Astronomers confirm the existence of a lone black hole
62 comments
·April 21, 2025OsrsNeedsf2P
adastra22
Lone stars are actually the exception, so not radically more as you might think. But there are also binary black holes.
btilly
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.)
chasil
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.
wglb
Astrophysical Journal article: https://iopscience.iop.org/article/10.3847/1538-4357/adbe6e
Earlier article about first discovery: https://iopscience.iop.org/article/10.3847/1538-4357/ac739e/...
mirekrusin
What I don't understand is how big bang could exist if such relatively "small" mass concentration creates black holes?
btilly
Excellent question.
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.
hinkley
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.
elchananHaas
The layman's answer is that since everywhere was very dense there wasn't a gravitational pull to one direction or another since it all cancelled out.
btilly
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.
pizzathyme
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.
psunavy03
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.
stouset
I think the concern is that if a star was headed in our direction we’d see it coming. We don’t see one, so we know there is no anticipated threat.
A small, lone black hole could be on an intersecting trajectory with us within a few years and we’d be completely oblivious.
snowwrestler
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!
Ancalagon
As if there were any different actions that could be taken to avoid a star vs a black hole.
I’d probably welcome the quicker demise tbh
hinkley
If we saw a star coming toward us...
Have you seen the Walking Dead?
null
louthy
We’d see the lensing soon enough, but couldn’t do anything about it
pixl97
I wonder if a few solar mass black hole would bend light far enough around it that it would show up at some point.
With all that said, maybe it's better off if we were completely oblivious.
jonah-archive
Fritz Leiber, "A Pail of Air": https://www.gutenberg.org/cache/epub/51461/pg51461-images.ht...
gmuslera
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.
omnibrain
> Cosmos 1999
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).
Mountain_Skies
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.
deadbabe
He technically did not say the invisible monster was a black hole.
thangalin
> gobble planets and stars
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.
vanattab
Where is the 250 million years come from?
ftrobro
Perhaps a reference to Pangea Proxima?
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.
SllX
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.
danparsonson
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.
SllX
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.
ajb
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.
sega_sai
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.
rad_gruchalski
Would we notice if it was to point in our direction?
hnuser123456
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.
tejtm
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)
casenmgreen
In practical terms, not so very far away from the NEAs that we have no idea of, and which we notice after they've just skimmed by the Earth.
cogman10
I'm sure I'm not the only one that's thought of this, but could this be "dark matter"? Is the universe simply filled with these rouge black holes?
tomrod
> rouge black holes
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!
cogman10
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.
saltcured
But are there enough of them that we're really the rogue matter that is abnormal?
hinkley
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.
danparsonson
These would be 'primordial' black holes: https://en.m.wikipedia.org/wiki/Primordial_black_hole
nabakin
That was my first thought too. A cursory search indicates we would see a lot more gravitational lensing in our observations if that was the case.
Found a couple of videos on it too
MattPalmer1086
There are some theories that primordial black holes could be dark matter. It's not a mainstream view though.
7thaccount
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.
nxpnsv
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.
YeGoblynQueenne
You'd be "lone" too if you ate all your neighbours.
> 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