by a black hole v.s. anything else is our atoms won't get to continue their evolution into larger atoms in this universe. (or maybe see it as our atoms get to complete their evolution in this universe)
There are many theoretical astronomical risks. For example, if we happened to come into the path of a relatively nearby gamma-ray burst, it could eliminate all life. Given that life has existed on the earth for quite some time, the 'Lindy effect' suggests that the sum of these presumably-constant risks is small. We are much more likely to become extinct due to an anthropogenic cause.
It would be nice to get a rigorous estimate on how big and nearby a black hole could be before we'd notice it with routine sky surveys or orbital deviations. A 6-solar-mass black hole only has a radius of around 18km or 11 miles. How often will one pass in front of a star precisely enough for OGLE and MOA to detect it, as they did with this one?
Apparently the Roman Space Telescope will be great at detecting these, if it doesn't get cancelled.
I'm trying to picture intersecting paths though. Does a faster moving black hole cause more or less damage to a target?
Imagine a black hole on the quite small end, intersecting the core of a planet. Unlike regular matter, it can't really produce bow shock through collisions, right? All the target matter in the direct path just "falls in" and in elastically reduces the black hole momentum a tiny bit?
Some matter outside the direct path could be accelerated towards the black hole but slingshot behind it, rather than into it. So this material could produce an impressive wake, with material spraying outward from the collision path and interacting with the remainder of the target.
But, all this visible chaos comes from gravity rather than more direct kinetic interactions, right? If the black hole is moving faster, doesn't the target's material gets less gravitational acceleration as it spends less time in the near field? So, if the blackhole is moving very fast, does it bore a smaller hole and have less interaction with the target? Or do other effects of relativity make this more convoluted to think about?
I'm imagining a cylindrical plug of a planet "instantaneously" disappearing, and then the remainder of the planet collapsing inward to fill the void, bouncing off itself, and ringing like a bell.
> Does a faster moving black hole cause more or less damage to a target?
When a black hole accretes matter, the matter can create tremendous radiation before it crosses the event horizon due to the atoms experiencing many effects such as rapid nuclear fusion and becoming new forms of matter such as neutronium. The precise amount of energy released depends on spin, charge, and size of the black hole, and the speed at which the matter approaches the black hole.
If a tiny black hole (Let's say 10cm across) ripped through the earth at significant speed it would be like the center of the planet momentarily became the center of a star and (hand waving a bunch of assumptions) the total energy could easily be greater than the gravitational binding energy of the planet. The planet would explode.
They makeup much of the stylish universe in the cosmos ;-)
Just kidding, I know you meant rogue.
I would assume we'd see a lot of more tricks of light bending if they did. Light lensing was used to confirm relativity by looking for multiple super novae signatures from the same event, which passed by large black holes on their way here!
Depends on the size, position, and number of black holes, right? We see lensing currently because of super massive black holes that we know about. But if there's a bunch that are basically as massive as our sun (or less) then we are dealing with event horizons ~3km or less. It'd be pretty hard to spot those as the diffraction would be rounding errors.
This would certainly be some of it but the awkward fact is that we've positively identified so very little of the matter that makes the universe the shape that it appears to us to be that we could double the known matter in the universe with black holes and we'd still only be a 10th of the way there.
However if we could eliminate the false signals from invisible (singularity) matter I am hopeful that will give us a clearer idea of whatever the rest is.
I can't remember who I heard talk about this, but scientists have considered this. I think there was a good reason for why it doesn't seem to match observations.
If a significant portion of dark matter was made of these we would see a lot more gravitational lens distorions of distant objectes. There are further hard limits on how much baryonic dark matter there can be from big bang nuceleo synthesis. I think that would also put limits on contributions from lone black hole contribution.
It seems like we think there's many more of these black holes, but we just can't see them
If those primordial black holes are mostly on their own, and are both numerous and small, they make a potential candidate for dark matter. They could also be potentially small enough to be evaporating in our current era. This has been suggested as a potential source of a very high energy neutrino that was found in February. See https://www.livescience.com/space/black-holes/evidence-for-s....
(Note that this is just a single observation. We are a very long way from being able to obtain strong experimental evidence for such speculative theories.)
Earlier article about first discovery: https://iopscience.iop.org/article/10.3847/1538-4357/ac739e/...
Gravity pulls things in by causing space-time to accelerate in a particular direction. In other words we accelerate towards the Earth at 9.8 meters per second per second because that is what space-time itself does. The space-time that is in our frame of reference accelerates down, carrying us with it. The floor pushes up on us, causing us to accelerate up. Balancing things out so that we remain where we are.
A dense mass will cause flat space-time to start falling in. Enough mass, densely enough, will cause it to fall in so fast that not even light can escape. This is a black hole.
However the Big Bang wasn't a flat space-time. The space-time that was the structure of the universe was moving apart extremely quickly. There was more than enough mass around to create a black hole today. But what it did is cause the expansion rate to slow. Not to stop, reverse, and fall back in on itself into a giant black hole.
Ok, how does this sketch work for a low-ellipticity eccentric orbit?
> "The space-time that is in our frame of reference"
Isn't throwing out general covariance (and manifold insubstantivalism) rather a high price for a simplification of Einsteinian gravitation?
> the Big Bang wasn't a flat space-time
Sure, it's a set of events in a region of the whole spacetime. If we take "Big Bang" colloquially enough to include the inflationary epoch, always assuming GR is correct, then at every point in that "Big Bang" region of the whole spacetime there is a small patch -- a subregion -- of exactly flat spacetime. However, these small patches must be small because most choices of initially-close pairs of test objects can only couple to timelike curves that wildly spread in one direction (and focus in the other).
I don't know how to understand your two final sentences: how do you connect the period just before the end of inflation and the expansion history during the radiation and matter epochs?
> at every point in that "Big Bang" region of the whole spacetime there is a small patch -- a subregion -- of exactly flat spacetime
Can explain how you get a non-empty region of exactly flat space time around every point?
Patching together curved things out of not curved things happens all of the time. The Earth looks flat around the point you are standing. I'm worried that just because it looks flat in my city doesn't mean it is actually flat in my city, if I measure carefully.
--Douglas Adams
In fact one of the proposed cosmological models for our universe is that it has sufficient density to some day reverse its expansion and then fall in on itself into a giant black hole. See https://en.wikipedia.org/wiki/Big_Crunch for more.
It explodes outward until the explosion energy is cancelled out by gravity, wherein the universe then collapses on itself. The moment in which the last bit of matter and energy is consumed by the massive black hole that forms, it's enough to cause another explosion.
Unless you cross its event horizon, its gravity works just like any other celestial object. Maybe at worst it slingshots you off in a different direction.
A small, lone black hole could be on an intersecting trajectory with us within a few years and we’d be completely oblivious.
Is this what would happen if we got slurped into a black hole? I was hoping for something more exciting …
I’d probably welcome the quicker demise tbh
I may be misunderstanding the distances involved but wouldn't such a collision take centuries if not thousands of years to play out? For the most part it would just look like we had 2 suns, one of which gets a few millimeters bigger (to the naked eye) every year.
With all that said, maybe it's better off if we were completely oblivious.
even that would be a slow death I suppose. Don’t think the Earth would just vanish instantly.
1) the Earth being flung out of the Sun's orbit
2) planetary orbits becoming disrupted such that an encounter with another planet over the coming years or millennia becomes likely,
2.1) which could eventually have the same "flinging away from the Sun" effect,
2.2) or (unlikely, but possible) result in a collision
2.3) or result in the Earth being shredded into asteroids
2.4) or other planets suffering that fate and then showering the Earth with dangerously-large asteroids over a period of decades or centuries until it's nearly, or actually (think: outright crust liquefaction from impacts) lifeless.
than the Earth actually getting swallowed up, by at least an order of magnitude.
IOW, the most-likely "we're all dead" outcomes for us, from a close encounter with a massive rogue anything really, including a black hole, might take years and years to play out.
Have you seen the Walking Dead?
Space: 1999. Do you happen to be french or polish?
In Germany they called it "Mondbasis Alpha". As I child I really liked this series and it's predecessor UFO made by the same team (Gerry and Sylvia Anderson of Thunderbirds fame).
There's a fan driven update called Space: 2099 that improves some of the more dated aspects of the show, including showing the Moon enter some type of portal or wormhole to make suspension of disbelief easier. While the Special Edition releases of Star Wars often suffered from updating certain aspects, especially special effects, the Space: 2099 changes were generally good for the show. Too bad they're unable to fund raise enough and get permission to do the entire series.
https://www.youtube.com/watch?v=wPTZaSv9Bxk
Direct interaction isn't needed for havoc. A supermassive object sweeping by the Solar System could destabilize Jovian orbits. In the Nice model, Neptune flung Kuiper belt asteroids sunward, gifting the inner planets with a late heavy bombardment.
Rogue gas giants, brown dwarfs accelerated to relativistic speeds, giant asteroids approaching from the Sun's direction, Carrington Events, an ill-directed gamma ray, etc. So many ways life on Earth can see its 250 million remaining years cut short, and those are only a few of the cosmic threats we can imagine.
A black hole with a Schwarzschild radius of 20 km would weigh about 6.8 Solar masses. It wouldn't even need to get super close to affect the Solar System.
https://en.wikipedia.org/wiki/Pangaea_Proxima
Life might very well exist on earth even through those conditions, but not to the extent we have today.
I was playing with Universe Sandbox over the weekend trying to figure out how to terraform Venus. Changing its axial rotation period to a day to match the Earth while I screwed around with its chemistry was enough to cause Europa and some of the other famous moons of Jupiter and Saturn as well as Charon to yeet themselves outside of the solar system within about 10 or 20 years of simulated time.
But for what it’s worth, it’s also just so incredibly unlikely it’s not a scenario worth thinking about either, and thinking about it too much just invites existential dread.
Deliberately hitting things in space is hard, accidentally, more-so.
Consider the chance of our sun getting whacked when the entire Andromeda galaxy gets here ... billions or more likely trillions to one. The chance of a single mass in our own galaxy getting us should be less than that.
edit: as far as I know the only difference between getting gobbled by a black hole v.s. anything else is our atoms won't get to continue their evolution into larger atoms in this universe. (or maybe see it as our atoms get to complete their evolution in this universe)
Apparently the Roman Space Telescope will be great at detecting these, if it doesn't get cancelled.
Imagine a black hole on the quite small end, intersecting the core of a planet. Unlike regular matter, it can't really produce bow shock through collisions, right? All the target matter in the direct path just "falls in" and in elastically reduces the black hole momentum a tiny bit?
Some matter outside the direct path could be accelerated towards the black hole but slingshot behind it, rather than into it. So this material could produce an impressive wake, with material spraying outward from the collision path and interacting with the remainder of the target.
But, all this visible chaos comes from gravity rather than more direct kinetic interactions, right? If the black hole is moving faster, doesn't the target's material gets less gravitational acceleration as it spends less time in the near field? So, if the blackhole is moving very fast, does it bore a smaller hole and have less interaction with the target? Or do other effects of relativity make this more convoluted to think about?
I'm imagining a cylindrical plug of a planet "instantaneously" disappearing, and then the remainder of the planet collapsing inward to fill the void, bouncing off itself, and ringing like a bell.
When a black hole accretes matter, the matter can create tremendous radiation before it crosses the event horizon due to the atoms experiencing many effects such as rapid nuclear fusion and becoming new forms of matter such as neutronium. The precise amount of energy released depends on spin, charge, and size of the black hole, and the speed at which the matter approaches the black hole.
If a tiny black hole (Let's say 10cm across) ripped through the earth at significant speed it would be like the center of the planet momentarily became the center of a star and (hand waving a bunch of assumptions) the total energy could easily be greater than the gravitational binding energy of the planet. The planet would explode.
They makeup much of the stylish universe in the cosmos ;-)
Just kidding, I know you meant rogue.
I would assume we'd see a lot of more tricks of light bending if they did. Light lensing was used to confirm relativity by looking for multiple super novae signatures from the same event, which passed by large black holes on their way here!
However if we could eliminate the false signals from invisible (singularity) matter I am hopeful that will give us a clearer idea of whatever the rest is.
Found a couple of videos on it too
https://youtu.be/qy8MdewY_TY
https://youtu.be/d0wV5frSb6s